import type { CanvasRecord, Change, Data, Document, ElementRecord, Id, Json, Point, Registry, Target } from './types.ts';
import { copySlots } from './copy-paths.ts';
import { ancestors, commonCanvas, targetElement, validateDocumentSteps } from './document.ts';
import { connectionPathValid } from './features.ts';
import { canvasTransform, convertPath, toLocal, toWorld } from './coordinates.ts';
import { clone, fault, freeze } from './values.ts';

export type DuplicatePlan = { readonly version: 1; readonly roots: readonly Id[]; readonly elementIds: Readonly<Record<Id, Id>>; readonly canvasIds: Readonly<Record<Id, Id>>; readonly changes: readonly Change[] };
export type DuplicateOptions = { readonly createId: () => Id; readonly worldOffset?: Point; readonly mapping?: { readonly elements: Readonly<Record<Id, Id>>; readonly canvases: Readonly<Record<Id, Id>> } };

export function remapCopyData(element: ElementRecord, registry: Registry, elements: ReadonlyMap<Id, Id>, canvases: ReadonlyMap<Id, Id>, document: Document): Data {
  const definition = registry.components.get(element.componentId), schema = definition?.copy;
  if (registry.resolve(element) !== 'known' || !schema) throw fault('copy_schema_unavailable', [element.id]);
  const data = clone(element.data) as Record<string, Json>;
  for (const ref of schema.references) {
    for (const slot of copySlots(data, ref.path)) {
      if (slot.parent[slot.key] === null) continue;
      const mapped = (value: Json): Json => {
        if (typeof value !== 'string' || !value) throw fault('invalid_copy_reference', [element.id]);
        const map = ref.target === 'element' ? elements : canvases, known = ref.target === 'element' ? document.elements : document.canvases;
        if (map.has(value)) return map.get(value)!;
        if (ref.external !== 'preserve' || !known.has(value)) throw fault('copy_external_reference', [element.id, value]);
        return value;
      };
      const value = slot.parent[slot.key];
      if (ref.many && !Array.isArray(value)) throw fault('invalid_copy_reference', [element.id]);
      slot.parent[slot.key] = ref.many ? (value as Json[]).map(mapped) : mapped(value);
    }
  }
  for (const path of schema.omit) for (const slot of copySlots(data, path)) { if (Array.isArray(slot.parent)) throw fault('invalid_copy_omit', [element.id]); delete slot.parent[slot.key]; }
  return data;
}

/** Pure, complete-snapshot planning. Runtime owns time slicing, durable source/mapping and partial progress. */
export function* planDuplicateSteps(document: Document, registry: Registry, selection: readonly Target[], options: DuplicateOptions): Generator<void, DuplicatePlan> {
  yield* validateDocumentSteps(document, registry);
  const offset = options.worldOffset ?? { x: 32, y: 32 };
  if (![offset.x, offset.y].every(Number.isFinite)) throw fault('invalid_copy_offset');
  const selected = new Set<Id>();
  for (const target of selection) { yield; selected.add(targetElement(document, target).id); }
  if (!selected.size) throw fault('empty_copy_selection');
  const childByEntry = new Map<Id, CanvasRecord>(), members = new Map<Id, ElementRecord[]>();
  for (const canvas of document.canvases.values()) { yield; if (canvas.parent) childByEntry.set(canvas.parent.entryElementId, canvas); }
  for (const element of document.elements.values()) { yield; const list = members.get(element.ownerCanvasId) ?? []; list.push(element); members.set(element.ownerCanvasId, list); }
  const roots: Id[] = [];
  for (const id of selected) { yield; if (!ancestors(document, document.elements.get(id)!.ownerCanvasId).some(canvas => { const parent = document.canvases.get(canvas)!.parent; return parent && selected.has(parent.entryElementId); })) roots.push(id); }
  const copied = new Set<Id>(), copiedCanvases = new Set<Id>(), order: ({ kind: 'element'; record: ElementRecord } | { kind: 'canvas'; record: CanvasRecord })[] = [];
  const work: typeof order = [];
  for (let index = roots.length - 1; index >= 0; index--) { yield; const record = document.elements.get(roots[index])!; if (record.structure === 'node') work.push({kind:'element',record}); }
  while (work.length) {
    yield;
    const item = work.pop()!;
    if (item.kind === 'canvas') {
      if (copiedCanvases.has(item.record.id)) continue;
      copiedCanvases.add(item.record.id); order.push(item);
      const list = members.get(item.record.id) ?? [];
      for (let index = list.length - 1; index >= 0; index--) { yield; const member = list[index]; if (member.structure === 'node') work.push({ kind: 'element', record: member }); }
    } else {
      if (copied.has(item.record.id)) continue;
      copied.add(item.record.id); order.push(item);
      const child = childByEntry.get(item.record.id); if (child) work.push({ kind: 'canvas', record: child });
    }
  }
  const edges: ElementRecord[] = [];
  for (const element of document.elements.values()) { yield; if (element.structure === 'connection' && (selected.has(element.id) || copiedCanvases.has(element.ownerCanvasId) || copied.has(element.target.elementId))) { edges.push(element); copied.add(element.id); } }
  const elementIds = new Map<Id, Id>(), canvasIds = new Map<Id, Id>(), used = new Set<Id>();
  for (const map of [document.elements, document.canvases, document.tombstones]) for (const id of map.keys()) { yield; used.add(id); }
  const allocate = (source: Id, kind: 'elements' | 'canvases') => {
    const supplied = options.mapping?.[kind];
    const id = supplied && Object.hasOwn(supplied, source) ? supplied[source] : options.createId();
    if (typeof id !== 'string' || !id || used.has(id)) throw fault('duplicate_identity', [id]);
    used.add(id); return id;
  };
  for (const id of copied) { yield; elementIds.set(id, allocate(id, 'elements')); }
  for (const id of copiedCanvases) { yield; canvasIds.set(id, allocate(id, 'canvases')); }
  if (options.mapping) for (const [mapping, scope] of [[options.mapping.elements,copied],[options.mapping.canvases,copiedCanvases]] as const) for (const id in mapping) { yield; if (Object.hasOwn(mapping,id) && !scope.has(id)) throw fault('copy_mapping_scope_mismatch'); }
  const changes: Change[] = [];
  for (const item of order) {
    yield;
    changes.push(duplicateTreeChange(document,registry,item.kind,item.record,elementIds,canvasIds,copiedCanvases,offset));
  }
  const nodeElements = new Map<Id, ElementRecord>(), nodeCanvases = new Map<Id, CanvasRecord>();
  for (const change of changes) { yield; if (change.kind === 'element' && change.after) nodeElements.set(change.id, change.after); else if (change.kind === 'canvas' && change.after) nodeCanvases.set(change.id, change.after); }
  const nodes: Document = { ...document, elements: overlay(document.elements, nodeElements), canvases: overlay(document.canvases, nodeCanvases) };
  for (const edge of edges) {
    yield;
    const change=duplicateEdgeChange(document,registry,edge,elementIds,canvasIds,nodes);
    changes.push(change);nodeElements.set(change.id,change.after!);
  }
  yield* validateDocumentSteps(nodes, registry);
  const elementMapping: Record<Id,Id> = {}, canvasMapping: Record<Id,Id> = {}, copiedRoots: Id[] = [];
  for (const [id, value] of elementIds) { yield; Object.defineProperty(elementMapping,id,{value,enumerable:true}); }
  for (const [id, value] of canvasIds) { yield; Object.defineProperty(canvasMapping,id,{value,enumerable:true}); }
  for (const id of roots) { yield; copiedRoots.push(elementIds.get(id)!); }
  for (const change of changes) { yield; freeze(change); }
  return Object.freeze({ version: 1, roots: Object.freeze(copiedRoots), elementIds: Object.freeze(elementMapping), canvasIds: Object.freeze(canvasMapping), changes: Object.freeze(changes) });
}

/** Shared deterministic emitters for synchronous and checkpointed planners. */
export function duplicateTreeChange(document:Document,registry:Registry,kind:'element'|'canvas',record:ElementRecord|CanvasRecord,elementIds:ReadonlyMap<Id,Id>,canvasIds:ReadonlyMap<Id,Id>,copiedCanvases:ReadonlySet<Id>,offset:Point):Exclude<Change,{kind:'field'}>{
    if (kind === 'canvas') {
      const canvas=record as CanvasRecord,parent=canvas.parent!;
      const after = { ...clone(canvas), id: canvasIds.get(canvas.id)!, parent: { ...parent, canvasId: canvasIds.get(parent.canvasId) ?? parent.canvasId, entryElementId: elementIds.get(parent.entryElementId)! } };
      return { kind: 'canvas', id: after.id, before: null, after };
    } else {
      const old = record as ElementRecord; if (old.structure !== 'node') throw fault('invalid_copy_node');
      let geometry = clone(old.geometry);
      if (!copiedCanvases.has(old.ownerCanvasId)) {
        const transform = canvasTransform(document, old.ownerCanvasId), zero = toLocal(transform, { x: 0, y: 0 }), shift = toLocal(transform, offset);
        geometry = { ...geometry, x: geometry.x + shift.x - zero.x, y: geometry.y + shift.y - zero.y };
      }
      const after = { ...clone(old), id: elementIds.get(old.id)!, incarnation: 1, ownerCanvasId: canvasIds.get(old.ownerCanvasId) ?? old.ownerCanvasId, data: remapCopyData(old, registry, elementIds, canvasIds, document), geometry };
      return { kind: 'element', id: after.id, before: null, after };
    }
}
export function duplicateEdgeChange(document:Document,registry:Registry,edge:ElementRecord,elementIds:ReadonlyMap<Id,Id>,canvasIds:ReadonlyMap<Id,Id>,nodes:Document):Extract<Change,{kind:'element'}>{
    if (edge.structure !== 'connection') throw fault('invalid_copy_endpoint');
    if (!connectionPathValid(edge.path)) throw fault('unsupported_copy_path', [edge.id]);
    const source = { ...edge.source, elementId: elementIds.get(edge.source.elementId) ?? edge.source.elementId }, target = { ...edge.target, elementId: elementIds.get(edge.target.elementId) ?? edge.target.elementId };
    const owner = commonCanvas(nodes, nodes.elements.get(source.elementId)!.ownerCanvasId, nodes.elements.get(target.elementId)!.ownerCanvasId), transform = canvasTransform(nodes, owner);
    let path = convertPath(edge.path, canvasTransform(document, edge.ownerCanvasId), transform);
    if (path && typeof path === 'object' && !Array.isArray(path) && Array.isArray(path.knots)) {
      const displacement = (beforeId: Id, afterId: Id) => {
        const a = document.elements.get(beforeId)!, b = nodes.elements.get(afterId)!;
        if (a.structure !== 'node' || b.structure !== 'node') throw fault('invalid_copy_endpoint');
        const from = toWorld(canvasTransform(document, a.ownerCanvasId), { x: a.geometry.x + a.geometry.width / 2, y: a.geometry.y + a.geometry.height / 2 }), to = toWorld(canvasTransform(nodes, b.ownerCanvasId), { x: b.geometry.x + b.geometry.width / 2, y: b.geometry.y + b.geometry.height / 2 });
        return { x: to.x - from.x, y: to.y - from.y };
      };
      const from = displacement(edge.source.elementId, source.elementId), to = displacement(edge.target.elementId, target.elementId), knots = path.knots;
      path = { ...path, knots: knots.map((raw, index) => { const knot = raw as Record<string, Json>, point = knot.position as { x: number; y: number }, world = toWorld(transform, point), t = (index + 1) / (knots.length + 1); return { ...knot, position: toLocal(transform, { x: world.x + from.x * (1 - t) + to.x * t, y: world.y + from.y * (1 - t) + to.y * t }) }; }) };
    }
    const after: ElementRecord = { ...clone(edge), id: elementIds.get(edge.id)!, incarnation: 1, ownerCanvasId: owner, source, target, path, data: remapCopyData(edge, registry, elementIds, canvasIds, document) };
    return { kind: 'element', id: after.id, before: null, after };
}
export function duplicateOverlay(document:Document,elements:ReadonlyMap<Id,ElementRecord>,canvases:ReadonlyMap<Id,CanvasRecord>):Document{return {...document,elements:overlay(document.elements,elements),canvases:overlay(document.canvases,canvases)};}

/** Internal overlay avoids an O(document size) clone between planning phases. Additions own unique IDs. */
function overlay<K,V>(base: ReadonlyMap<K,V>, additions: ReadonlyMap<K,V>): ReadonlyMap<K,V> {
  const view: ReadonlyMap<K,V> = {
    get size() { return base.size + additions.size; },
    get: key => additions.has(key) ? additions.get(key) : base.get(key), has: key => additions.has(key) || base.has(key),
    *entries(): Generator<[K,V],undefined> { yield* base; yield* additions; return undefined; },
    *keys(): Generator<K,undefined> { yield* base.keys(); yield* additions.keys(); return undefined; },
    *values(): Generator<V,undefined> { yield* base.values(); yield* additions.values(); return undefined; },
    [Symbol.iterator]() { return this.entries(); },
    forEach(callback,thisArg) { for (const [key,value] of view) callback.call(thisArg,value,key,view); },
  };
  return Object.freeze(view);
}

/** Synchronous API retained for small snapshots and callers that own scheduling. */
export function planDuplicate(document: Document, registry: Registry, selection: readonly Target[], options: DuplicateOptions): DuplicatePlan {
  const steps = planDuplicateSteps(document,registry,selection,options);
  while (true) { const step = steps.next(); if (step.done) return step.value; }
}