import { type Client, createClient } from '@libsql/client'
import { loggerService } from '@logger'
import { ModelValidationError, validateModelId } from '@main/apiServer/utils'
import { AgentType, objectKeys, Provider } from '@types'
import { drizzle, type LibSQLDatabase } from 'drizzle-orm/libsql'
import fs from 'fs'
import path from 'path'

import { MigrationService } from './database/MigrationService'
import * as schema from './database/schema'
import { dbPath } from './drizzle.config'
import { AgentModelField, AgentModelValidationError } from './errors'

const logger = loggerService.withContext('BaseService')

/**
 * Base service class providing shared database connection and utilities
 * for all agent-related services.
 *
 * Features:
 * - Programmatic schema management (no CLI dependencies)
 * - Automatic table creation and migration
 * - Schema version tracking and compatibility checks
 * - Transaction-based operations for safety
 * - Development vs production mode handling
 * - Connection retry logic with exponential backoff
 */
export abstract class BaseService {
  protected static client: Client | null = null
  protected static db: LibSQLDatabase<typeof schema> | null = null
  protected static isInitialized = false
  protected static initializationPromise: Promise<void> | null = null
  protected jsonFields: string[] = ['built_in_tools', 'mcps', 'configuration', 'accessible_paths', 'allowed_tools']

  /**
   * Initialize database with retry logic and proper error handling
   */
  protected static async initialize(): Promise<void> {
    // Return existing initialization if in progress
    if (BaseService.initializationPromise) {
      return BaseService.initializationPromise
    }

    if (BaseService.isInitialized) {
      return
    }

    BaseService.initializationPromise = BaseService.performInitialization()
    return BaseService.initializationPromise
  }

  private static async performInitialization(): Promise<void> {
    const maxRetries = 3
    let lastError: Error

    for (let attempt = 1; attempt <= maxRetries; attempt++) {
      try {
        logger.info(`Initializing Agent database at: ${dbPath} (attempt ${attempt}/${maxRetries})`)

        // Ensure the database directory exists
        const dbDir = path.dirname(dbPath)
        if (!fs.existsSync(dbDir)) {
          logger.info(`Creating database directory: ${dbDir}`)
          fs.mkdirSync(dbDir, { recursive: true })
        }

        BaseService.client = createClient({
          url: `file:${dbPath}`
        })

        BaseService.db = drizzle(BaseService.client, { schema })

        // Run database migrations
        const migrationService = new MigrationService(BaseService.db, BaseService.client)
        await migrationService.runMigrations()

        BaseService.isInitialized = true
        logger.info('Agent database initialized successfully')
        return
      } catch (error) {
        lastError = error as Error
        logger.warn(`Database initialization attempt ${attempt} failed:`, lastError)

        // Clean up on failure
        if (BaseService.client) {
          try {
            BaseService.client.close()
          } catch (closeError) {
            logger.warn('Failed to close client during cleanup:', closeError as Error)
          }
        }
        BaseService.client = null
        BaseService.db = null

        // Wait before retrying (exponential backoff)
        if (attempt < maxRetries) {
          const delay = Math.pow(2, attempt) * 1000 // 2s, 4s, 8s
          logger.info(`Retrying in ${delay}ms...`)
          await new Promise((resolve) => setTimeout(resolve, delay))
        }
      }
    }

    // All retries failed
    BaseService.initializationPromise = null
    logger.error('Failed to initialize Agent database after all retries:', lastError!)
    throw lastError!
  }

  protected ensureInitialized(): void {
    if (!BaseService.isInitialized || !BaseService.db || !BaseService.client) {
      throw new Error('Database not initialized. Call initialize() first.')
    }
  }

  protected get database(): LibSQLDatabase<typeof schema> {
    this.ensureInitialized()
    return BaseService.db!
  }

  protected get rawClient(): Client {
    this.ensureInitialized()
    return BaseService.client!
  }

  protected serializeJsonFields(data: any): any {
    const serialized = { ...data }

    for (const field of this.jsonFields) {
      if (serialized[field] !== undefined) {
        serialized[field] =
          Array.isArray(serialized[field]) || typeof serialized[field] === 'object'
            ? JSON.stringify(serialized[field])
            : serialized[field]
      }
    }

    return serialized
  }

  protected deserializeJsonFields(data: any): any {
    if (!data) return data

    const deserialized = { ...data }

    for (const field of this.jsonFields) {
      if (deserialized[field] && typeof deserialized[field] === 'string') {
        try {
          deserialized[field] = JSON.parse(deserialized[field])
        } catch (error) {
          logger.warn(`Failed to parse JSON field ${field}:`, error as Error)
        }
      }
    }

    // convert null from db to undefined to satisfy type definition
    for (const key of objectKeys(data)) {
      if (deserialized[key] === null) {
        deserialized[key] = undefined
      }
    }

    return deserialized
  }

  /**
   * Validate, normalize, and ensure filesystem access for a set of absolute paths.
   *
   * - Requires every entry to be an absolute path and throws if not.
   * - Normalizes each path and deduplicates while preserving order.
   * - Creates missing directories (or parent directories for file-like paths).
   */
  protected ensurePathsExist(paths?: string[]): string[] {
    if (!paths?.length) {
      return []
    }

    const sanitizedPaths: string[] = []
    const seenPaths = new Set<string>()

    for (const rawPath of paths) {
      if (!rawPath) {
        continue
      }

      if (!path.isAbsolute(rawPath)) {
        throw new Error(`Accessible path must be absolute: ${rawPath}`)
      }

      // Normalize to provide consistent values to downstream consumers.
      const resolvedPath = path.normalize(rawPath)

      let stats: fs.Stats | null = null
      try {
        // Attempt to stat the path to understand whether it already exists and if it is a file.
        if (fs.existsSync(resolvedPath)) {
          stats = fs.statSync(resolvedPath)
        }
      } catch (error) {
        logger.warn('Failed to inspect accessible path', {
          path: rawPath,
          error: error instanceof Error ? error.message : String(error)
        })
      }

      const looksLikeFile =
        (stats && stats.isFile()) || (!stats && path.extname(resolvedPath) !== '' && !resolvedPath.endsWith(path.sep))

      // For file-like targets create the parent directory; otherwise ensure the directory itself.
      const directoryToEnsure = looksLikeFile ? path.dirname(resolvedPath) : resolvedPath

      if (!fs.existsSync(directoryToEnsure)) {
        try {
          fs.mkdirSync(directoryToEnsure, { recursive: true })
        } catch (error) {
          logger.error('Failed to create accessible path directory', {
            path: directoryToEnsure,
            error: error instanceof Error ? error.message : String(error)
          })
          throw error
        }
      }

      // Preserve the first occurrence only to avoid duplicates while keeping caller order stable.
      if (!seenPaths.has(resolvedPath)) {
        seenPaths.add(resolvedPath)
        sanitizedPaths.push(resolvedPath)
      }
    }

    return sanitizedPaths
  }

  /**
   * Force re-initialization (for development/testing)
   */
  protected async validateAgentModels(
    agentType: AgentType,
    models: Partial<Record<AgentModelField, string | undefined>>
  ): Promise<void> {
    const entries = Object.entries(models) as [AgentModelField, string | undefined][]
    if (entries.length === 0) {
      return
    }

    for (const [field, rawValue] of entries) {
      if (rawValue === undefined || rawValue === null) {
        continue
      }

      const modelValue = rawValue
      const validation = await validateModelId(modelValue)

      if (!validation.valid || !validation.provider) {
        const detail: ModelValidationError = validation.error ?? {
          type: 'invalid_format',
          message: 'Unknown model validation error',
          code: 'validation_error'
        }

        throw new AgentModelValidationError({ agentType, field, model: modelValue }, detail)
      }

      if (!validation.provider.apiKey) {
        throw new AgentModelValidationError(
          { agentType, field, model: modelValue },
          {
            type: 'invalid_format',
            message: `Provider '${validation.provider.id}' is missing an API key`,
            code: 'provider_api_key_missing'
          }
        )
      }

      // different agent types may have different provider requirements
      const agentTypeProviderRequirements: Record<AgentType, Provider['type']> = {
        'claude-code': 'anthropic'
      }
      for (const [ak, pk] of Object.entries(agentTypeProviderRequirements)) {
        if (agentType === ak && validation.provider.type !== pk) {
          throw new AgentModelValidationError(
            { agentType, field, model: modelValue },
            {
              type: 'unsupported_provider_type',
              message: `Provider type '${validation.provider.type}' is not supported for agent type '${agentType}'. Expected '${pk}'`,
              code: 'unsupported_provider_type'
            }
          )
        }
      }
    }
  }

  static async reinitialize(): Promise<void> {
    BaseService.isInitialized = false
    BaseService.initializationPromise = null

    if (BaseService.client) {
      try {
        BaseService.client.close()
      } catch (error) {
        logger.warn('Failed to close client during reinitialize:', error as Error)
      }
    }

    BaseService.client = null
    BaseService.db = null

    await BaseService.initialize()
  }
}