import { getDb } from '../db/database.js'

export interface DbExam {
  id: number
  user_id: number
  title: string
  subtitle: string | null
  exam_json: string
  created_at: number
  updated_at: number
  share_token: string | null
  is_public: number
  is_favorite: number
  tags: string | null
  share_mode: string | null
  cloned_from_share_token: string | null
}

export interface ExamListItem {
  id: number
  title: string
  subtitle: string | null
  created_at: number
  updated_at: number
  question_count: number
  share_token: string | null
  is_favorite: number
  tags: string
  collection_id: number | null
}

export function createExam(userId: number, title: string, subtitle: string | null, examJson: string, tagsJson: string = '[]'): { id: number } {
  const db = getDb()
  const result = db.prepare(`
    INSERT INTO saved_exams (user_id, title, subtitle, exam_json, tags)
    VALUES (?, ?, ?, ?, ?)
  `).run(userId, title, subtitle, examJson, tagsJson)
  return { id: result.lastInsertRowid as number }
}

export function getExamById(id: number, userId: number): DbExam | undefined {
  const db = getDb()
  return db.prepare('SELECT * FROM saved_exams WHERE id = ? AND user_id = ?').get(id, userId) as DbExam | undefined
}

export function listExamsByUser(userId: number): ExamListItem[] {
  const db = getDb()
  return db.prepare(`
    SELECT id, title, subtitle, created_at, updated_at, share_token, is_favorite, tags, collection_id,
           json_array_length(json_extract(exam_json, '$.questions')) AS question_count
    FROM saved_exams
    WHERE user_id = ?
    ORDER BY is_favorite DESC, updated_at DESC
  `).all(userId) as ExamListItem[]
}

export function updateExam(id: number, userId: number, title: string, subtitle: string | null, examJson: string, tagsJson: string | null = null): boolean {
  const db = getDb()
  if (tagsJson !== null) {
    const result = db.prepare(`
      UPDATE saved_exams
      SET title = ?, subtitle = ?, exam_json = ?, tags = ?, updated_at = unixepoch()
      WHERE id = ? AND user_id = ?
    `).run(title, subtitle, examJson, tagsJson, id, userId)
    return result.changes > 0
  }
  const result = db.prepare(`
    UPDATE saved_exams
    SET title = ?, subtitle = ?, exam_json = ?, updated_at = unixepoch()
    WHERE id = ? AND user_id = ?
  `).run(title, subtitle, examJson, id, userId)
  return result.changes > 0
}

export function deleteExam(id: number, userId: number): boolean {
  const db = getDb()
  const result = db.prepare('DELETE FROM saved_exams WHERE id = ? AND user_id = ?').run(id, userId)
  return result.changes > 0
}

export function countExams(): number {
  const db = getDb()
  const row = db.prepare('SELECT COUNT(*) AS cnt FROM saved_exams').get() as { cnt: number }
  return row.cnt
}

export function setShareToken(id: number, userId: number, token: string, mode: string = 'clone'): boolean {
  const db = getDb()
  const result = db.prepare(`
    UPDATE saved_exams
    SET share_token = ?, is_public = 1, share_mode = ?, updated_at = unixepoch()
    WHERE id = ? AND user_id = ?
  `).run(token, mode, id, userId)
  return result.changes > 0
}

export function clearShareToken(id: number, userId: number): boolean {
  const db = getDb()
  const result = db.prepare(`
    UPDATE saved_exams
    SET share_token = NULL, is_public = 0, share_mode = 'clone', updated_at = unixepoch()
    WHERE id = ? AND user_id = ?
  `).run(id, userId)
  return result.changes > 0
}

export function getExamByShareToken(token: string): DbExam | undefined {
  const db = getDb()
  return db.prepare('SELECT * FROM saved_exams WHERE share_token = ? AND is_public = 1').get(token) as DbExam | undefined
}

export function setShareMode(id: number, userId: number, mode: string): boolean {
  const db = getDb()
  const result = db.prepare(`
    UPDATE saved_exams
    SET share_mode = ?, updated_at = unixepoch()
    WHERE id = ? AND user_id = ?
  `).run(mode, id, userId)
  return result.changes > 0
}

export function cloneExam(userId: number, sourceExam: DbExam, shareToken: string): { id: number } {
  const db = getDb()
  const parsed = JSON.parse(sourceExam.exam_json)
  parsed.id = undefined
  const result = db.prepare(`
    INSERT INTO saved_exams (user_id, title, subtitle, exam_json, cloned_from_share_token)
    VALUES (?, ?, ?, ?, ?)
  `).run(userId, sourceExam.title + ' (copy)', sourceExam.subtitle, JSON.stringify(parsed), shareToken)
  return { id: result.lastInsertRowid as number }
}

export interface ClonedExamItem {
  id: number
  title: string
  subtitle: string | null
  created_at: number
  updated_at: number
  question_count: number
  cloned_from_share_token: string
}

export function listClonedExams(userId: number): ClonedExamItem[] {
  const db = getDb()
  return db.prepare(`
    SELECT id, title, subtitle, created_at, updated_at, cloned_from_share_token,
           json_array_length(json_extract(exam_json, '$.questions')) AS question_count
    FROM saved_exams
    WHERE user_id = ? AND cloned_from_share_token IS NOT NULL
    ORDER BY updated_at DESC
  `).all(userId) as ClonedExamItem[]
}

export function setFavorite(id: number, userId: number, isFavorite: boolean): boolean {
  const db = getDb()
  const result = db.prepare(`
    UPDATE saved_exams
    SET is_favorite = ?, updated_at = unixepoch()
    WHERE id = ? AND user_id = ?
  `).run(isFavorite ? 1 : 0, id, userId)
  return result.changes > 0
}

export function getExamRawJson(id: number, userId: number): { title: string; exam_json: string } | undefined {
  const db = getDb()
  return db.prepare('SELECT title, exam_json FROM saved_exams WHERE id = ? AND user_id = ?').get(id, userId) as { title: string; exam_json: string } | undefined
}

export function duplicateOwnExam(userId: number, sourceExam: DbExam): { id: number } {
  const db = getDb()
  const parsed = JSON.parse(sourceExam.exam_json)
  parsed.id = undefined
  const result = db.prepare(`
    INSERT INTO saved_exams (user_id, title, subtitle, exam_json, tags)
    VALUES (?, ?, ?, ?, ?)
  `).run(userId, sourceExam.title + ' (copy)', sourceExam.subtitle, JSON.stringify(parsed), sourceExam.tags ?? '[]')
  return { id: result.lastInsertRowid as number }
}

export function setExamCollection(id: number, userId: number, collectionId: number | null): boolean {
  const db = getDb()
  const result = db.prepare(`
    UPDATE saved_exams
    SET collection_id = ?, updated_at = unixepoch()
    WHERE id = ? AND user_id = ?
  `).run(collectionId, id, userId)
  return result.changes > 0
}