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

export interface DbResult {
  id: number
  user_id: number
  exam_id: number | null
  title: string
  score_points: number
  total_points: number
  correct_count: number
  graded_count: number
  passing_score: number
  elapsed_ms: number
  state_json: string
  exam_json: string
  completed_at: number
}

export interface ResultListItem {
  id: number
  title: string
  score_points: number
  total_points: number
  correct_count: number
  graded_count: number
  passing_score: number
  elapsed_ms: number
  completed_at: number
  exam_id: number | null
}

export function createResult(data: Omit<DbResult, 'id'>): { id: number } {
  const db = getDb()
  const result = db.prepare(`
    INSERT INTO exam_results (user_id, exam_id, title, score_points, total_points, correct_count, graded_count, passing_score, elapsed_ms, state_json, exam_json)
    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
  `).run(
    data.user_id,
    data.exam_id ?? null,
    data.title,
    data.score_points,
    data.total_points,
    data.correct_count,
    data.graded_count,
    data.passing_score ?? 60,
    data.elapsed_ms ?? 0,
    data.state_json,
    data.exam_json
  )
  return { id: result.lastInsertRowid as number }
}

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

export function listResultsByUser(userId: number, options: { limit?: number; offset?: number } = {}): { results: ResultListItem[]; total: number } {
  const db = getDb()
  const limit = Math.min(options.limit ?? 30, 100)
  const offset = options.offset ?? 0

  const results = db.prepare(`
    SELECT id, title, score_points, total_points, correct_count, graded_count,
           passing_score, elapsed_ms, completed_at, exam_id
    FROM exam_results
    WHERE user_id = ?
    ORDER BY completed_at DESC
    LIMIT ? OFFSET ?
  `).all(userId, limit, offset) as ResultListItem[]

  const countRow = db.prepare('SELECT COUNT(*) AS total FROM exam_results WHERE user_id = ?').get(userId) as { total: number }

  return { results, total: countRow.total }
}

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

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

export function getAverageScore(): number {
  const db = getDb()
  const row = db.prepare(
    'SELECT COALESCE(AVG(score_points * 100.0 / NULLIF(total_points, 0)), 0) AS avg FROM exam_results'
  ).get() as { avg: number }
  return Math.round(row.avg * 10) / 10
}

export function getRecentResults(limit: number): Array<DbResult & { display_name: string; email: string }> {
  const db = getDb()
  return db.prepare(`
    SELECT er.*, u.display_name, u.email
    FROM exam_results er
    JOIN users u ON u.id = er.user_id
    ORDER BY er.completed_at DESC
    LIMIT ?
  `).all(limit) as Array<DbResult & { display_name: string; email: string }>
}

export function countResultsByUser(userId: number): number {
  const db = getDb()
  const row = db.prepare('SELECT COUNT(*) AS cnt FROM exam_results WHERE user_id = ?').get(userId) as { cnt: number }
  return row.cnt
}

export function getResultsWithExamJson(userId: number, limit = 100): Array<{
  title: string
  score_points: number
  total_points: number
  correct_count: number
  graded_count: number
  completed_at: number
  exam_json: string
  exam_id: number | null
}> {
  const db = getDb()
  return db.prepare(`
    SELECT title, score_points, total_points, correct_count, graded_count, completed_at, exam_json, exam_id
    FROM exam_results
    WHERE user_id = ?
    ORDER BY completed_at DESC
    LIMIT ?
  `).all(userId, limit) as Array<{
    title: string
    score_points: number
    total_points: number
    correct_count: number
    graded_count: number
    completed_at: number
    exam_json: string
    exam_id: number | null
  }>
}

export interface ScoreTrend {
  completed_at: number
  score_pct: number
  title: string
  exam_id: number | null
}

export function getScoreTrends(userId: number, limit = 30): Array<{
  completed_at: number
  score_points: number
  total_points: number
  title: string
  exam_id: number | null
}> {
  const db = getDb()
  return db.prepare(`
    SELECT completed_at, score_points, total_points, title, exam_id
    FROM exam_results
    WHERE user_id = ? AND total_points > 0
    ORDER BY completed_at ASC
    LIMIT ?
  `).all(userId, limit) as Array<{
    completed_at: number
    score_points: number
    total_points: number
    title: string
    exam_id: number | null
  }>
}