import { Inject, Injectable, forwardRef } from '@nestjs/common'
import { DatabaseService } from '../database/database.service'
import {
  GOLD_LAND_LEVELS,
  GOLD_LAND_MAX_STARS,
  getLevelDefinition,
} from './levels'
import type { UserState } from '../shared/types/user.types'
import { UsersService } from '../users/users.service'

type LevelStatus = 'locked' | 'available' | 'in_progress' | 'completed' | 'coming_soon'

interface LevelProgressRow {
  user_id: string
  level_id: number
  best_score: number
  stars: number
  attempts_count: number
  started_at: string | null
  completed_at: string | null
  updated_at: string
}

interface LevelItemResponse {
  id: number
  order: number
  slug: string
  title: string
  description: string
  status: LevelStatus
  stars: 0 | 1 | 2 | 3
  bestScore: number
  activityType: string
  activityKey: string
  activityRoute?: string
  rewardXp: number
  rewardCoins: number
}

@Injectable()
export class ProgressionSyncService {
  constructor(
    @Inject(DatabaseService) private readonly database: DatabaseService,
    @Inject(forwardRef(() => UsersService))
    private readonly users: UsersService,
  ) {}

  syncUserProgressionState(userId: string): UserState {
    return this.database.transaction(() => {
      const state = this.users.getUserState(userId)
      const items = this.buildLevelItems(userId)
      this.syncLegacyMapLevels(state, items)
      return this.users.saveUserState(state)
    })
  }

  private getProgressRow(userId: string, levelId: number): LevelProgressRow | undefined {
    return this.database
      .getDb()
      .prepare('SELECT * FROM user_level_progress WHERE user_id = ? AND level_id = ?')
      .get(userId, levelId) as LevelProgressRow | undefined
  }

  private getAllProgressRows(userId: string): LevelProgressRow[] {
    return this.database
      .getDb()
      .prepare('SELECT * FROM user_level_progress WHERE user_id = ?')
      .all(userId) as LevelProgressRow[]
  }

  private migrateFromLegacyState(userId: string): void {
    const existing = this.getAllProgressRows(userId)
    if (existing.length > 0) return

    const state = this.users.getUserState(userId)
    const now = new Date().toISOString()
    const db = this.database.getDb()
    const insert = db.prepare(`
      INSERT INTO user_level_progress (
        user_id, level_id, best_score, stars, attempts_count,
        started_at, completed_at, updated_at
      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)
    `)

    this.database.transaction(() => {
      for (const legacy of state.mapLevels) {
        if (legacy.stars <= 0 && legacy.status !== 'completed') continue
        insert.run(
          userId,
          legacy.id,
          legacy.stars > 0 ? legacy.stars * 30 : 0,
          legacy.stars,
          legacy.stars > 0 ? 1 : 0,
          legacy.stars > 0 ? now : null,
          legacy.status === 'completed' && legacy.stars > 0 ? now : null,
          now,
        )
      }
    })
  }

  private isLevelUnlocked(levelId: number, rowsById: Map<number, LevelProgressRow>): boolean {
    if (levelId === 1) return true
    const prevStars = rowsById.get(levelId - 1)?.stars ?? 0
    return prevStars >= 1
  }

  private resolveLevelStatus(
    levelId: number,
    progress: LevelProgressRow | undefined,
    rowsById: Map<number, LevelProgressRow>,
  ): LevelStatus {
    const definition = getLevelDefinition(levelId)
    if (!definition) return 'locked'

    if ((progress?.stars ?? 0) > 0) return 'completed'
    if (progress?.started_at && !progress.completed_at) return 'in_progress'

    if (!this.isLevelUnlocked(levelId, rowsById)) return 'locked'

    if (!definition.isActive) return 'coming_soon'

    return 'available'
  }

  private buildLevelItems(userId: string): LevelItemResponse[] {
    this.migrateFromLegacyState(userId)
    const rows = this.getAllProgressRows(userId)
    const byId = new Map(rows.map((row) => [row.level_id, row]))

    return GOLD_LAND_LEVELS.map((definition) => {
      const progress = byId.get(definition.id)
      const status = this.resolveLevelStatus(definition.id, progress, byId)

      return {
        id: definition.id,
        order: definition.order,
        slug: definition.slug,
        title: definition.title,
        description: definition.description,
        status,
        stars: (progress?.stars ?? 0) as 0 | 1 | 2 | 3,
        bestScore: progress?.best_score ?? 0,
        activityType: definition.activityType,
        activityKey: definition.activityKey,
        activityRoute: definition.activityRoute,
        rewardXp: definition.rewardXp,
        rewardCoins: definition.rewardCoins,
      }
    })
  }

  private syncLegacyMapLevels(state: UserState, items: LevelItemResponse[]): void {
    state.mapLevels = items.map((item) => ({
      id: item.id,
      title: item.title,
      stars: item.stars,
      maxStars: 3,
      status: this.mapStatusToLegacy(item.status),
      lessonRoute: item.activityRoute,
      x: 0,
      y: 0,
    }))
    state.totalStars = items.reduce((sum, item) => sum + item.stars, 0)
    state.maxStars = GOLD_LAND_MAX_STARS
  }

  private mapStatusToLegacy(status: LevelStatus): UserState['mapLevels'][number]['status'] {
    switch (status) {
      case 'completed':
        return 'completed'
      case 'in_progress':
        return 'current'
      case 'available':
        return 'unlocked'
      case 'coming_soon':
        return 'locked'
      default:
        return 'locked'
    }
  }
}