import { newId } from '../ids';
import {
  ANIMATION_ROOT_TYPES,
  blends,
  findTrack,
  hasKey,
  isKeyInterpolation,
  type KeyRef,
  normalizeKeys,
  targetAssetOf,
  targetDefs,
  trackDef,
  trackValueAt,
} from '../model/animation';
import type { AnimationAsset, AnimationKey, AnimationTrack, KeyInterpolation } from '../model/Asset';
import { curveLookup } from '../model/curve';
import { findAsset, type Project } from '../model/Project';
import type { PropertyValue } from '../model/Properties';
import { coerceValue } from '../properties/PropertySchema';
import { type Command, CommandError } from './Command';
import { requireAsset } from './require';

function requireAnimation(project: Project, assetId: string): AnimationAsset {
  const asset = requireAsset(project, assetId);
  if (asset.type !== 'animation') throw new CommandError(`${asset.name} is not an animation`);
  return asset;
}

function requireTrack(asset: AnimationAsset, trackId: string): AnimationTrack {
  const track = findTrack(asset, trackId);
  if (!track) throw new CommandError(`${asset.name} has no such row`);
  return track;
}

function requireKey(asset: AnimationAsset, ref: KeyRef): { track: AnimationTrack; key: AnimationKey } {
  const track = requireTrack(asset, ref.trackId);
  const key = track.keys.find((k) => k.frame === ref.frame);
  if (!key) throw new CommandError(`No key on frame ${ref.frame}`);
  return { track, key };
}

function requireFrame(frame: number, message: string): void {
  if (!Number.isInteger(frame) || frame < 0) throw new CommandError(message);
}

/** `Remove key`, `Remove 3 keys` – how a key command names itself. */
function keysLabel(verb: string, count: number): string {
  return count === 1 ? `${verb} key` : `${verb} ${count} keys`;
}

/** The kind of `property` on the object `target` names, refusing what cannot be animated there. */
function requireAnimatable(
  project: Project,
  asset: AnimationAsset,
  target: string,
  property: string,
): string {
  if (!findAsset(project, asset.root)) throw new CommandError(`${asset.name} has nothing to animate yet`);
  const defs = targetDefs(project, asset, target);
  if (!defs) throw new CommandError('That object is not part of the animated asset');
  const kind = defs.find((d) => d.key === property)?.kind;
  if (!kind)
    throw new CommandError(
      `${targetAssetOf(project, asset, target)?.name} has no property ${property} to animate`,
    );
  return kind;
}

function requireUnique(asset: AnimationAsset, target: string, property: string, except = ''): void {
  if (asset.tracks.some((t) => t.id !== except && t.target === target && t.property === property))
    throw new CommandError('That property already has a row');
}

/**
 * Every edit of a timeline keeps the rows as they were and puts them back on undo – the rows of
 * one asset are small, and a key move that swallows another key is exactly undone this way.
 */
abstract class TimelineCommand implements Command {
  abstract readonly label: string;
  private before: AnimationTrack[] = [];
  private rootBefore = '';

  constructor(protected readonly assetId: string) {}

  execute(project: Project): void {
    const asset = requireAnimation(project, this.assetId);
    this.before = structuredClone(asset.tracks);
    this.rootBefore = asset.root;
    try {
      this.apply(project, asset);
    } catch (error) {
      asset.tracks = this.before;
      asset.root = this.rootBefore;
      throw error;
    }
  }

  undo(project: Project): void {
    const asset = requireAnimation(project, this.assetId);
    asset.tracks = structuredClone(this.before);
    asset.root = this.rootBefore;
  }

  protected abstract apply(project: Project, asset: AnimationAsset): void;
}

/** The rows stay: a row whose object the new root lacks reads as missing and keeps its keys. */
export class SetAnimationRootCommand extends TimelineCommand {
  readonly label = 'Set animated asset';

  constructor(
    assetId: string,
    private readonly rootId: string,
  ) {
    super(assetId);
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    if (this.rootId !== '') {
      const root = requireAsset(project, this.rootId);
      if (!ANIMATION_ROOT_TYPES.includes(root.type))
        throw new CommandError(`A ${root.type} cannot be animated`);
    }
    asset.root = this.rootId;
  }
}

export class AddAnimationTrackCommand extends TimelineCommand {
  readonly label = 'Add row';
  readonly trackId = newId();

  constructor(
    assetId: string,
    private readonly target: string,
    private readonly property: string,
  ) {
    super(assetId);
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    requireAnimatable(project, asset, this.target, this.property);
    requireUnique(asset, this.target, this.property);
    asset.tracks.push({ id: this.trackId, target: this.target, property: this.property, keys: [] });
  }
}

export class RemoveAnimationTracksCommand extends TimelineCommand {
  readonly label: string;

  constructor(
    assetId: string,
    private readonly trackIds: readonly string[],
  ) {
    super(assetId);
    this.label = trackIds.length === 1 ? 'Remove row' : `Remove ${trackIds.length} rows`;
  }

  protected apply(_project: Project, asset: AnimationAsset): void {
    for (const id of this.trackIds) requireTrack(asset, id);
    asset.tracks = asset.tracks.filter((t) => !this.trackIds.includes(t.id));
  }
}

/**
 * Aims a row somewhere else and keeps its keys – only at a property of the same kind, since a
 * color key would mean nothing on a switch. A row aiming at something gone may go anywhere.
 */
export class RetargetAnimationTrackCommand extends TimelineCommand {
  readonly label = 'Change row';

  constructor(
    assetId: string,
    private readonly trackId: string,
    private readonly target: string,
    private readonly property: string,
  ) {
    super(assetId);
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    const track = requireTrack(asset, this.trackId);
    const kind = requireAnimatable(project, asset, this.target, this.property);
    const was = trackDef(project, asset, track)?.kind;
    if (was !== undefined && was !== kind) throw new CommandError(`A ${was} row cannot become a ${kind} row`);
    requireUnique(asset, this.target, this.property, track.id);
    track.target = this.target;
    track.property = this.property;
    if (kind !== 'number') delete track.relative;
  }
}

/** Only a number can be relative: an offset of a color or a picture means nothing. */
export class SetTrackRelativeCommand extends TimelineCommand {
  readonly label: string;

  constructor(
    assetId: string,
    private readonly trackId: string,
    private readonly relative: boolean,
  ) {
    super(assetId);
    this.label = relative ? 'Make row relative' : 'Make row absolute';
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    const track = requireTrack(asset, this.trackId);
    if (this.relative) {
      if (requireAnimatable(project, asset, track.target, track.property) !== 'number')
        throw new CommandError('Only a number row can be relative');
      track.relative = true;
    } else delete track.relative;
  }
}

/**
 * Sets the key at `frame`, replacing the value of one already there but keeping its interpolation.
 * Without a value it takes the value the row has at that frame – what a double click in the timeline
 * means – and on an empty row the property's default, which for a relative row is no offset at all.
 */
export class SetAnimationKeyCommand extends TimelineCommand {
  readonly label = 'Set key';

  constructor(
    assetId: string,
    private readonly trackId: string,
    private readonly frame: number,
    private readonly value?: PropertyValue,
  ) {
    super(assetId);
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    const track = requireTrack(asset, this.trackId);
    requireFrame(this.frame, 'A key sits on a whole frame from 0');
    const def = trackDef(project, asset, track);
    if (!def) throw new CommandError('The row aims at something that is gone');
    const current = trackValueAt(track.keys, def.kind, this.frame, false, curveLookup(project));
    const raw = this.value ?? current ?? (track.relative ? 0 : def.default);
    const key: AnimationKey = { frame: this.frame, value: coerceValue(def, raw) };
    const interpolation = track.keys.find((k) => k.frame === this.frame)?.interpolation;
    if (interpolation) key.interpolation = interpolation;
    track.keys = normalizeKeys([...track.keys, key]);
  }
}

/**
 * Keys a number row straight from one value to another (#407): both keys set, the first one linear,
 * the keys between them gone – what a driven video needs to run at 1× without a bend.
 */
export class KeyStraightRunCommand extends TimelineCommand {
  readonly label = 'Key video at 1×';
  /** How many keys between the two were taken out. */
  removed = 0;

  constructor(
    assetId: string,
    private readonly trackId: string,
    private readonly from: AnimationKey,
    private readonly to: AnimationKey,
  ) {
    super(assetId);
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    const track = requireTrack(asset, this.trackId);
    requireFrame(this.from.frame, 'A key sits on a whole frame from 0');
    requireFrame(this.to.frame, 'A key sits on a whole frame from 0');
    if (this.to.frame <= this.from.frame) throw new CommandError('The run has to end after it starts');
    const def = trackDef(project, asset, track);
    if (def?.kind !== 'number') throw new CommandError('Only a number row can run straight');
    const kept = track.keys.filter((k) => k.frame < this.from.frame || k.frame > this.to.frame);
    const end = track.keys.find((k) => k.frame === this.to.frame);
    this.removed = track.keys.filter((k) => k.frame > this.from.frame && k.frame < this.to.frame).length;
    const last: AnimationKey = { frame: this.to.frame, value: coerceValue(def, this.to.value) };
    if (end?.interpolation) last.interpolation = end.interpolation;
    track.keys = normalizeKeys([
      ...kept,
      { frame: this.from.frame, value: coerceValue(def, this.from.value) },
      last,
    ]);
  }
}

/**
 * Sets how each key blends into the next one. `linear` is stored as no field at all. A key on a row
 * that cannot blend is left as it is – it jumps whatever it says – and only such keys is refused.
 */
export class SetKeyInterpolationCommand extends TimelineCommand {
  readonly label: string;

  constructor(
    assetId: string,
    private readonly keys: readonly KeyRef[],
    private readonly interpolation: KeyInterpolation,
  ) {
    super(assetId);
    this.label = keys.length === 1 ? 'Set easing' : `Set easing of ${keys.length} keys`;
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    if (!isKeyInterpolation(this.interpolation)) throw new CommandError('No such easing');
    let changed = 0;
    for (const ref of this.keys) {
      const { track, key } = requireKey(asset, ref);
      const kind = trackDef(project, asset, track)?.kind;
      if (kind !== undefined && !blends(kind)) continue;
      if (this.interpolation === 'linear') delete key.interpolation;
      else key.interpolation = this.interpolation;
      changed += 1;
    }
    if (changed === 0) throw new CommandError('Only a number or color key can ease');
  }
}

export class RemoveAnimationKeysCommand extends TimelineCommand {
  readonly label: string;

  constructor(
    assetId: string,
    private readonly keys: readonly KeyRef[],
  ) {
    super(assetId);
    this.label = keysLabel('Remove', keys.length);
  }

  protected apply(_project: Project, asset: AnimationAsset): void {
    if (this.keys.length === 0) throw new CommandError('No keys to remove');
    for (const ref of this.keys) {
      const { track, key } = requireKey(asset, ref);
      track.keys.splice(track.keys.indexOf(key), 1);
    }
  }
}

/**
 * Shifts the keys by `delta` frames together; one landing on a key that stays behind replaces it.
 * With `copy` the originals stay where they were and the copies travel – Ctrl+drag (#102).
 */
export class MoveAnimationKeysCommand extends TimelineCommand {
  readonly label: string;

  constructor(
    assetId: string,
    private readonly keys: readonly KeyRef[],
    private readonly delta: number,
    private readonly copy = false,
  ) {
    super(assetId);
    this.label = keysLabel(copy ? 'Duplicate' : 'Move', keys.length);
  }

  protected apply(_project: Project, asset: AnimationAsset): void {
    if (!Number.isInteger(this.delta)) throw new CommandError('Keys move by whole frames');
    if (this.copy && this.delta === 0) throw new CommandError('A duplicate has to land somewhere else');
    const byTrack = new Map<string, Set<number>>();
    for (const ref of this.keys) {
      requireKey(asset, ref);
      if (ref.frame + this.delta < 0) throw new CommandError('A key cannot move before frame 0');
      byTrack.set(ref.trackId, (byTrack.get(ref.trackId) ?? new Set()).add(ref.frame));
    }
    for (const [trackId, frames] of byTrack) {
      const track = requireTrack(asset, trackId);
      const staying = this.copy ? track.keys : track.keys.filter((k) => !frames.has(k.frame));
      const moved = track.keys
        .filter((k) => frames.has(k.frame))
        .map((k) => ({ ...k, frame: k.frame + this.delta }));
      // Later wins in `normalizeKeys`, so the moved keys go last.
      track.keys = normalizeKeys([...staying, ...moved]);
    }
  }
}

/** One row of copied keys: where it came from, its kind, and the keys counted from the first copied frame. */
export interface ClipboardRow {
  trackId: string;
  target: string;
  property: string;
  /** Unknown when the row aimed at something gone – such keys only go back onto that very row. */
  kind: string | null;
  keys: { offset: number; value: PropertyValue; interpolation?: KeyInterpolation }[];
}

/** What Ctrl+C on picked keys holds (#102). Frames are relative: the earliest copied key is offset 0. */
export interface KeyClipboard {
  assetId: string;
  rows: ClipboardRow[];
}

export function clipboardKeyCount(clipboard: KeyClipboard): number {
  return clipboard.rows.reduce((n, r) => n + r.keys.length, 0);
}

/** The picked keys as a clipboard, or null when none of them exists. */
export function copyAnimationKeys(
  project: Project,
  asset: AnimationAsset,
  refs: readonly KeyRef[],
): KeyClipboard | null {
  const picked = asset.tracks
    .map((track) => ({
      track,
      keys: track.keys.filter((k) => hasKey(refs, { trackId: track.id, frame: k.frame })),
    }))
    .filter((p) => p.keys.length > 0);
  if (picked.length === 0) return null;
  const first = Math.min(...picked.flatMap((p) => p.keys.map((k) => k.frame)));
  return {
    assetId: asset.id,
    rows: picked.map(({ track, keys }) => ({
      trackId: track.id,
      target: track.target,
      property: track.property,
      kind: trackDef(project, asset, track)?.kind ?? null,
      keys: keys.map((k) => ({
        offset: k.frame - first,
        value: structuredClone(k.value),
        ...(k.interpolation ? { interpolation: k.interpolation } : {}),
      })),
    })),
  };
}

/**
 * Pastes a clipboard with its first key on `frame`. Keys of one row go onto `intoTrackId` when given
 * – the row picked in the timeline – as long as it has the same kind. Otherwise every row finds its
 * own: the same row in the animation it came from, the row animating the same property elsewhere.
 * Rows that find none are left out and counted in `skipped`; a pasted key replaces one already there.
 */
export class PasteAnimationKeysCommand extends TimelineCommand {
  readonly label: string;
  /** The keys as they landed, for the timeline to pick. */
  pasted: KeyRef[] = [];
  skipped = 0;

  constructor(
    assetId: string,
    private readonly clipboard: KeyClipboard,
    private readonly frame: number,
    private readonly intoTrackId = '',
  ) {
    super(assetId);
    this.label = keysLabel('Paste', clipboardKeyCount(clipboard));
  }

  protected apply(project: Project, asset: AnimationAsset): void {
    requireFrame(this.frame, 'Keys paste onto a whole frame from 0');
    this.pasted = [];
    this.skipped = 0;
    const single = this.clipboard.rows.length === 1 && this.intoTrackId !== '';
    for (const row of this.clipboard.rows) {
      const track = single ? requireTrack(asset, this.intoTrackId) : this.matchingTrack(asset, row);
      if (!track) {
        this.skipped += 1;
        continue;
      }
      const def = trackDef(project, asset, track);
      if (row.kind === null ? track.id !== row.trackId : def?.kind !== row.kind) {
        if (single)
          throw new CommandError(
            def
              ? `${row.kind ?? 'These'} keys cannot go on a ${def.kind} row`
              : 'The row aims at something that is gone',
          );
        this.skipped += 1;
        continue;
      }
      const keys = row.keys.map((k) => {
        const key: AnimationKey = {
          frame: this.frame + k.offset,
          value: def ? coerceValue(def, k.value) : structuredClone(k.value),
        };
        if (k.interpolation && (!def || blends(def.kind))) key.interpolation = k.interpolation;
        return key;
      });
      track.keys = normalizeKeys([...track.keys, ...keys]);
      this.pasted.push(...keys.map((k) => ({ trackId: track.id, frame: k.frame })));
    }
    if (this.pasted.length === 0) throw new CommandError('None of the copied rows is in this animation');
  }

  private matchingTrack(asset: AnimationAsset, row: ClipboardRow): AnimationTrack | undefined {
    return asset.id === this.clipboard.assetId
      ? findTrack(asset, row.trackId)
      : asset.tracks.find((t) => t.target === row.target && t.property === row.property);
  }
}

/**
 * Where a key on `frame` ends up when `count` frames are inserted at `at` (count > 0) or removed from
 * it (count < 0): keys from `at` on move, and removing drops the keys in the removed span (null).
 */
export function shiftedFrame(frame: number, at: number, count: number): number | null {
  if (frame < at) return frame;
  if (count < 0 && frame < at - count) return null;
  return frame + count;
}

/**
 * Inserts (`count` > 0) or removes (`count` < 0) frames at `at`, over every row – the way to make an
 * animation longer or shorter in the middle (#102). A step that would change nothing is refused.
 */
export class ShiftAnimationFramesCommand extends TimelineCommand {
  readonly label: string;

  constructor(
    assetId: string,
    private readonly at: number,
    private readonly count: number,
  ) {
    super(assetId);
    const frames = Math.abs(count) === 1 ? 'frame' : `${Math.abs(count)} frames`;
    this.label = count > 0 ? `Insert ${frames}` : `Remove ${frames}`;
  }

  protected apply(_project: Project, asset: AnimationAsset): void {
    requireFrame(this.at, 'Frames are inserted at a whole frame from 0');
    if (!Number.isInteger(this.count) || this.count === 0)
      throw new CommandError('Give a whole number of frames');
    let touched = 0;
    for (const track of asset.tracks) {
      const keys: AnimationKey[] = [];
      for (const key of track.keys) {
        const frame = shiftedFrame(key.frame, this.at, this.count);
        if (frame !== key.frame) touched += 1;
        if (frame !== null) keys.push({ ...key, frame });
      }
      track.keys = keys;
    }
    if (touched === 0) throw new CommandError(`No keys from frame ${this.at} on`);
  }
}