/**
 * Consistency checks across entities and chapters. These catch the kinds of
 * contradictions that creep in as a manuscript grows: a character mentioned in
 * prose whose entity was deleted, or a relationship that only one side records.
 * See CHUNK #4 step 2.4.
 */
import type { Character, Entity, ProseMirrorDoc } from "./types.js";
import { collectMentionsInDoc } from "./backlinks.js";

export type RelationshipSymmetry = "symmetric" | "directed";

/**
 * Relationship kinds that should hold in both directions. If Ada lists "Bram:
 * sibling", then Bram should list "Ada: sibling" too.
 */
export const SYMMETRIC_RELATIONSHIPS = new Set(["sibling", "friend", "spouse", "partner", "family", "rival"]);

export interface MentionIssue {
  kind: "orphan-mention";
  chapterId: string;
  chapterTitle: string;
  entityId: string;
  /** The mention text, if any. */
  name?: string | undefined;
}

export interface RelationshipIssue {
  kind: "relationship-asymmetry";
  fromEntity: string;
  fromName: string;
  toEntity: string;
  toName: string;
  relationship: string;
}

export interface DeadCharacterIssue {
  kind: "dead-character-mentioned";
  chapterId: string;
  chapterTitle: string;
  entityId: string;
  /** The mention text, if any. */
  name?: string | undefined;
}

export type ConsistencyIssue = MentionIssue | RelationshipIssue | DeadCharacterIssue;

/**
 * Find mention nodes that reference an entity id that no longer exists (e.g.
 * the entity was deleted). Returns one issue per offending mention.
 */
export function findOrphanedMentions(
  chapters: Array<{ id: string; title: string; doc: ProseMirrorDoc }>,
  entityIds: Set<string>,
): MentionIssue[] {
  const issues: MentionIssue[] = [];
  for (const ch of chapters) {
    const mentioned = collectMentionsInDoc(ch.doc);
    for (const entityId of mentioned) {
      if (!entityIds.has(entityId)) {
        issues.push({
          kind: "orphan-mention",
          chapterId: ch.id,
          chapterTitle: ch.title,
          entityId,
        });
      }
    }
  }
  return issues;
}

/**
 * Find characters who are marked `dead` but are still mentioned (by entity id)
 * in a chapter body. A dead character should not appear alive in the story.
 *
 * Bare-name mentions (no `entityId`) are ignored — a reference to a name that
 * is not yet an entity is an orphan-mention concern, not a dead-character one.
 */
export function findDeadCharacterMentions(
  chapters: Array<{ id: string; title: string; doc: ProseMirrorDoc }>,
  entities: Entity[],
): DeadCharacterIssue[] {
  const dead = new Set(
    entities
      .filter((e): e is Character => !("fields" in e) && !("body" in e) && e.status === "dead")
      .map((c) => c.id),
  );
  const issues: DeadCharacterIssue[] = [];
  for (const chapter of chapters) {
    const mentioned = collectMentionsInDoc(chapter.doc);
    for (const entityId of mentioned) {
      if (dead.has(entityId)) {
        issues.push({
          kind: "dead-character-mentioned",
          chapterId: chapter.id,
          chapterTitle: chapter.title,
          entityId,
        });
      }
    }
  }
  return issues;
}

/**
 * Parse the `relationships` array of a character into
 * `{ [targetId]: { kind, note } }`.
 */
export function parseRelationships(character: Character): Record<string, { kind: string; note: string }> {
  const out: Record<string, { kind: string; note: string }> = {};
  for (const r of character.relationships ?? []) {
    out[r.targetId] = { kind: r.kind, note: r.note };
  }
  return out;
}

/**
 * Find relationships recorded by one character but not reciprocated by the
 * other, for symmetric relationship kinds. Returns one issue per asymmetric
 * pair (reported once, from the recording side).
 */
export function findRelationshipAsymmetry(entities: Entity[]): RelationshipIssue[] {
  const characters = entities.filter((e): e is Character => !("fields" in e) && !("body" in e));
  // index by id -> character (targetId is an entity id)
  const byId = new Map<string, Character>();
  for (const c of characters) byId.set(c.id, c);

  const issues: RelationshipIssue[] = [];
  for (const c of characters) {
    const rels = parseRelationships(c);
    for (const [targetId, rel] of Object.entries(rels)) {
      const sym = rel.kind.toLowerCase();
      if (!SYMMETRIC_RELATIONSHIPS.has(sym)) continue;
      const other = byId.get(targetId);
      if (!other || other.id === c.id) continue;
      // Does the other side record this character back with a symmetric kind?
      const otherRel = parseRelationships(other);
      const back = otherRel[c.id];
      if (!back || !SYMMETRIC_RELATIONSHIPS.has(back.kind.toLowerCase())) {
        issues.push({
          kind: "relationship-asymmetry",
          fromEntity: c.id,
          fromName: c.name,
          toEntity: other.id,
          toName: other.name,
          relationship: rel.kind,
        });
      }
    }
  }
  return issues;
}

/** Run every consistency check and return the combined issue list. */
export function findInconsistencies(
  chapters: Array<{ id: string; title: string; doc: ProseMirrorDoc }>,
  entities: Entity[],
): ConsistencyIssue[] {
  const entityIds = new Set(entities.map((e) => e.id));
  const issues: ConsistencyIssue[] = [
    ...findOrphanedMentions(chapters, entityIds),
    ...findRelationshipAsymmetry(entities),
    ...findDeadCharacterMentions(chapters, entities),
  ];
  return issues;
}