import { Injectable, Logger, OnModuleDestroy, OnModuleInit } from "@nestjs/common";
import { PrismaClient } from "@prisma/client";

/**
 * Prisma service that manages database connection lifecycle
 * Extends PrismaClient to provide connection management and health checks
 */
@Injectable()
export class PrismaService extends PrismaClient implements OnModuleInit, OnModuleDestroy {
  private readonly logger = new Logger(PrismaService.name);

  constructor() {
    super({
      log: process.env.NODE_ENV === "development" ? ["query", "info", "warn", "error"] : ["error"],
    });
  }

  /**
   * Connect to database when NestJS module initializes
   */
  async onModuleInit() {
    try {
      await this.$connect();
      this.logger.log("Database connection established");
    } catch (error) {
      this.logger.error("Failed to connect to database", error);
      throw error;
    }
  }

  /**
   * Disconnect from database when NestJS module is destroyed
   */
  async onModuleDestroy() {
    await this.$disconnect();
    this.logger.log("Database connection closed");
  }

  /**
   * Health check for database connectivity
   * @returns true if database is accessible, false otherwise
   */
  async isHealthy(): Promise<boolean> {
    try {
      await this.$queryRaw`SELECT 1`;
      return true;
    } catch (error) {
      this.logger.error("Database health check failed", error);
      return false;
    }
  }

  /**
   * Get database connection info for debugging
   * @returns Connection status and basic info
   */
  async getConnectionInfo(): Promise<{
    connected: boolean;
    database?: string;
    version?: string;
  }> {
    try {
      const result = await this.$queryRaw<{ current_database: string; version: string }[]>`
        SELECT current_database(), version()
      `;

      if (result.length > 0 && result[0]) {
        const dbVersion = result[0].version.split(" ")[0];
        return {
          connected: true,
          database: result[0].current_database,
          ...(dbVersion && { version: dbVersion }),
        };
      }

      return { connected: false };
    } catch (error) {
      this.logger.error("Failed to get connection info", error);
      return { connected: false };
    }
  }

  /**
   * Sets workspace context for Row-Level Security (RLS)
   * Sets both user_id and workspace_id session variables for PostgreSQL RLS policies
   *
   * IMPORTANT: Must be called within a transaction or use the default client
   * Session variables are transaction-scoped (SET LOCAL) for connection pool safety
   *
   * @param userId - The ID of the authenticated user
   * @param workspaceId - The ID of the workspace context
   * @param client - Optional Prisma client (uses 'this' if not provided)
   *
   * @example
   * ```typescript
   * await prisma.$transaction(async (tx) => {
   *   await prisma.setWorkspaceContext(userId, workspaceId, tx);
   *   const tasks = await tx.task.findMany(); // Filtered by RLS
   * });
   * ```
   */
  async setWorkspaceContext(
    userId: string,
    workspaceId: string,
    client: PrismaClient = this
  ): Promise<void> {
    await client.$executeRaw`SET LOCAL app.current_user_id = ${userId}`;
    await client.$executeRaw`SET LOCAL app.current_workspace_id = ${workspaceId}`;
  }

  /**
   * Clears workspace context session variables
   * Typically not needed as SET LOCAL is automatically cleared at transaction end
   *
   * @param client - Optional Prisma client (uses 'this' if not provided)
   */
  async clearWorkspaceContext(client: PrismaClient = this): Promise<void> {
    await client.$executeRaw`SET LOCAL app.current_user_id = NULL`;
    await client.$executeRaw`SET LOCAL app.current_workspace_id = NULL`;
  }

  /**
   * Executes a function with workspace context set within a transaction
   * Automatically sets the context and ensures proper scoping
   *
   * @param userId - The ID of the authenticated user
   * @param workspaceId - The ID of the workspace context
   * @param fn - Function to execute with context (receives transaction client)
   * @returns The result of the function
   *
   * @example
   * ```typescript
   * const tasks = await prisma.withWorkspaceContext(userId, workspaceId, async (tx) => {
   *   return tx.task.findMany({
   *     where: { status: 'IN_PROGRESS' }
   *   });
   * });
   * ```
   */
  async withWorkspaceContext<T>(
    userId: string,
    workspaceId: string,
    fn: (tx: PrismaClient) => Promise<T>
  ): Promise<T> {
    return this.$transaction(async (tx) => {
      await this.setWorkspaceContext(userId, workspaceId, tx as PrismaClient);
      return fn(tx as PrismaClient);
    });
  }
}