import type { FastifyInstance } from 'fastify';
import { z } from 'zod';
import type { Sql } from '../db.js';
import type { Config } from '../config.js';
import type { Broker } from '../services/broker.js';
import type { Session } from '../types/api.js';
import { getSetting } from './settings.js';

const CreateBody = z.object({
  name: z.string().min(1).max(200).optional(),
  model: z.string().min(1).max(200).optional(),
  system_prompt: z.string().max(8000).optional(),
});

const PatchBody = z.object({
  name: z.string().min(1).max(200).optional(),
  model: z.string().min(1).max(200).optional(),
  system_prompt: z.string().max(8000).optional(),
});

async function resolveDefaultModel(sql: Sql, config: Config): Promise<string> {
  const fromDb = await getSetting<string>(sql, 'default_model');
  if (typeof fromDb === 'string' && fromDb.length > 0) return fromDb;
  return config.DEFAULT_MODEL;
}

export function registerSessionRoutes(
  app: FastifyInstance,
  sql: Sql,
  config: Config,
  broker: Broker
): void {
  app.get<{ Params: { id: string }; Querystring: { status?: string } }>(
    '/api/projects/:id/sessions',
    async (req, reply) => {
      const project = await sql`SELECT id FROM projects WHERE id = ${req.params.id}`;
      if (project.length === 0) {
        reply.code(404);
        return { error: 'project not found' };
      }
      const status = req.query.status === 'archived' ? 'archived' : 'open';
      const rows = await sql<Session[]>`
        SELECT id, project_id, name, model, system_prompt, status, created_at, updated_at
        FROM sessions
        WHERE project_id = ${req.params.id} AND status = ${status}
        ORDER BY updated_at DESC
      `;
      return rows;
    }
  );

  app.post<{ Params: { id: string } }>(
    '/api/projects/:id/sessions',
    async (req, reply) => {
      const parsed = CreateBody.safeParse(req.body ?? {});
      if (!parsed.success) {
        reply.code(400);
        return { error: 'invalid body', details: parsed.error.flatten() };
      }
      const project = await sql`SELECT id FROM projects WHERE id = ${req.params.id}`;
      if (project.length === 0) {
        reply.code(404);
        return { error: 'project not found' };
      }

      let model = parsed.data.model;
      if (!model) {
        const lastUsed = await sql<{ model: string }[]>`
          SELECT model FROM sessions
          WHERE project_id = ${req.params.id}
          ORDER BY created_at DESC
          LIMIT 1
        `;
        model = lastUsed[0]?.model ?? (await resolveDefaultModel(sql, config));
      }

      const name = parsed.data.name ?? 'New session';
      const systemPrompt = parsed.data.system_prompt ?? '';

      const row = await sql.begin(async (tx) => {
        const [session] = await tx<Session[]>`
          INSERT INTO sessions (project_id, name, model, system_prompt)
          VALUES (${req.params.id}, ${name}, ${model}, ${systemPrompt})
          RETURNING id, project_id, name, model, system_prompt, status, created_at, updated_at
        `;
        await tx`
          INSERT INTO chats (session_id, name, status)
          VALUES (${session!.id}, NULL, 'open')
        `;
        return session!;
      });
      broker.publishUser('default', {
        type: 'session_created',
        session: row,
        project_id: row.project_id,
      });
      reply.code(201);
      return row;
    }
  );

  app.get<{ Params: { id: string } }>('/api/sessions/:id', async (req, reply) => {
    const rows = await sql<Session[]>`
      SELECT id, project_id, name, model, system_prompt, status, created_at, updated_at
      FROM sessions WHERE id = ${req.params.id}
    `;
    if (rows.length === 0) {
      reply.code(404);
      return { error: 'session not found' };
    }
    return rows[0];
  });

  app.patch<{ Params: { id: string } }>(
    '/api/sessions/:id',
    async (req, reply) => {
      const parsed = PatchBody.safeParse(req.body);
      if (!parsed.success) {
        reply.code(400);
        return { error: 'invalid body', details: parsed.error.flatten() };
      }
      const { name, model, system_prompt } = parsed.data;
      const rows = await sql<Session[]>`
        UPDATE sessions
        SET
          name = COALESCE(${name ?? null}, name),
          model = COALESCE(${model ?? null}, model),
          system_prompt = COALESCE(${system_prompt ?? null}, system_prompt),
          updated_at = clock_timestamp()
        WHERE id = ${req.params.id}
        RETURNING id, project_id, name, model, system_prompt, status, created_at, updated_at
      `;
      if (rows.length === 0) {
        reply.code(404);
        return { error: 'session not found' };
      }
      const session = rows[0]!;
      if (name !== undefined) {
        broker.publishUser('default', {
          type: 'session_renamed',
          session_id: session.id,
          name: session.name,
        });
      }
      return session;
    }
  );

  app.post<{ Params: { id: string } }>(
    '/api/sessions/:id/archive',
    async (req, reply) => {
      const rows = await sql<{ id: string; project_id: string }[]>`
        UPDATE sessions SET status = 'archived', updated_at = clock_timestamp()
        WHERE id = ${req.params.id} AND status = 'open'
        RETURNING id, project_id
      `;
      if (rows.length === 0) {
        reply.code(404);
        return { error: 'session not found or already archived' };
      }
      broker.publishUser('default', {
        type: 'session_archived',
        session_id: rows[0]!.id,
        project_id: rows[0]!.project_id,
      });
      reply.code(204);
      return null;
    }
  );

  app.post<{ Params: { id: string } }>(
    '/api/sessions/:id/unarchive',
    async (req, reply) => {
      const rows = await sql<Session[]>`
        UPDATE sessions SET status = 'open', updated_at = clock_timestamp()
        WHERE id = ${req.params.id} AND status = 'archived'
        RETURNING id, project_id, name, model, system_prompt, status, created_at, updated_at
      `;
      if (rows.length === 0) {
        reply.code(404);
        return { error: 'session not found or not archived' };
      }
      const session = rows[0]!;
      broker.publishUser('default', {
        type: 'session_created',
        session: session,
        project_id: session.project_id,
      });
      reply.code(200);
      return session;
    }
  );

  app.delete<{ Params: { id: string } }>(
    '/api/sessions/:id',
    async (req, reply) => {
      const id = req.params.id;
      const deleted = await sql<{ project_id: string }[]>`
        DELETE FROM sessions WHERE id = ${id} RETURNING project_id
      `;
      if (deleted.length === 0) {
        reply.code(404);
        return { error: 'not found' };
      }
      const project_id = deleted[0]!.project_id;
      broker.publishUser('default', { type: 'session_deleted', session_id: id, project_id });
      reply.code(204);
      return null;
    }
  );
}