//! File → Place: another file's art into the active document as one undo step that never touches
//! the clipboard.
//!
//! - A raster image becomes one image at 100% of its physical size: its pixels at the resolution
//!   the file declares ([`fileio::ppi`]; 72 ppi when it declares none), linked to its file with
//!   `link` ([`super::links`]).
//! - An SVG becomes one group of its art; so does a DXF drawing, read with the DXF options
//!   (`dxf`, [`fileio::dxfimport`]).
//! - An EMF or WMF picture becomes one group, clipped to its frame (`crop: "crop"`) or bounded by
//!   its art (`crop: "bounding"`).
//! - An EPS file (or a PostScript .ai) becomes one group, clipped to its bounding box or bounded by
//!   its art: the document an EPS file of ours carries, else what its PostScript draws, else its
//!   preview ([`fileio::load`]).
//! - A PDF/.ai/.ait page or a native document's artboard becomes one group, clipped to the page
//!   (`crop: "crop"`; a PDF page's `art`, `trim`, `bleed` or `media` box too) or bounded by its art
//!   (`crop: "bounding"`). With Link, a PDF/.ai/.ait page placed from a file becomes a placed
//!   document instead, as a VectorCraft document does (below).
//! - A text file becomes area type, decoded and cleaned up with the Text Import Options (`text`,
//!   [`text`]).
//! - An RTF file becomes area type with its character and paragraph formatting ([`rtf`]).
//! - A Word document (`.docx`) becomes area type with the character and paragraph formatting its
//!   styles and direct formatting give ([`docx`]).
//! - A VectorCraft document placed from a file with Link (the default) becomes a placed document:
//!   one locked object showing the artboard `page`, linked to the file and read again when it
//!   changes ([`document`]); without Link, an editable copy of its art.
//!
//! The art lands centred on `at`, fitted into `rect`, or (Replace) where the replaced object was,
//! with its transform; Template puts it on a new template layer. The images, symbols, patterns and
//! swatches it uses join the document ([`adopt`]). `file.place.queue` loads the place cursor (the
//! `place` tool) with several files, which emits one `file.place` per click or drag.

pub(crate) mod adopt;
pub(crate) mod document;
pub(crate) mod docx;
mod rtf;
mod text;

use std::sync::Arc;

use serde_json::{Value, json};
use vectorcraft_color::Paint;
use vectorcraft_doc::{Appearance, Document, ImageObject, LinkInfo, Node, NodeId, NodeKind, PageBox, Scaling, SymbolBoxes};
use vectorcraft_geom::{Affine, Point, Rect, shapes};
use vectorcraft_pdf::CropTo;

use super::fileio::{self, Format, RasterImage};
use super::{CommandSpec, Result, Session, always, bad, bool_or, cmd, finite_numbers, has_doc, id_param, str_param, unique_name};
use crate::{EngineError, MAX_COORD};

const PLACE: &str = "file.place";
const QUEUE: &str = "file.place.queue";
/// The most files one `file.place.queue` loads.
const MAX_QUEUE: usize = 100;
/// The longest thumbnail side `thumbnail` may ask for (px).
const MAX_THUMBNAIL: f64 = 512.0;
/// A text file's natural box (`file.place.info`, the place cursor): a letter page less 1 in margins.
const TEXT_FRAME: Rect = Rect::new(0.0, 0.0, 468.0, 648.0);

pub fn specs() -> Vec<CommandSpec> {
    vec![
        cmd!(
            "file.place",
            "Place…",
            ["File"],
            Some("Cmd+Shift+P"),
            "{path | name | dataBase64 (a file's path, or its name with its bytes), link?: true (a raster image keeps its file's path; a VectorCraft document at path becomes one locked placed document showing artboard `page`, linked to the file and read again when it changes (links.update; saving it in this app updates it at once), drawn as vectors in every output; so does a PDF/.ai page at path, showing its `crop` box, unless password or textAs: \"outlines\" is given; false: an editable copy of its art, as from dataBase64; other files are embedded), text?: {characterSet?: \"unicode\" (UTF-8, or UTF-16 with a byte-order mark; other bytes as the platform's 8-bit set) | \"ansi\" (the platform's 8-bit set), platform?: \"windows\" (Windows-1252) | \"mac\" (Mac Roman), removeLineReturns?: false (each block of lines becomes one paragraph; blank lines end paragraphs), removeParagraphReturns?: false (drop blank lines), replaceSpaces?: n (runs of n ≥ 2 spaces become a tab)} (a .txt file, placed as area type filling rect, the replaced object's bounds, or else the artboard less a 36 pt margin), template?: false (onto a new locked template layer below the current layer), replace?: false (swap the one selected object, keeping its stacking place and transform; no at/rect), at?: [x, y] centre (default: the first artboard's centre), rect?: [x, y, width, height] fit inside; aspect kept (wins over at), page?: 1 (PDF/.ai page, or a native document's artboard), crop?: \"crop\" (clipped to that page or artboard, default; an SVG, only when given: framed and clipped by its viewBox, else by its art's bounds) | \"bounding\" (the bounds of the art that shows, with its strokes and effects, as an export measures them: hidden objects and guides left out) | \"art\" | \"trim\" | \"bleed\" | \"media\" (a PDF page's boxes), password? (an encrypted PDF), dxf?: {…the DXF options of document.open} (a .dxf drawing: fit fills the artboard under at, else the first; fitted or uncentred art lands with its drawing's artboard on that artboard, else it is centred on at)} → {ids, name, format, linked, width, height, warnings}. Raster images come in at 100% of their physical size (the file's ppi, else 72); SVG, DXF, PDF/.ai, EMF/WMF (clipped to the picture's frame), EPS (clipped to its bounding box; as document.open reads it), a .ai saved without PDF compatibility (from its editing data, as document.open reads it: the art of the layers that show on artboard `page`, clipped to that artboard unless crop is \"bounding\") and native documents as one group, with the images, symbols, patterns and swatches they use. One undo step; selects what it placed (unless on a template layer); never touches the clipboard. A PNG, JPEG, GIF or WebP image whose pixels can't be read (a file cut short) is an error, and nothing is placed",
            has_doc,
            place
        ),
        cmd!(
            query "file.place.info",
            "Placed File Info",
            [],
            None,
            "{path | name | dataBase64 (a file's path, or its name with its bytes), page?, crop?, password?, thumbnail?: px, link?: bool, dxf?: {…} (both as file.place)} what file.place would place, without placing it → {name, format, width, height (pt at 100%), pixelWidth?, pixelHeight?, ppi?: [x, y], colorMode?: RGB|Grayscale|CMYK (raster images), warnings, thumbnailBase64?: PNG of at most `thumbnail` (≤ 512) px on its longer side}",
            always,
            info
        ),
        cmd!(
            query "image.info",
            "Image Info",
            [],
            None,
            "{id?} an image object (default: the one selected) → {id, name, linked, link, colorMode: RGB|Grayscale|CMYK, pixelWidth, pixelHeight, ppi: [x, y] at its placed size, width, height}",
            has_doc,
            image_info
        ),
        cmd!(
            query "file.place.queue",
            "Load Place Cursor",
            [],
            None,
            "{paths?: [path…], files?: [{name, dataBase64}…], link?, template?, page?, crop?, text?, dxf?, thumbnail?: px} load the place cursor (the `place` tool) with up to 100 files (as file.place reads them): a click places the current file at 100% with its top-left corner there, a drag places it at the dragged size (aspect kept), ←/→ and ↑/↓ cycle the files, Esc discards the current one; each placement is a file.place, and the previous tool returns after the last → {count, files: [{name, format, width, height, thumbnailBase64?}], skipped: [{name, error}]}",
            has_doc,
            queue
        ),
    ]
}

// ---------- reading the file ----------

/// A file's art at its natural size, before it joins a document.
enum Art {
    Image(RasterImage),
    /// A text file's, an RTF file's or a Word document's text, placed as area type filling the
    /// natural box.
    Text(text::Story),
    /// A VectorCraft document or a PDF/.ai page placed linked: the file read, the link, and
    /// whether the art's bounds (not the artboard or page) are shown.
    Document(document::Source, LinkInfo, bool),
    Vector {
        /// The loaded document: the source of the art's resources.
        src: Box<Document>,
        nodes: Vec<Node>,
        /// Crop: the page or artboard the art is clipped to.
        clip: Option<Rect>,
    },
}

struct Loaded {
    /// The file name (the placed object's name).
    name: String,
    format: &'static Format,
    art: Art,
    /// The art's natural box (what `at` centres and `rect` fits).
    natural: Rect,
    warnings: Vec<String>,
    /// The link to a raster image's file or a placed document's (for Link), when read from a path.
    link: Option<LinkInfo>,
    /// The artboard a DXF drawing fitted to an artboard, or not centred, was laid out on: it lands
    /// on the target artboard the same way.
    board: Option<Rect>,
}

/// Points per pixel of a raster image at the resolution it declares (72 ppi when none).
pub(crate) fn pt_per_px(ppi: Option<(f64, f64)>) -> (f64, f64) {
    let (x, y) = ppi.unwrap_or((72.0, 72.0));
    (72.0 / x, 72.0 / y)
}

/// The file `p` names, read into placeable art; a DXF drawing's Fit to Artboard fills `board`
/// (unless the params name their own box). A PDF/.ai page read from a path is placed linked with
/// Link when `link_pdf` (false for the queries, which read it embedded).
fn load(p: &Value, cmd: &str, board: Option<Rect>, link_pdf: bool) -> Result<Loaded> {
    let src = fileio::source(p, cmd)?;
    let name = fileio::file_name(src.name);
    // An Affinity file is recognised by its signature, whatever its name says.
    if fileio::TEXT_EXTS.contains(&fileio::extension(src.name).as_str()) && !vectorcraft_affinity::is_affinity(&src.bytes) {
        let text = text::import(&src.bytes, text::TextOptions::parse(p, cmd)?, cmd)?;
        if text.trim().is_empty() {
            return Err(bad(cmd, format!("`{name}` has no text to place")));
        }
        let art = Art::Text(text::Story::plain(text));
        return Ok(Loaded { name, format: &text::FORMAT, art, natural: TEXT_FRAME, warnings: vec![], link: None, board: None });
    }
    // An RTF file is recognized by its content, whatever its name says (a .txt file is plain text).
    if rtf::is_rtf(&src.bytes) {
        let story = rtf::import(&src.bytes, cmd)?;
        if story.plain_text().trim().is_empty() {
            return Err(bad(cmd, format!("`{name}` has no text to place")));
        }
        return Ok(Loaded { name, format: &rtf::FORMAT, art: Art::Text(story), natural: TEXT_FRAME, warnings: vec![], link: None, board: None });
    }
    // A Word document is recognized by its name or by its package's `word/document.xml`.
    if docx::is_docx(src.name, &src.bytes) {
        let story = docx::import(&src.bytes, cmd)?;
        if story.plain_text().trim().is_empty() {
            return Err(bad(cmd, format!("`{name}` has no text to place")));
        }
        return Ok(Loaded { name, format: &docx::FORMAT, art: Art::Text(story), natural: TEXT_FRAME, warnings: vec![], link: None, board: None });
    }
    let format = fileio::detect(src.name, &src.bytes)
        .ok_or_else(|| bad(cmd, format!("can't place `{name}`: not a format VectorCraft reads (see document.formats)")))?;
    let page = match p.get("page") {
        None => 1,
        Some(v) => v.as_u64().filter(|n| (1..=100_000).contains(n)).ok_or_else(|| bad(cmd, "page must be a whole number from 1"))? as usize,
    };
    let mut opts = fileio::LoadOptions::from_params(cmd, p)?;
    if let Some(b) = board
        && p.get("dxf").and_then(|d| d.get("fitTo")).is_none()
    {
        opts.dxf.fit_to = (b.width(), b.height());
    }
    // PostScript .ai files are read like EPS.
    let pdf = matches!(format.id, "pdf" | "ai" | "ait") && !vectorcraft_pdf::is_postscript(&src.bytes);
    if !pdf && !matches!(opts.crop, CropTo::Crop | CropTo::Bounding) {
        return Err(bad(
            cmd,
            format!("crop `{}`: only PDF pages have art, trim, bleed and media boxes; use \"crop\" or \"bounding\"", opts.crop.id()),
        ));
    }
    let crop = opts.crop != CropTo::Bounding;
    // A VectorCraft document: placed linked from its file, else as an editable copy.
    if matches!(format.id, "vectorcraft" | "template") {
        let page = page as u32;
        if let Some(path) = src.path.filter(|_| bool_or(p, "link", true)) {
            let s = document::source(src.name, &src.bytes, Some(path), page, !crop, PageBox::Crop, cmd)?;
            let link = LinkInfo { page: Some(page), ..super::links::link_info(path, &src.bytes) };
            let (natural, warnings) = (s.frame, s.warnings.clone());
            return Ok(Loaded { name, format, art: Art::Document(s, link.clone(), !crop), natural, warnings, link: Some(link), board: None });
        }
        let a = document::document_art(src.name, &src.bytes, src.path, page, !crop, PageBox::Crop, cmd)?;
        let art = Art::Vector { src: Box::new(a.doc), nodes: a.nodes, clip: a.clip };
        return Ok(Loaded { name, format, art, natural: a.frame, warnings: a.warnings, link: None, board: None });
    }
    if format.raster {
        let img = fileio::raster_image(&src.bytes)?;
        let (sx, sy) = pt_per_px(img.ppi);
        let natural = Rect::new(0.0, 0.0, img.width as f64 * sx, img.height as f64 * sy);
        let link = src.path.map(|path| super::links::link_info(path, &src.bytes));
        let warnings = fileio::size_note(&img.blob.bytes).into_iter().collect();
        return Ok(Loaded { name, format, art: Art::Image(img), natural, warnings, link, board: None });
    }
    if pdf {
        // Linked: placed like a VectorCraft document, read again with the page's box only. A page
        // asked for with a password or with its text as outlines is embedded.
        let linked = link_pdf && bool_or(p, "link", true) && opts.password.is_none() && opts.text_as == vectorcraft_pdf::TextAs::Text;
        if let Some(path) = src.path.filter(|_| linked) {
            let page = page as u32;
            let s = document::source(src.name, &src.bytes, Some(path), page, !crop, document::page_box(opts.crop), cmd)?;
            let link = LinkInfo { page: Some(page), ..super::links::link_info(path, &src.bytes) };
            let (natural, warnings) = (s.frame, s.warnings.clone());
            return Ok(Loaded { name, format, art: Art::Document(s, link.clone(), !crop), natural, warnings, link: Some(link), board: None });
        }
        let a = pdf_art(src.name, &src.bytes, src.path, page, opts, !crop, cmd)?;
        let art = Art::Vector { src: Box::new(a.doc), nodes: a.nodes, clip: a.clip };
        return Ok(Loaded { name, format, art, natural: a.frame, warnings: a.warnings, link: None, board: None });
    }
    let anchored = format.id == "dxf" && (opts.dxf.fit || !opts.dxf.center);
    let (mut doc, warnings) = {
        // Of the open options, only a DXF drawing's apply (the colour mode stays the file's).
        let o = fileio::LoadOptions { dxf: opts.dxf, ..Default::default() };
        let mut l = fileio::load_with(src.name, &src.bytes, &o)?;
        // An Affinity file whose native document couldn't be read is only its preview: it
        // must never silently stand in for the art.
        if l.preview_only {
            return Err(bad(
                cmd,
                format!(
                    "{name}: only this Affinity file's embedded preview could be read; use File › Open to see it with its warning, or export SVG or PDF from Affinity before placing"
                ),
            ));
        }
        // Linked images show their files, found from its folder.
        super::links::resolve(&mut l.doc, src.path, false, false);
        (l.doc, l.warnings)
    };
    doc.drop_edit_modes();
    let board = doc.artboards.first().map(|a| a.rect).filter(|_| anchored);
    let layers = std::mem::take(&mut doc.layers);
    let symbols = doc.symbol_boxes();
    let (nodes, clip) = if matches!(format.id, "svg" | "svgz" | "dxf") {
        // An SVG with `crop: "crop"` asked for is framed and clipped by its viewBox (its artboard),
        // as a PDF by its page: art drawn on a shared canvas keeps its place and scale (#788). By
        // default, as Illustrator places one, it is its art's bounds.
        let framed = matches!(format.id, "svg" | "svgz") && crop && p.get("crop").is_some();
        let frame = doc.artboards.first().map(|a| a.rect).filter(|_| framed);
        (art_of(layer_art(&layers)), frame)
    } else {
        let n = doc.artboards.len();
        let board = doc.artboards.get(page - 1).map(|a| a.rect).ok_or_else(|| bad(cmd, format!("page {page}: `{name}` has {n} page(s)")))?;
        // An EPS file's art is whatever lies on the artboard.
        (on_artboard(&symbols, &layers, board), crop.then_some(board))
    };
    let natural = clip.or_else(|| shown_bounds(&symbols, &nodes));
    let natural = natural.filter(|r| r.width() > 0.0 || r.height() > 0.0).ok_or_else(|| bad(cmd, format!("`{name}` has no art to place")))?;
    Ok(Loaded { name, format, art: Art::Vector { src: Box::new(doc), nodes, clip }, natural, warnings, link: None, board })
}

/// Page `page` (1-based) of the PDF/.ai/.ait file `src` (`bytes`, read from `path` when there is
/// one) as art to place: clipped to the box `opts.crop` names, or (`bounding`) the bounds of its
/// art; read with `opts.password`. Only the page placed is read. A .ai saved without PDF
/// compatibility is read from its editing data, as it opens, and placed as an EPS is: the art on
/// artboard `page`, its linked images found from its folder.
pub(crate) fn pdf_art(
    src: &str,
    bytes: &[u8],
    path: Option<&str>,
    page: usize,
    opts: fileio::LoadOptions,
    bounding: bool,
    cmd: &str,
) -> Result<document::DocumentArt> {
    let name = fileio::file_name(src);
    let index = page.checked_sub(1).ok_or_else(|| bad(cmd, "page must be a whole number from 1"))?;
    let o = fileio::LoadOptions { crop: if bounding { CropTo::Crop } else { opts.crop }, ..opts };
    let mut read = fileio::page_document(bytes, index, &o);
    // Such a file can have more artboards than placeholder pages.
    if page > 1
        && read.is_err()
        && let Err(e) = fileio::page_document(bytes, 0, &o)
        && fileio::is_placeholder(&e)
    {
        read = Err(e);
    }
    let (mut doc, warnings, alone) =
        fileio::page_or_editing_data(src, bytes, o.password.as_deref(), read).map_err(|e| bad(cmd, format!("{name}: {e}")))?;
    if alone {
        // Linked images show their files, found from its folder.
        super::links::resolve(&mut doc, path, false, false);
    }
    doc.drop_edit_modes();
    let layers = std::mem::take(&mut doc.layers);
    let symbols = doc.symbol_boxes();
    // The page placed is a PDF import's only one, with one layer; the editing data's art is
    // whatever lies on the artboard.
    let index = if alone { index } else { 0 };
    let n = doc.artboards.len();
    let board = doc.artboards.get(index).map(|a| a.rect).ok_or_else(|| bad(cmd, format!("page {page}: `{name}` has {n} page(s)")))?;
    let pages = if alone { &layers[..] } else { layers.get(index..=index).unwrap_or_default() };
    let nodes = on_artboard(&symbols, pages, board);
    let clip = (!bounding).then_some(board);
    let frame = clip.or_else(|| shown_bounds(&symbols, &nodes));
    let frame = frame.filter(|r| r.width() > 0.0 || r.height() > 0.0).ok_or_else(|| bad(cmd, format!("`{name}` has no art to place")))?;
    Ok(document::DocumentArt { doc, nodes, clip, frame, warnings })
}

/// The bounds of what `nodes` draw, as an export measures art
/// ([`vectorcraft_render::encode::drawn_bounds`]): hidden objects, guides and template layers
/// left out, symbol instances measured by their art in `symbols`.
pub(crate) fn shown_bounds(symbols: &SymbolBoxes, nodes: &[Node]) -> Option<Rect> {
    nodes.iter().fold(None, |acc, n| vectorcraft_geom::union_opt(acc, vectorcraft_render::encode::drawn_bounds(symbols, n)))
}

/// The placeable art of `layers` that lies on `board`: each object whose drawn bounds
/// ([`vectorcraft_render::encode::drawn_bounds`]) lie on it, or, for an object that draws nothing,
/// each object whose visual bounds lie on it.
fn on_artboard(symbols: &SymbolBoxes, layers: &[Arc<Node>], board: Rect) -> Vec<Node> {
    let on_board = |c: &&Arc<Node>| {
        let b = vectorcraft_render::encode::drawn_bounds(symbols, c).or_else(|| c.visual_bounds_with(symbols));
        b.is_some_and(|b| b.intersect(board).area() > 0.0 || board.contains(b.origin()))
    };
    art_of(layer_art(layers).filter(on_board))
}

/// The objects of the placeable `layers`, a clipping layer as itself: its objects alone would lose
/// their clip, and its clipping path would come in as a loose path.
fn layer_art(layers: &[Arc<Node>]) -> impl Iterator<Item = &Arc<Node>> {
    layers.iter().filter(|l| placeable(l)).flat_map(|l| match &l.kind {
        NodeKind::Layer { clip: true, .. } => std::slice::from_ref(l),
        _ => l.children().map_or(&[][..], Vec::as_slice),
    })
}

/// A clipping path of rectangle `r`, with id `id`.
fn clip_path(id: NodeId, r: Rect) -> Node {
    let mut c = Node::path(id, shapes::rectangle(r), Appearance::basic(Paint::None, Paint::None, 0.0));
    if let NodeKind::Path { clipping, .. } = &mut c.kind {
        *clipping = true;
    }
    c
}

/// A visible, non-template layer.
fn placeable(l: &Node) -> bool {
    l.visible && !matches!(l.kind, NodeKind::Layer { template: true, .. })
}

/// The placeable art among `nodes`: guides left out, visible sublayers as groups (clip groups for
/// clipping layers).
fn art_of<'a>(nodes: impl Iterator<Item = &'a Arc<Node>>) -> Vec<Node> {
    nodes
        .filter_map(|c| match &c.kind {
            NodeKind::Path { guide: true, .. } => None,
            NodeKind::Layer { children, clip, .. } => placeable(c).then(|| {
                let mut g = (**c).clone();
                g.kind = NodeKind::Group { children: art_of(children.iter()).into_iter().map(Arc::new).collect(), clip: *clip };
                g
            }),
            _ => Some((**c).clone()),
        })
        .collect()
}

/// The art as one object of `d` (its resources added), at its natural size and position.
fn build(d: &mut Document, l: Loaded, link: Option<LinkInfo>) -> Node {
    let mut node = match l.art {
        Art::Image(img) => {
            let (sx, sy) = pt_per_px(img.ppi);
            super::links::store_image(d, &img.key, img.blob, link.is_some());
            let im = ImageObject {
                key: img.key,
                width: img.width,
                height: img.height,
                xf: Affine::scale_non_uniform(sx, sy),
                link,
                placement: Default::default(),
                pixels: None,
            };
            Node::new(d.alloc_id(), NodeKind::Image(Box::new(im)))
        }
        Art::Text(t) => Node::new(d.alloc_id(), NodeKind::Text(Box::new(text::area_text(t, l.natural, &d.setup)))),
        Art::Document(s, link, bounding) => document::node(d, &s, link, bounding),
        Art::Vector { src, mut nodes, clip } => {
            adopt::adopt(d, &src, &mut nodes);
            let mut children: Vec<Arc<Node>> = nodes.iter().map(|n| Arc::new(d.reid(n))).collect();
            if let Some(r) = clip {
                children.insert(0, Arc::new(clip_path(d.alloc_id(), r)));
            }
            Node::new(d.alloc_id(), NodeKind::Group { children, clip: clip.is_some() })
        }
    };
    node.name = Some(l.name);
    node
}

/// `node` moved and scaled by `m` as a whole: strokes, effects and pattern tiles go along.
pub(crate) fn transformed(mut node: Node, m: Affine) -> Node {
    node.transform(m, Scaling { strokes: true, effects: Some(vectorcraft_render::effects::scale_effect), ..Default::default() });
    adopt::each_mut(&mut node, &mut |n| vectorcraft_doc::pattern::transform_pattern_paints(n, m));
    node
}

// ---------- file.place ----------

/// `[x, y, width, height]` with a positive size.
fn rect_param(p: &Value) -> Result<Option<Rect>> {
    let Some(v) = p.get("rect") else { return Ok(None) };
    // All four or nothing: a malformed entry dropped would shift the others ([0, "bad", 10, 40, 50]).
    match finite_numbers(v) {
        Some([x, y, w, h]) if w > 0.0 && h > 0.0 => Ok(Some(Rect::new(x, y, x + w, y + h))),
        _ => Err(bad(PLACE, "rect must be [x, y, width, height] with a positive width and height")),
    }
}

/// `at`, the `[x, y]` the art is centred on (absent or null: none); anything else fails rather than
/// placing the art as if no point were given.
fn at_param(p: &Value) -> Result<Option<Point>> {
    p.get("at")
        .filter(|v| !v.is_null())
        .map(|v| finite_numbers(v).map(|[x, y]| Point::new(x, y)).ok_or_else(|| bad(PLACE, "at must be [x, y]")))
        .transpose()
}

/// The transform that puts new art with the natural box `natural` where `old` is: an image's scale
/// and rotation relative to its 100% size (its resolution's) and its centre are kept (with
/// `image_xf`); other objects keep their centre.
fn replace_xf(d: &Document, old: &Node, natural: Rect, image_xf: bool) -> Affine {
    if image_xf && let NodeKind::Image(im) = &old.kind {
        let (sx, sy) = pt_per_px(d.images.get(&im.key).and_then(|b| fileio::ppi::resolution(&b.bytes)));
        let full = Affine::scale_non_uniform(sx, sy);
        let centre = full * Point::new(im.width as f64 / 2.0, im.height as f64 / 2.0);
        if im.xf.determinant().abs() > 1e-12 {
            return im.xf * full.inverse() * Affine::translate(centre - natural.center());
        }
    }
    let c = old.geometric_bounds_with(&d.symbol_boxes()).map_or(natural.center(), |b| b.center());
    Affine::translate(c - natural.center())
}

/// `rect` fitted with `natural`'s aspect, centred.
fn fit(natural: Rect, r: Rect) -> Affine {
    let ratio = |a: f64, b: f64| (b > 1e-9).then(|| a / b);
    let k = [ratio(r.width(), natural.width()), ratio(r.height(), natural.height())].into_iter().flatten().reduce(f64::min).unwrap_or(1.0);
    Affine::translate(r.center().to_vec2()) * Affine::scale(k) * Affine::translate(-natural.center().to_vec2())
}

/// What `file.place` takes from the session before it reads the file: the params, the object
/// Replace swaps and the artboard under `at`, which a DXF drawing is laid out on
/// ([`Session::prepare_place`]). [`PlaceJob::read`] reads and decodes the file without the session,
/// on any thread.
pub struct PlaceJob {
    params: Value,
    old: Option<NodeId>,
    /// The object Replace swaps as it was when Place started.
    replaced: Option<Node>,
    target: Option<Rect>,
}

/// A file [`PlaceJob::read`] read, which [`Session::place_read`] places.
pub struct PlaceRead {
    job: PlaceJob,
    loaded: Loaded,
}

impl PlaceJob {
    /// The name of the file it places ("photo.tif").
    pub fn name(&self) -> String {
        str_param(&self.params, "path").or_else(|| str_param(&self.params, "name")).map(fileio::file_name).unwrap_or_else(|| "Untitled".into())
    }

    /// Read and decode the file, as `file.place` does, without the session. The pixels of a PNG,
    /// JPEG, GIF or WebP file are decoded here to check that they can be read (an error when they
    /// can't), a linked image's preview is made from that decode, and the decoded pixels are kept in
    /// the renderers' image store for the first frame that draws them
    /// ([`super::links::readable_and_kept`]).
    pub fn read(self) -> Result<PlaceRead> {
        let mut loaded = load(&self.params, PLACE, self.target, true)?;
        let linked = loaded.link.is_some() && bool_or(&self.params, "link", true);
        if let Art::Image(img) = &mut loaded.art {
            let unread = super::links::kept_unread(&img.blob.bytes);
            img.blob = super::links::readable_and_kept(img.blob.clone(), unread, linked)?;
        }
        Ok(PlaceRead { job: self, loaded })
    }
}

impl Session {
    /// `file.place`'s checks (with no document open, the error `file.place` gives) of `params`
    /// against the active document as it is now → what reads the file ([`PlaceJob::read`]; on the
    /// desktop File › Place does this off the UI thread). Replace swaps the object selected now;
    /// the art is placed against the artboard under `at` as it is when [`Session::place_read`]
    /// places it.
    pub fn prepare_place(&self, params: &Value) -> Result<PlaceJob> {
        has_doc(self).map_err(|why| EngineError::Disabled(PLACE.into(), why))?;
        prepare(self, params)
    }

    /// Run `file.place` with the params of `read` as a command (checked and journaled as any
    /// other) that places the file `read` holds instead of reading it again → `file.place`'s
    /// reply. The object Replace swaps must still be in the document as it was when Place started;
    /// when the selection changed meanwhile, `select.set` selects that object again first, so a
    /// replay of the journal replaces the same object.
    pub fn place_read(&mut self, read: PlaceRead) -> Result<Value> {
        let params = read.job.params.clone();
        if let Some(old) = read.job.old {
            let st = self.doc()?;
            // Deleted, changed, or another object with its id: an undo that removes the object frees
            // its id for the next object made.
            if st.doc.node(old) != read.job.replaced.as_ref() {
                return Err(bad(PLACE, "replace: the object to replace was changed or deleted"));
            }
            if st.selection.objects != [old] {
                self.execute("select.set", &json!({ "ids": [old.0] }))?;
            }
        }
        self.place_hand_off = Some(read);
        let r = self.execute(PLACE, &params);
        self.place_hand_off = None;
        r
    }
}

fn place(s: &mut Session, p: &Value) -> Result<Value> {
    let read = match s.place_hand_off.take() {
        Some(read) => read,
        None => prepare(s, p)?.read()?,
    };
    apply(s, read)
}

fn prepare(s: &Session, p: &Value) -> Result<PlaceJob> {
    let replace = bool_or(p, "replace", false);
    let template = bool_or(p, "template", false);
    let at = at_param(p)?;
    let rect = rect_param(p)?;
    if replace && (template || at.is_some() || rect.is_some()) {
        return Err(bad(PLACE, "replace keeps the replaced object's place and transform: drop template, at and rect"));
    }
    let corners = [at, rect.map(|r| r.origin()), rect.map(|r| Point::new(r.x1, r.y1))];
    if corners.iter().flatten().any(|c| !(c.x.abs() <= MAX_COORD && c.y.abs() <= MAX_COORD)) {
        return Err(bad(PLACE, "at/rect lie outside the canvas"));
    }
    let st = s.doc()?;
    let old = match (replace, &st.selection.objects[..]) {
        (false, _) => None,
        (true, [id]) => Some(*id),
        (true, _) => return Err(bad(PLACE, "replace: select the one object to replace")),
    };
    let replaced = old.and_then(|id| st.doc.node(id)).cloned();
    Ok(PlaceJob { params: p.clone(), old, replaced, target: board_at(&st.doc, at) })
}

/// Place the file `read` holds in the active document.
fn apply(s: &mut Session, read: PlaceRead) -> Result<Value> {
    let PlaceRead { job: PlaceJob { params, old, target: read_for, .. }, mut loaded } = read;
    let p = &params;
    let template = bool_or(p, "template", false);
    let at = at_param(p)?;
    let rect = rect_param(p)?;
    let st = s.doc()?;
    let old_node = match old {
        Some(id) => Some(st.doc.node(id).ok_or_else(|| bad(PLACE, "replace: the object to replace was changed or deleted"))?),
        None => None,
    };
    // The artboard under `at` as it is now, as a replay of the journal finds it: a DXF drawing laid
    // out on the artboard it was read for is read again when that artboard changed meanwhile.
    let target = board_at(&st.doc, at);
    if loaded.board.is_some() && target != read_for {
        loaded = load(p, PLACE, target, true)?;
    }
    // Type reflows rather than scales: its frame takes the size it is placed at.
    let is_text = matches!(loaded.art, Art::Text(_));
    if is_text {
        let size = match (old_node.and_then(|o| o.geometric_bounds_with(&st.doc.symbol_boxes())), rect) {
            (Some(b), _) => b.size(),
            (None, Some(r)) => r.size(),
            (None, None) => text_frame(target).size(),
        };
        loaded.natural = Rect::from_origin_size(Point::ORIGIN, size);
    }
    let natural = loaded.natural;
    let m = match (old_node, rect) {
        (Some(o), _) => replace_xf(&st.doc, o, natural, !is_text),
        (None, Some(r)) => fit(natural, r),
        // Its artboard's bottom-left corner on the target's.
        (None, None) if let (Some(src), Some(to)) = (loaded.board, target) => Affine::translate((to.x0 - src.x0, to.y1 - src.y1)),
        (None, None) => {
            let c = at.or_else(|| st.doc.artboards.first().map(|a| a.rect.center())).unwrap_or_default();
            Affine::translate(c - natural.center())
        }
    };
    let parent = st.insertion_parent();
    let below = st.current_layer().or_else(|| parent.and_then(|p| st.doc.layer_of(p)));
    let link = loaded.link.take().filter(|_| bool_or(p, "link", true));
    let linked = link.is_some();
    let (name, format, warnings) = (loaded.name.clone(), loaded.format.id, std::mem::take(&mut loaded.warnings));
    let (id, size) = s.edit("Place", |d, sel| {
        let node = transformed(build(d, loaded, link), m);
        let size = node.geometric_bounds_with(&d.symbol_boxes()).unwrap_or_default();
        let (into, index) = match old {
            Some(old) => {
                let (par, idx, _) = d.position(old).ok_or(EngineError::NoNode(old))?;
                d.remove(old)?;
                (par, idx)
            }
            None if template => (Some(template_layer(d, below, &name)?), usize::MAX),
            None => (parent, usize::MAX),
        };
        let id = d.insert(into, index, node)?;
        // Template art is locked: nothing to select.
        if template {
            sel.clear()
        } else {
            sel.set([id])
        }
        Ok((id, size))
    })?;
    Ok(
        json!({ "ids": [id.0], "name": name, "format": format, "linked": linked, "width": size.width(), "height": size.height(), "warnings": warnings }),
    )
}

/// The artboard under `at` (its edges included, [`Document::artboard_holding`]), else the first.
fn board_at(d: &Document, at: Option<Point>) -> Option<Rect> {
    at.and_then(|c| d.artboard_holding(c, false)).and_then(|i| d.artboards.get(i)).or(d.artboards.first()).map(|a| a.rect)
}

/// Placed type's frame without `rect` or Replace: the artboard `board` (the one under `at`, else the
/// first, [`board_at`]) less a 36 pt margin.
fn text_frame(board: Option<Rect>) -> Rect {
    let board = board.unwrap_or(TEXT_FRAME);
    Rect::from_center_size(board.center(), ((board.width() - 72.0).max(72.0), (board.height() - 72.0).max(72.0)))
}

/// A new locked template layer named after the file, right below the layer `below` (else at the
/// bottom).
fn template_layer(d: &mut Document, below: Option<NodeId>, name: &str) -> Result<NodeId> {
    let id = d.add_layer(Some(&format!("Template {name}")));
    let at = below.and_then(|b| d.layers.iter().position(|l| l.id == b)).unwrap_or(0);
    d.move_node(id, None, at)?;
    if let Some(n) = d.node_mut(id) {
        n.locked = true;
        if let NodeKind::Layer { template, .. } = &mut n.kind {
            *template = true;
        }
    }
    Ok(id)
}

// ---------- file.place.queue ----------

/// The files `file.place.queue` names, as `file.place` params.
fn queued_files(p: &Value) -> Result<Vec<Value>> {
    let list = |k: &str| p.get(k).and_then(Value::as_array).map(Vec::as_slice).unwrap_or_default();
    let mut out = vec![];
    for v in list("paths") {
        let path = v.as_str().ok_or_else(|| bad(QUEUE, "paths must be strings"))?;
        out.push(json!({ "path": path }));
    }
    for f in list("files") {
        let (Some(name), Some(data)) = (str_param(f, "name"), str_param(f, "dataBase64")) else {
            return Err(bad(QUEUE, "files must be {name, dataBase64}"));
        };
        out.push(json!({ "name": name, "dataBase64": data }));
    }
    match out.len() {
        0 => Err(bad(QUEUE, "give paths or files")),
        n if n > MAX_QUEUE => Err(bad(QUEUE, format!("at most {MAX_QUEUE} files"))),
        _ => Ok(out),
    }
}

/// The files `file.place.queue` loads the place cursor with, before they are read
/// ([`Session::prepare_place_queue`]). [`QueueJob::read`] reads them without the session, on any
/// thread.
pub struct QueueJob {
    params: Value,
    files: Vec<Value>,
}

/// The files [`QueueJob::read`] read, which [`Session::place_queue_read`] loads the place cursor
/// with.
pub struct QueueRead {
    params: Value,
    entries: Vec<Value>,
    files: Vec<Value>,
    skipped: Vec<Value>,
}

impl QueueJob {
    /// The names of the files it loads ("a.tif", "b.psd").
    pub fn names(&self) -> Vec<String> {
        self.files.iter().filter_map(|q| str_param(q, "path").or(str_param(q, "name"))).map(fileio::file_name).collect()
    }

    /// Read every file for its size and thumbnail, as `file.place.queue` does, without the session.
    pub fn read(self) -> Result<QueueRead> {
        read_queue(self.params, self.files)
    }
}

/// Read each of `queued`, the files of `file.place.queue` with params `p`, for its size and
/// thumbnail.
fn read_queue(p: Value, queued: Vec<Value>) -> Result<QueueRead> {
    let thumbnail = p.get("thumbnail").and_then(Value::as_f64);
    let (mut entries, mut files, mut skipped) = (vec![], vec![], vec![]);
    for mut q in queued {
        for k in ["link", "template", "page", "crop", "text", "dxf"] {
            if let Some(v) = p.get(k) {
                q[k] = v.clone();
            }
        }
        // Read for its size and thumbnail: each click places it with file.place, so a file whose
        // pixels file.place can't read is skipped. With a thumbnail, the decoded pixels are kept
        // so that drawing it does not decode the file again.
        let checked = load(&q, QUEUE, None, false).and_then(|mut l| {
            let linked = l.link.is_some() && bool_or(&q, "link", true);
            if let Art::Image(img) = &mut l.art {
                let unread = super::links::kept_unread(&img.blob.bytes);
                let check = if thumbnail.is_some() { super::links::readable_and_kept } else { super::links::readable };
                img.blob = check(img.blob.clone(), unread, linked)?;
            }
            Ok(l)
        });
        match checked {
            Ok(l) => {
                let (w, h) = (l.natural.width(), l.natural.height());
                let mut f = json!({ "name": l.name, "format": l.format.id, "width": w, "height": h });
                entries.push(json!({ "params": q, "name": l.name, "width": w, "height": h }));
                if let Some(px) = thumbnail {
                    f["thumbnailBase64"] = json!(thumbnail_png(l, px)?);
                }
                files.push(f);
            }
            Err(e) => {
                let name = str_param(&q, "path").or(str_param(&q, "name")).map(fileio::file_name).unwrap_or_default();
                skipped.push(json!({ "name": name, "error": e.to_string() }));
            }
        }
    }
    Ok(QueueRead { params: p, entries, files, skipped })
}

impl Session {
    /// `file.place.queue`'s checks (with no document open, the error `file.place.queue` gives) of
    /// `params` → what reads the files ([`QueueJob::read`]; on the
    /// desktop the Place dialog's OK with several files does this off the UI thread).
    pub fn prepare_place_queue(&self, params: &Value) -> Result<QueueJob> {
        has_doc(self).map_err(|why| EngineError::Disabled(QUEUE.into(), why))?;
        Ok(QueueJob { params: params.clone(), files: queued_files(params)? })
    }

    /// Run `file.place.queue` with the params of `read` as a command that loads the place cursor
    /// with the files `read` holds instead of reading them again → `file.place.queue`'s reply.
    pub fn place_queue_read(&mut self, read: QueueRead) -> Result<Value> {
        let params = read.params.clone();
        self.queue_hand_off = Some(read);
        let r = self.execute(QUEUE, &params);
        self.queue_hand_off = None;
        r
    }
}

fn queue(s: &mut Session, p: &Value) -> Result<Value> {
    let read = match s.queue_hand_off.take() {
        Some(read) => read,
        None => s.prepare_place_queue(p)?.read()?,
    };
    let QueueRead { entries, files, skipped, .. } = read;
    if entries.is_empty() {
        let why = skipped.first().and_then(|e| e["error"].as_str()).unwrap_or("nothing to place");
        return Err(bad(QUEUE, why));
    }
    // Reloading the cursor keeps the tool to return to.
    let prev = Some(s.tool_id()).filter(|t| *t != "place");
    let view = s.last_view;
    s.select_tool("place", view)?;
    s.set_tool_option("queue", &json!({ "entries": entries, "prev": prev }));
    Ok(json!({ "count": files.len(), "files": files, "skipped": skipped }))
}

// ---------- queries ----------

/// The colour mode an image file stores its pixels in.
fn color_mode(bytes: &[u8]) -> &'static str {
    use image::{ExtendedColorType as E, ImageDecoder as _};
    let kind = image::ImageReader::new(std::io::Cursor::new(bytes))
        .with_guessed_format()
        .ok()
        .and_then(|r| r.into_decoder().ok())
        .map(|d| d.original_color_type());
    match kind {
        Some(E::L1 | E::La1 | E::L2 | E::La2 | E::L4 | E::La4 | E::L8 | E::La8 | E::L16 | E::La16) => "Grayscale",
        Some(E::Cmyk8 | E::Cmyk16) => "CMYK",
        _ => "RGB",
    }
}

/// `l` rendered as a PNG at most `px` (≤ [`MAX_THUMBNAIL`]) pixels on its longer side, base64.
fn thumbnail_png(l: Loaded, px: f64) -> Result<String> {
    let natural = l.natural;
    let mut d = Document::new(natural.width().max(1.0), natural.height().max(1.0));
    let layer = d.layers.first().map(|l| l.id);
    let node = build(&mut d, l, None);
    d.insert(layer, 0, node)?;
    let k = px.clamp(1.0, MAX_THUMBNAIL) / natural.width().max(natural.height()).max(1e-9);
    let png = vectorcraft_render::Renderer::new().render_region(&d, natural, k, false).to_png().map_err(EngineError::Other)?;
    Ok(vectorcraft_format::base64_encode(&png))
}

fn info(_: &mut Session, p: &Value) -> Result<Value> {
    read_info(p)
}

/// `file.place.info` with `p`, without the session (on the desktop the Place dialog reads its
/// files' lines this way off the UI thread).
pub fn read_info(p: &Value) -> Result<Value> {
    // A PDF/.ai page linked or not has the same size and art.
    let mut l = load(p, "file.place.info", None, false)?;
    let natural = l.natural;
    let mut out = json!({
        "name": l.name,
        "format": l.format.id,
        "width": natural.width(),
        "height": natural.height(),
        "warnings": std::mem::take(&mut l.warnings),
    });
    if let Art::Image(img) = &l.art {
        let (x, y) = img.ppi.unwrap_or((72.0, 72.0));
        out["pixelWidth"] = json!(img.width);
        out["pixelHeight"] = json!(img.height);
        out["ppi"] = json!([x, y]);
        out["colorMode"] = json!(color_mode(&img.blob.bytes));
    }
    if let Some(px) = p.get("thumbnail").and_then(Value::as_f64) {
        out["thumbnailBase64"] = json!(thumbnail_png(l, px)?);
    }
    Ok(out)
}

pub(crate) fn image_info(s: &mut Session, p: &Value) -> Result<Value> {
    const C: &str = "image.info";
    let st = s.doc()?;
    let id = match (id_param(p, "id"), &st.selection.objects[..]) {
        (Some(id), _) => id,
        (None, [id]) => *id,
        _ => return Err(bad(C, "select one image or pass id")),
    };
    let n = st.doc.node(id).ok_or(EngineError::NoNode(id))?;
    let NodeKind::Image(im) = &n.kind else { return Err(bad(C, format!("object {} is not an image", id.0))) };
    // Effective resolution: 72 pt per inch over the points one pixel spans along each axis.
    let [a, b, c, d, ..] = im.xf.as_coeffs();
    let ppi = |x: f64, y: f64| Some(x.hypot(y)).filter(|l| *l > 1e-12).map_or(0.0, |l| 72.0 / l);
    let size = n.geometric_bounds().unwrap_or_default();
    Ok(json!({
        "id": id.0,
        "name": n.display_name(),
        "linked": im.link.is_some(),
        "link": im.link.as_ref().map(|l| &l.path),
        "colorMode": st.doc.images.get(&im.key).map_or("RGB", |b| color_mode(&b.bytes)),
        "pixelWidth": im.width,
        "pixelHeight": im.height,
        "ppi": [ppi(a, b), ppi(c, d)],
        "width": size.width(),
        "height": size.height(),
    }))
}