//! Library commands: publish this file as a library (to its file, or to a server for the team);
//! enable, use and update other libraries (their components, styles and variables), swap one for
//! another, and see how files use a team library.

use std::collections::BTreeSet;
use std::sync::Arc;

use figcraft_doc::*;
use serde_json::{Value, json};

use figcraft_collab::message::{LibraryReply, LibraryReq};

use super::CommandSpec;
use crate::library::*;
use crate::library_server::{archive, is_server_link, read_archive, shown_path};
use crate::live::{NetReply, NetRequest, PublishOptions};
use crate::params::*;
use crate::{EngineError, Result, Session, bad, spec};

/// Longest library description kept (chars).
const MAX_DESCRIPTION: usize = 2000;

pub fn specs() -> Vec<CommandSpec> {
    vec![
        spec!("libraries.publish", "Publish library…", "{}  (opens the publish form in the Assets panel)", false, |s, _| {
            s.request_ui("panel.libraries", json!({"publish": true}));
            Ok(json!({"ok": true}))
        }),
        spec!(
            "library.publish",
            "Publish library",
            "{description?, include? [component/set ids, style ids, variable collection ids or names: exactly these], exclude? [same]}  publishes this file's components, component sets, styles and variable collections (by default all but names starting with . or _, or what the last publish offered; variables hidden from publishing stay out unless something published uses them) as a new library version; save the file so other files see it",
            true,
            publish_cmd
        ),
        spec!(
            "library.list",
            "List libraries",
            "{assets? (also list each library's components, styles, variable collections and variables, and what this file can publish)}  → enabled libraries (version, updates, errors) and this file's published library",
            false,
            list
        ),
        spec!(
            "library.publishToServer",
            "Publish library to server",
            "{server? (an edit link of this file on a figcraft-server; omit while this file is in a live session on a server, or give the server's address with its key to keep the file there first), key?, description?, include?, exclude? (as library.publish)}  publishes the library as the next version of the one kept on the server under this file (per-asset versions as library.publish); files that enabled it with a link of the file see the update → {id, version, components, styles, collections, variables, file?, edit?, view? (links when the file was kept there now)}",
            false,
            publish_to_server
        ),
        spec!(
            "library.add",
            "Add library",
            "{path (.figcraft file published as a library, or a share link of a file on a server: a view link is enough)}",
            true,
            add
        ),
        spec!(
            "library.usage",
            "Library usage",
            "{library? (an enabled team library: id, name or link; omit for this file's library on its server)}  → what files report: {id, name, instances, files: [{name, updated, instances}], components: [{id, name, instances, files}]}",
            false,
            usage_cmd
        ),
        spec!(
            "library.swap",
            "Swap library",
            "{from (an enabled library: id, name or path), to (another enabled library)}  re-points every component instance, style and variable copied from `from` to the published one of the same name in `to` (instances keep their overrides) → {components, styles, variables, unmatched: [names still from `from`], removed (nothing of `from` is used any more: it was removed)}",
            true,
            swap_cmd
        ),
        spec!(
            "library.remove",
            "Remove library",
            "{id (library id, name or path)}  (copies still in use stay; unused ones are dropped)",
            true,
            remove
        ),
        spec!(
            "library.updates",
            "Library updates",
            "{}  → the components, styles, variable collections and variables with a newer published version, and variables new to a library collection this file extends (listed without an `id`: no copy yet)",
            false,
            updates
        ),
        spec!(
            "library.acceptUpdates",
            "Accept library updates",
            "{ids? [library ids; all when omitted]}  pulls updated components, styles, variable collections and variables in (instances keep their overrides; bound layers follow)",
            true,
            accept
        ),
        spec!(
            "library.place",
            "Place library component",
            "{library (id, name or path), component (id or name of a published component, set or variant), x?, y? (page point; default the view's centre)}",
            true,
            place
        ),
        spec!(
            "library.swapAt",
            "Swap instance to library component",
            "{library, component (id or name of a published component, set or variant), x, y (page point)}  copies the component in and swaps the instance there to it (as instance.swapAt)",
            true,
            |s, p| {
                let (_, lib, key) = component_arg(s, "library.swapAt", p)?;
                let map = import(s.doc_mut()?, &lib, &[key], false)?;
                let local = map.get(&key).copied().ok_or_else(|| EngineError::Other("the component didn't import".into()))?;
                super::component::swap_at(s, &with(p, &["x", "y"], json!({"component": local})))
            }
        ),
        spec!(
            "library.import",
            "Import library component",
            "{library, component}  → {component (local, read-only main to instantiate with instance.create)}",
            true,
            |s, p| {
                let (_, lib, key) = component_arg(s, "library.import", p)?;
                let map = import(s.doc_mut()?, &lib, &[key], false)?;
                let local = map.get(&key).copied().ok_or_else(|| EngineError::Other("the component didn't import".into()))?;
                Ok(json!({"component": local}))
            }
        ),
        spec!(
            "library.applyStyle",
            "Apply library style",
            "{library, style (id or name of a published style), ids?, target? (fill|stroke)}  copies the style in (linked, read-only) and applies it",
            true,
            apply_style
        ),
        spec!(
            "library.importVariable",
            "Import library variable",
            "{library, variable (id or name of a published variable)}  → {variable (local, read-only linked copy to use with variable.bind, or as an alias in variable.set)}",
            true,
            |s, p| {
                let (lib, key) = variable_arg(s, "library.importVariable", p, "variable")?;
                Ok(json!({"variable": import_variable(s, &lib, &key)?}))
            }
        ),
        spec!(
            "library.bindVariable",
            "Bind library variable",
            "{library, variable (id or name of a published variable), field (as variable.bind), ids?}  copies the variable in (linked, read-only) and binds it",
            true,
            |s, p| {
                let (lib, key) = variable_arg(s, "library.bindVariable", p, "variable")?;
                let local = import_variable(s, &lib, &key)?;
                super::styles::bind(s, &with(p, &["ids", "id", "field"], json!({"variable": local})))?;
                Ok(json!({"variable": local}))
            }
        ),
        spec!(
            "library.aliasVariable",
            "Alias library variable",
            "{library, alias (id or name of a published variable of the same type), variable (a local variable), mode? (default first)}  copies the library variable in (linked, read-only) and makes the local variable's value an alias of it",
            true,
            alias
        ),
        spec!(
            "library.setVariableMode",
            "Set library variable mode",
            "{library, collection (id or name of a published collection), mode (id or name), ids? (frames; the page when omitted)}  copies the collection in (linked, read-only) and sets its mode on the frames",
            true,
            set_mode
        ),
        spec!(
            "library.extendCollection",
            "Extend library collection",
            "{library, collection (id or name of a published collection), name? (default \"<name> (extended)\")}  → {id}: a collection of this file with the library collection's modes and variables (they follow its updates); override their values per mode with variable.set (variable.resetOverride goes back to the inherited value) and add variables of its own",
            true,
            extend
        ),
    ]
}

/// `base` with `p`'s values of `keys` (those it has).
fn with(p: &Value, keys: &[&str], mut base: Value) -> Value {
    for k in keys {
        if let Some(v) = get(p, k) {
            base[*k] = v.clone();
        }
    }
    base
}

/// An enabled library of the active document (`library` param), read from its file.
fn library(s: &mut Session, cmd: &str, p: &Value) -> Result<(LibraryLink, Arc<PublishedLibrary>)> {
    let key = req_string(cmd, p, "library")?;
    let link = find_link(s.doc()?, &key)
        .cloned()
        .ok_or_else(|| bad(cmd, format!("no enabled library `{key}` (library.list shows them; library.add enables one)")))?;
    let lib = s.load_library(&link.path)?;
    if lib.manifest.id != link.id {
        return Err(EngineError::Other(format!(
            "{} now holds another library (\"{}\"): remove \"{}\" and add the file again",
            shown_path(&link.path),
            lib.manifest.name,
            link.name
        )));
    }
    Ok((link, lib))
}

/// The `library` and published `component` params: (link, library, the component's snapshot id).
fn component_arg(s: &mut Session, cmd: &str, p: &Value) -> Result<(LibraryLink, Arc<PublishedLibrary>, NodeId)> {
    let (link, lib) = library(s, cmd, p)?;
    let v = get(p, "component").ok_or_else(|| bad(cmd, "`component` (id or name) required"))?;
    let m = &lib.manifest;
    let offered = |id: NodeId| asset_root(&lib.doc, id).and_then(|r| m.component(r)).is_some_and(|a| a.published);
    let by_name = || v.as_str().and_then(|t| m.components.iter().find(|a| a.published && a.name == t)).map(|a| a.id);
    let key = id_of(v).filter(|i| offered(*i)).or_else(by_name).ok_or_else(|| bad(cmd, format!("\"{}\" publishes no component {v}", link.name)))?;
    Ok((link, lib, key))
}

/// The `library` and a published variable named by `param` (id, else name): (library, the
/// variable's id in the library).
fn variable_arg(s: &mut Session, cmd: &str, p: &Value, param: &str) -> Result<(Arc<PublishedLibrary>, VariableId)> {
    let (link, lib) = library(s, cmd, p)?;
    let key = req_string(cmd, p, param)?;
    let id = published_variables(&lib).find(|v| v.id == key).or_else(|| published_variables(&lib).find(|v| v.name == key)).map(|v| v.id.clone());
    let id = id.ok_or_else(|| bad(cmd, format!("\"{}\" publishes no variable `{key}`", link.name)))?;
    Ok((lib, id))
}

/// Copy library variable `key` in (with what it aliases); its local id.
fn import_variable(s: &mut Session, lib: &PublishedLibrary, key: &str) -> Result<VariableId> {
    let map = import_variables(s.doc_mut()?, lib, &BTreeSet::from([key.to_string()]), &BTreeSet::new(), false);
    map.variables.get(key).cloned().ok_or_else(|| EngineError::Other("the variable didn't import".into()))
}

fn alias(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.aliasVariable";
    let own = req_string(cmd, p, "variable")?;
    let doc = s.doc()?;
    let kind = doc.variables.get(&own).filter(|v| !is_remote_variable(doc, &v.id)).map(|v| v.kind);
    let kind = kind.ok_or_else(|| bad(cmd, format!("no local variable `{own}`")))?;
    let (lib, key) = variable_arg(s, cmd, p, "alias")?;
    if lib.doc.variables.get(&key).is_some_and(|v| v.kind != kind) {
        return Err(bad(cmd, "the library variable has another type"));
    }
    let local = import_variable(s, &lib, &key)?;
    super::styles::var_set(s, &with(p, &["variable", "mode"], json!({"value": {"alias": local}})))?;
    Ok(json!({"variable": local}))
}

fn set_mode(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.setVariableMode";
    let (link, lib) = library(s, cmd, p)?;
    let key = req_string(cmd, p, "collection")?;
    let coll = published_collections(&lib)
        .find(|c| c.id == key)
        .or_else(|| published_collections(&lib).find(|c| c.name == key))
        .ok_or_else(|| bad(cmd, format!("\"{}\" publishes no variable collection `{key}`", link.name)))?;
    let m = req_string(cmd, p, "mode")?;
    let mode = coll.modes.iter().find(|x| x.id == m || x.name == m).map(|x| x.id.clone()).ok_or_else(|| bad(cmd, "no such mode"))?;
    let key = coll.id.clone();
    let map = import_variables(s.doc_mut()?, &lib, &BTreeSet::new(), &BTreeSet::from([key.clone()]), false);
    let local = map.collections.get(&key).cloned().ok_or_else(|| EngineError::Other("the collection didn't import".into()))?;
    super::styles::set_mode(s, &with(p, &["ids", "id"], json!({"collection": local, "mode": mode})))?;
    Ok(json!({"collection": local}))
}

fn extend(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.extendCollection";
    let (link, lib) = library(s, cmd, p)?;
    let key = req_string(cmd, p, "collection")?;
    let coll = published_collections(&lib)
        .find(|c| c.id == key)
        .or_else(|| published_collections(&lib).find(|c| c.name == key))
        .cloned()
        .ok_or_else(|| bad(cmd, format!("\"{}\" publishes no variable collection `{key}`", link.name)))?;
    let vars: BTreeSet<VariableId> = published_variables(&lib).filter(|v| v.collection == coll.id).map(|v| v.id.clone()).collect();
    let doc = s.doc_mut()?;
    let map = import_variables(doc, &lib, &vars, &BTreeSet::from([coll.id.clone()]), false);
    let parent = map.collections.get(&coll.id).cloned().ok_or_else(|| EngineError::Other("the collection didn't import".into()))?;
    let base = string(p, "name").map(|n| n.trim().chars().take(200).collect::<String>()).filter(|n| !n.is_empty());
    let base = base.unwrap_or_else(|| format!("{} (extended)", coll.name));
    let name = super::variables::free_collection_name(doc, &base);
    let id = doc.new_collection_id();
    doc.variables.collections.push(Collection { id: id.clone(), name, modes: Vec::new(), extends: Some(parent) });
    super::variables::sync_extensions(doc);
    Ok(json!({"id": id}))
}

/// What `p` asks `cmd` to publish of `doc` (`include`, else the default after `prev`; less
/// `exclude`) and its description.
fn publish_args(cmd: &str, doc: &Document, p: &Value, prev: Option<&LibraryManifest>) -> Result<(Selection, Option<String>)> {
    let all = publishable(doc);
    let coll_named = |c: &String, t: &str| doc.variables.collections.iter().any(|x| x.id == *c && x.name == t);
    let count = |s: &Selection| s.components.len() + s.styles.len() + s.collections.len();
    let pick = |key: &str| -> Result<Selection> {
        let mut sel = Selection::default();
        let Some(v) = get(p, key) else { return Ok(sel) };
        let Value::Array(items) = v else {
            return Err(bad(cmd, format!("`{key}` must be an array of component ids and style or variable collection ids or names")));
        };
        for item in items {
            let text = item.as_str().map(str::trim);
            let before = count(&sel);
            if let Some(t) = text.filter(|t| all.styles.iter().any(|x| x == t)) {
                sel.styles.push(t.to_string());
            } else if let Some(t) = text.filter(|t| all.collections.iter().any(|x| x == t)) {
                sel.collections.push(t.to_string());
            } else if let Some(i) = id_of(item).filter(|i| all.components.contains(i)) {
                sel.components.push(i);
            } else if let Some(t) = text {
                sel.components.extend(all.components.iter().filter(|i| doc.node(**i).is_some_and(|n| n.name == t)));
                sel.styles.extend(all.styles.iter().filter(|x| doc.style(x).is_some_and(|y| y.name == t)).cloned());
                sel.collections.extend(all.collections.iter().filter(|c| coll_named(c, t)).cloned());
            }
            if count(&sel) == before {
                return Err(bad(cmd, format!("{item} is not a local component, component set, style or variable collection of this file")));
            }
        }
        Ok(sel)
    };
    let mut sel = if get(p, "include").is_some() { pick("include")? } else { default_selection(doc, prev) };
    let x = pick("exclude")?;
    sel.components.retain(|c| !x.components.contains(c));
    sel.styles.retain(|s| !x.styles.contains(s));
    sel.collections.retain(|c| !x.collections.contains(c));
    let description = string(p, "description").map(|d| d.trim().chars().take(MAX_DESCRIPTION).collect());
    Ok((sel, description))
}

/// What a publish answers.
fn published_json(sel: &Selection, lib: &PublishedLibrary) -> Value {
    let m = &lib.manifest;
    json!({
        "id": m.id,
        "version": m.version,
        "components": sel.components.len(),
        "styles": sel.styles.len(),
        "collections": sel.collections.len(),
        "variables": m.variables.iter().filter(|v| v.published).count(),
    })
}

fn publish_cmd(s: &mut Session, p: &Value) -> Result<Value> {
    let doc = s.doc()?;
    let prev = doc.published.clone();
    let (sel, description) = publish_args("library.publish", doc, p, prev.as_ref().map(|l| &l.manifest))?;
    let lib = publish(doc, prev.as_deref(), &sel, description, s.ds()?.uid)?;
    let out = published_json(&sel, &lib);
    s.doc_mut()?.published = Some(Arc::new(lib));
    Ok(out)
}

/// A library request's answer that isn't the one expected.
fn unexpected(r: &LibraryReply) -> EngineError {
    EngineError::Other(format!("the server answered {r:?}"))
}

fn publish_to_server(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.publishToServer";
    let key = string(p, "key").map(|k| k.trim().to_string()).filter(|k| !k.is_empty());
    let server = string(p, "server").map(|v| v.trim().to_string()).filter(|v| !v.is_empty());
    let (doc, uid) = s.ds().map(|ds| (ds.doc.clone(), ds.uid))?;
    let mut kept = None;
    let link = match server {
        // The server's address with its key: the file is kept there first.
        Some(server) if key.is_some() || (server.contains("key=") && !server.contains("token=")) => {
            let opts = PublishOptions { server, key, name: doc.name.clone(), me: String::new(), doc: doc.clone(), share: false };
            let file = match s.net(NetRequest::Upload(opts))?.0 {
                NetReply::Upload(r) => r.map_err(|e| bad(cmd, e))?,
                _ => return Err(EngineError::Other("the server answered something else".into())),
            };
            let edit = file.edit.clone();
            kept = Some(file);
            edit
        }
        Some(link) => link,
        None => s.server_link().ok_or_else(|| {
            bad(cmd, "give `server` (an edit link of this file on a server, or the server's address with its key), or publish this file to a server first (Share ▸ Publish to server…)")
        })?,
    };
    // The server's version is the one to follow (others may have published since).
    let current = match s.library_request(&link, LibraryReq::Fetch { have: None, usage: None })? {
        LibraryReply::Library { archive, .. } => Some(read_archive(&archive).map_err(EngineError::Other)?),
        LibraryReply::Empty => None,
        other => return Err(unexpected(&other)),
    };
    let prev = current.as_ref().or(doc.published.as_deref());
    let (sel, description) = publish_args(cmd, &doc, p, prev.map(|l| &l.manifest))?;
    let lib = match (publish(&doc, prev, &sel, description, uid), &doc.published) {
        (Ok(lib), _) => lib,
        // This file's library as last published here, not on the server yet: as it is.
        (Err(_), Some(own)) if current.is_none() && !sel.is_empty() => (**own).clone(),
        (Err(e), _) => return Err(e),
    };
    let lib = match s.library_exchange(&link, LibraryReq::Publish { archive: archive(&lib)? })? {
        // Run again in the background: what the server keeps is what went out then (a new copy
        // differs at least in its time).
        (LibraryReply::Published { .. }, Some(LibraryReq::Publish { archive })) => read_archive(&archive).map_err(EngineError::Other)?,
        (LibraryReply::Published { .. }, _) => lib,
        (other, _) => return Err(unexpected(&other)),
    };
    let mut out = published_json(&sel, &lib);
    s.libraries.insert(&link, Ok(Arc::new(lib)));
    if let Some(f) = kept {
        out["file"] = json!(f.file);
        out["edit"] = json!(f.edit);
        out["view"] = json!(f.view);
    }
    Ok(out)
}

fn usage_cmd(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.usage";
    let link = match string(p, "library") {
        Some(key) => {
            let l = find_link(s.doc()?, &key).ok_or_else(|| bad(cmd, format!("no enabled library `{key}`")))?;
            if !is_server_link(&l.path) {
                return Err(bad(cmd, format!("\"{}\" is a library file, not a team library: only a server knows which files use it", l.name)));
            }
            l.path.clone()
        }
        None => s.server_link().ok_or_else(|| bad(cmd, "name an enabled team library, or open this file from its server"))?,
    };
    let lib = s.load_library(&link)?;
    let files = match s.library_request(&link, LibraryReq::Usage)? {
        LibraryReply::Usage(f) => f,
        other => return Err(unexpected(&other)),
    };
    let m = &lib.manifest;
    // Component → (instances, files using it).
    let mut per: std::collections::BTreeMap<NodeId, (u64, u64)> = std::collections::BTreeMap::new();
    let mut rows = Vec::new();
    for f in &files {
        let mut n = 0u64;
        for (c, k) in &f.usage.components {
            let e = per.entry(*c).or_default();
            e.0 += u64::from(*k);
            e.1 += 1;
            n += u64::from(*k);
        }
        rows.push(json!({"name": f.usage.file, "updated": f.updated, "instances": n}));
    }
    let mut comps: Vec<(NodeId, u64, u64)> = per.into_iter().map(|(c, (n, f))| (c, n, f)).collect();
    comps.sort_by(|a, b| b.1.cmp(&a.1).then(a.0.cmp(&b.0)));
    let components: Vec<Value> =
        comps.iter().map(|(c, n, f)| json!({"id": c, "name": m.component(*c).map(|a| a.name.clone()), "instances": n, "files": f})).collect();
    Ok(json!({
        "id": m.id,
        "name": m.name,
        "instances": comps.iter().map(|c| c.1).sum::<u64>(),
        "files": rows,
        "components": components,
    }))
}

fn swap_cmd(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.swap";
    let from = req_string(cmd, p, "from")?;
    let from = find_link(s.doc()?, &from).map(|l| l.id.clone()).ok_or_else(|| bad(cmd, format!("no enabled library `{from}`")))?;
    let to = req_string(cmd, p, "to")?;
    let (link, lib) = library(s, cmd, &json!({"library": to}))?;
    if link.id == from {
        return Err(bad(cmd, "`from` and `to` are the same library"));
    }
    let r = crate::library_swap::swap_library(s.doc_mut()?, &from, &lib)?;
    Ok(json!({"components": r.components, "styles": r.styles, "variables": r.variables, "unmatched": r.unmatched, "removed": r.removed}))
}

fn assets_json(lib: &PublishedLibrary) -> Value {
    let m = &lib.manifest;
    let modes = |c: &str| lib.doc.variables.collection(c).map(|c| c.modes.iter().map(|x| json!({"id": x.id, "name": x.name})).collect::<Vec<_>>());
    json!({
        "components": m.components.iter().filter(|a| a.published).map(|a| json!({"id": a.id, "name": a.name, "set": a.set, "version": a.version})).collect::<Vec<_>>(),
        "styles": m.styles.iter().filter(|x| x.published).map(|x| json!({"id": x.id, "name": x.name, "type": x.kind, "version": x.version})).collect::<Vec<_>>(),
        "collections": m.collections.iter().filter(|x| x.published).map(|x| json!({"id": x.id, "name": x.name, "modes": modes(&x.id), "version": x.version})).collect::<Vec<_>>(),
        "variables": m.variables.iter().filter(|x| x.published).map(|x| json!({"id": x.id, "name": x.name, "type": x.kind, "collection": x.collection, "version": x.version})).collect::<Vec<_>>(),
    })
}

fn list(s: &mut Session, p: &Value) -> Result<Value> {
    let with_assets = boolean(p, "assets").unwrap_or(false);
    let links = s.doc()?.libraries.enabled.clone();
    let mut out = Vec::new();
    for l in links {
        let mut e = json!({"id": l.id, "name": l.name, "path": l.path, "server": is_server_link(&l.path), "seenVersion": l.version});
        match s.fetch_library(&l.path, true) {
            Ok(lib) if lib.manifest.id == l.id => {
                e["version"] = json!(lib.manifest.version);
                e["description"] = json!(lib.manifest.description);
                e["updates"] = json!(pending(s.doc()?, &lib).count());
                if with_assets && let (Value::Object(e), Value::Object(a)) = (&mut e, assets_json(&lib)) {
                    e.extend(a);
                }
            }
            Ok(lib) => e["error"] = json!(format!("the file now holds another library (\"{}\")", lib.manifest.name)),
            Err(err) => e["error"] = json!(err.to_string()),
        }
        out.push(e);
    }
    let doc = s.doc()?;
    let published = doc.published.as_ref().map(|lib| {
        let m = &lib.manifest;
        let mut v = json!({"id": m.id, "name": m.name, "version": m.version, "description": m.description, "time": m.time,
            "components": m.components.iter().filter(|a| a.published).count(), "styles": m.styles.iter().filter(|x| x.published).count(),
            "collections": m.collections.iter().filter(|x| x.published).count(), "variables": m.variables.iter().filter(|x| x.published).count()});
        if with_assets {
            v["assets"] = assets_json(lib);
        }
        v
    });
    let mut res = json!({"libraries": out, "published": published});
    if with_assets {
        let (def, all) = (default_selection(doc, doc.published.as_ref().map(|l| &l.manifest)), publishable(doc));
        res["publishable"] = json!({
            "components": all.components.iter().filter_map(|c| doc.node(*c).map(|n| json!({"id": c, "name": n.name, "selected": def.components.contains(c)}))).collect::<Vec<_>>(),
            "styles": all.styles.iter().filter_map(|x| doc.style(x).map(|st| json!({"id": st.id, "name": st.name, "selected": def.styles.contains(x)}))).collect::<Vec<_>>(),
            "collections": all.collections.iter().filter_map(|x| doc.variables.collection(x).map(|c| json!({"id": c.id, "name": c.name, "selected": def.collections.contains(x)}))).collect::<Vec<_>>(),
        });
    }
    Ok(res)
}

fn add(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.add";
    let raw = req_string(cmd, p, "path")?;
    let path = if is_server_link(&raw) { raw.trim().to_string() } else { absolute_path(raw.trim()) };
    let lib = s.load_library(&path)?;
    let m = &lib.manifest;
    let doc = s.doc()?;
    if doc.published.as_ref().is_some_and(|me| me.manifest.id == m.id) {
        return Err(EngineError::Disabled(cmd.into(), format!("this file is the library \"{}\"", m.name)));
    }
    let unchanged = doc.libraries.link(&m.id).is_some_and(|l| l.path == path && l.name == m.name);
    if !unchanged {
        let libs = s.doc_mut()?.libraries_mut();
        match libs.enabled.iter_mut().find(|l| l.id == m.id) {
            // The same library from another place (the file moved): follow it.
            Some(l) => {
                l.path = path.clone();
                l.name = m.name.clone();
            }
            None => libs.enabled.push(LibraryLink { id: m.id.clone(), name: m.name.clone(), path: path.clone(), version: m.version }),
        }
    }
    let mut out = assets_json(&lib);
    out["id"] = json!(m.id);
    out["name"] = json!(m.name);
    out["version"] = json!(m.version);
    out["path"] = json!(path);
    Ok(out)
}

fn remove(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.remove";
    let key = req_string(cmd, p, "id")?;
    let id = find_link(s.doc()?, &key).map(|l| l.id.clone()).ok_or_else(|| bad(cmd, format!("no enabled library `{key}`")))?;
    let doc = s.doc_mut()?;
    doc.libraries_mut().enabled.retain(|l| l.id != id);
    prune(doc, &id)?;
    Ok(json!({"removed": id}))
}

fn updates(s: &mut Session, _p: &Value) -> Result<Value> {
    let links = s.doc()?.libraries.enabled.clone();
    let (mut out, mut errors, mut count) = (Vec::new(), Vec::new(), 0);
    for l in links {
        let lib = match s.fetch_library(&l.path, true) {
            Ok(lib) if lib.manifest.id == l.id => lib,
            Ok(_) => {
                errors.push(json!({"id": l.id, "name": l.name, "error": "the file now holds another library"}));
                continue;
            }
            Err(e) => {
                errors.push(json!({"id": l.id, "name": l.name, "error": e.to_string()}));
                continue;
            }
        };
        let p = pending(s.doc()?, &lib);
        if p.is_empty() {
            continue;
        }
        count += p.count();
        let m = &lib.manifest;
        let name = |r: &ImportedComponent| m.component(r.key).map(|a| a.name.clone()).unwrap_or_default();
        let rows = |list: &[ImportedRecord], name: &dyn Fn(&str) -> Option<String>| {
            // A variable new to an extended collection has no copy yet: no `id`.
            list.iter().map(|r| json!({"id": (!r.local.is_empty()).then_some(&r.local), "key": r.key, "name": name(&r.key)})).collect::<Vec<_>>()
        };
        out.push(json!({
            "id": l.id,
            "name": m.name,
            "version": m.version,
            "components": p.components.iter().map(|r| json!({"id": r.root, "key": r.key, "name": name(r)})).collect::<Vec<_>>(),
            "styles": rows(&p.styles, &|k| m.style(k).map(|x| x.name.clone())),
            "collections": rows(&p.collections, &|k| m.collection(k).map(|x| x.name.clone())),
            "variables": rows(&p.variables, &|k| m.variable(k).map(|x| x.name.clone())),
        }));
    }
    Ok(json!({"count": count, "libraries": out, "errors": errors}))
}

fn accept(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.acceptUpdates";
    let named: Option<Vec<String>> = match get(p, "ids") {
        Some(Value::Array(a)) => Some(a.iter().filter_map(|v| v.as_str().map(str::to_string)).collect()),
        Some(Value::String(one)) => Some(vec![one.clone()]),
        Some(_) => return Err(bad(cmd, "`ids` must be an array of library ids")),
        None => None,
    };
    let links: Vec<LibraryLink> = match &named {
        Some(keys) => keys
            .iter()
            .map(|k| find_link(s.doc()?, k).cloned().ok_or_else(|| bad(cmd, format!("no enabled library `{k}`"))))
            .collect::<Result<_>>()?,
        None => s.doc()?.libraries.enabled.clone(),
    };
    let (mut done, mut skipped) = (Pending::default(), Vec::new());
    for l in links {
        let lib = match library(s, cmd, &json!({"library": l.id})) {
            Ok((_, lib)) => lib,
            Err(e) if named.is_none() => {
                skipped.push(json!({"id": l.id, "name": l.name, "error": e.to_string()}));
                continue;
            }
            Err(e) => return Err(e),
        };
        let p = accept_updates(s.doc_mut()?, &lib)?;
        done.components.extend(p.components);
        done.styles.extend(p.styles);
        done.collections.extend(p.collections);
        done.variables.extend(p.variables);
    }
    Ok(json!({
        "components": done.components.len(),
        "styles": done.styles.len(),
        "collections": done.collections.len(),
        "variables": done.variables.len(),
        "skipped": skipped,
    }))
}

fn place(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.place";
    let (_, lib, key) = component_arg(s, cmd, p)?;
    let (cx, cy) = s.ds().map(|d| (d.view.cx, d.view.cy))?;
    let (x, y) = (num(p, "x").unwrap_or(cx), num(p, "y").unwrap_or(cy));
    let map = import(s.doc_mut()?, &lib, &[key], false)?;
    let local = map.get(&key).copied().ok_or_else(|| EngineError::Other("the component didn't import".into()))?;
    let mut out = super::component::place(s, &json!({"component": local, "x": x, "y": y}))?;
    out["component"] = json!(local);
    Ok(out)
}

fn apply_style(s: &mut Session, p: &Value) -> Result<Value> {
    let cmd = "library.applyStyle";
    let (link, lib) = library(s, cmd, p)?;
    let key = req_string(cmd, p, "style")?;
    let m = &lib.manifest;
    let style = m
        .styles
        .iter()
        .filter(|x| x.published)
        .find(|x| x.id == key)
        .or_else(|| m.styles.iter().filter(|x| x.published).find(|x| x.name == key))
        .map(|x| x.id.clone())
        .ok_or_else(|| bad(cmd, format!("\"{}\" publishes no style `{key}`", link.name)))?;
    let local = import_styles(s.doc_mut()?, &lib, &[style].into_iter().collect(), false)
        .into_values()
        .next()
        .ok_or_else(|| EngineError::Other("the style didn't import".into()))?;
    super::styles::apply(s, &with(p, &["ids", "id", "target"], json!({"style": local})))?;
    Ok(json!({"style": local}))
}