/**
 * Arena routes — HTTP surface for the Battle UI.
 *
 * POST /api/battles                         — launch a battle
 * GET  /api/battles?project_id=             — list battles for a project
 * GET  /api/battles/:id                     — one battle + contestants + cross-exams
 * POST /api/battles/:id/stop                — cancel a running battle
 * POST /api/battles/:id/analyze             — trigger analysis (Phase 5 fills the logic)
 * POST /api/battles/:id/cross-examine       — start a cross-examination (Phase 5 fills the logic)
 *
 * Mirrors the shape of runs.ts (Orchestrator routes). Battle creation delegates to
 * the battle-runner; cancellation calls cancelBattle then aborts in-flight tasks
 * via the dispatcher's cancelExternalTask.
 */
import type { FastifyInstance } from 'fastify';
import { z } from 'zod';
import { readFile } from 'node:fs/promises';
import { join } from 'node:path';
import type { Sql } from '../db.js';
import type { Config } from '../config.js';
import type { BattleRunner } from '../services/arena-runner.js';
import type { ExternalCancelFn } from './tasks.js';
import { arenaModelCall } from '../services/arena-model-call.js';

// ─── Validation schemas ───────────────────────────────────────────────────────

const UuidParam = z.string().uuid();

const ContestantInput = z.object({
  identity: z.string().min(1).max(200),
  model: z.string().min(1).max(200),
});

const CreateBattleBody = z.object({
  project_id: z.string().uuid(),
  battle_type: z.enum(['coding', 'qa']),
  prompt: z.string().min(1).max(64_000),
  contestants: z
    .array(ContestantInput)
    .min(2, 'at least 2 contestants required')
    .max(6, 'at most 6 contestants allowed'),
});

const ListBattlesQuery = z.object({
  project_id: z.string().uuid(),
});

const CrossExamineBody = z.object({
  identity: z.string().min(1).max(200),
  model: z.string().min(1).max(200),
});

const SetWinnerBody = z.object({
  winner_contestant_id: z.string().uuid().nullable(),
});

// ─── Route registration ───────────────────────────────────────────────────────

const GeneratePromptBody = z.object({
  description: z.string().min(1).max(2_000),
});

export function registerArenaRoutes(
  app: FastifyInstance,
  sql: Sql,
  battleRunner: BattleRunner,
  cancelExternal: ExternalCancelFn,
  config: Config,
): void {

  // POST /api/battles/generate-prompt — draft a fuller battle prompt from a
  // short description using the default BooChat model. One-shot, non-streaming.
  // Must be registered BEFORE /api/battles/:id so the literal 'generate-prompt'
  // path is not mistaken for a UUID param.
  app.post('/api/battles/generate-prompt', async (req, reply) => {
    const parsed = GeneratePromptBody.safeParse(req.body);
    if (!parsed.success) {
      reply.code(400);
      return { error: 'invalid body', details: parsed.error.flatten() };
    }

    const { description } = parsed.data;

    try {
      const prompt = await arenaModelCall({
        config,
        model: config.DEFAULT_MODEL,
        system: [
          'You are a battle-prompt writer for an AI Arena.',
          'The user gives you a short description of a coding or Q&A challenge.',
          'Expand it into a clear, self-contained prompt (2–6 sentences) that any AI model can act on.',
          'Include specific acceptance criteria where helpful.',
          'Output ONLY the prompt — no preamble, no labels, no meta-commentary.',
        ].join(' '),
        user: description,
        maxTokens: 400,
        temperature: 0.6,
      });
      return { prompt };
    } catch (err) {
      app.log.warn(
        { err: err instanceof Error ? err.message : String(err) },
        'arena generate-prompt: model call failed',
      );
      reply.code(502);
      return { error: 'model call failed' };
    }
  });

  // POST /api/battles — launch a battle
  app.post('/api/battles', async (req, reply) => {
    const parsed = CreateBattleBody.safeParse(req.body);
    if (!parsed.success) {
      reply.code(400);
      return { error: 'invalid body', details: parsed.error.flatten() };
    }

    const { project_id, battle_type, prompt, contestants } = parsed.data;

    // Reject duplicate (identity, model) pairs up front — the schema UNIQUE
    // constraint would catch it too, but an early 422 is friendlier.
    const seen = new Set<string>();
    for (const c of contestants) {
      const key = `${c.identity}::${c.model}`;
      if (seen.has(key)) {
        reply.code(422);
        return {
          error: 'duplicate_contestant',
          message: `duplicate contestant: identity="${c.identity}" model="${c.model}"`,
        };
      }
      seen.add(key);
    }

    // Verify project exists
    const [proj] = await sql<{ id: string }[]>`SELECT id FROM projects WHERE id = ${project_id}`;
    if (!proj) {
      reply.code(404);
      return { error: 'project not found' };
    }

    const { battleId } = await battleRunner.startBattle({
      projectId: project_id,
      battleType: battle_type,
      prompt,
      contestants,
    });

    reply.code(201);
    return { battle_id: battleId };
  });

  // GET /api/battles?project_id= — list battles, most-recent-first
  app.get('/api/battles', async (req, reply) => {
    const parsed = ListBattlesQuery.safeParse(req.query);
    if (!parsed.success) {
      reply.code(400);
      return { error: 'invalid query', details: parsed.error.flatten() };
    }

    const battles = await sql`
      SELECT id, project_id, battle_type, prompt, status,
             winner_contestant_id, results_path, error,
             created_at, updated_at
      FROM battles
      WHERE project_id = ${parsed.data.project_id}
      ORDER BY created_at DESC
      LIMIT 100
    `;

    return { battles };
  });

  // GET /api/battles/:id — one battle + its contestants + cross-examinations
  app.get<{ Params: { id: string } }>('/api/battles/:id', async (req, reply) => {
    const parsedId = UuidParam.safeParse(req.params.id);
    if (!parsedId.success) {
      reply.code(400);
      return { error: 'invalid id' };
    }
    const id = parsedId.data;

    const [battle] = await sql<{
      id: string;
      project_id: string;
      battle_type: string;
      prompt: string;
      status: string;
      winner_contestant_id: string | null;
      results_path: string | null;
      error: string | null;
      created_at: unknown;
      updated_at: unknown;
    }[]>`
      SELECT id, project_id, battle_type, prompt, status,
             winner_contestant_id, results_path, error,
             created_at, updated_at
      FROM battles WHERE id = ${id}
    `;

    if (!battle) {
      reply.code(404);
      return { error: 'battle not found' };
    }

    const contestants = await sql`
      SELECT id, battle_id, identity, model, lane, task_id, worktree_id,
             status, duration_ms, tokens_per_sec, cost_tokens, token_breakdown, result_path, error,
             created_at, updated_at
      FROM contestants
      WHERE battle_id = ${id}
      ORDER BY created_at ASC
    `;

    const crossExaminations = await sql`
      SELECT id, battle_id, identity, model, verdict, created_at
      FROM cross_examinations
      WHERE battle_id = ${id}
      ORDER BY created_at ASC
    `;

    return { battle, contestants, cross_examinations: crossExaminations };
  });

  // POST /api/battles/:id/stop — cancel a running battle
  app.post<{ Params: { id: string } }>('/api/battles/:id/stop', async (req, reply) => {
    const parsedId = UuidParam.safeParse(req.params.id);
    if (!parsedId.success) {
      reply.code(400);
      return { error: 'invalid id' };
    }
    const id = parsedId.data;

    const [row] = await sql<{ id: string; status: string }[]>`
      SELECT id, status FROM battles WHERE id = ${id}
    `;
    if (!row) {
      reply.code(404);
      return { error: 'battle not found' };
    }
    if (row.status !== 'running') {
      reply.code(409);
      return { error: `cannot stop battle in status '${row.status}'` };
    }

    const { cancelled, taskIds } = await battleRunner.cancelBattle(id);
    if (!cancelled) {
      reply.code(409);
      return { error: 'battle is no longer running' };
    }

    // Abort any in-flight dispatcher tasks (cloud contestants running externally).
    for (const taskId of taskIds) {
      cancelExternal(taskId);
    }

    return { cancelled: true };
  });

  // GET /api/battles/:id/analysis — read analysis.md from the battle's results_path
  app.get<{ Params: { id: string } }>('/api/battles/:id/analysis', async (req, reply) => {
    const parsedId = UuidParam.safeParse(req.params.id);
    if (!parsedId.success) {
      reply.code(400);
      return { error: 'invalid id' };
    }
    const id = parsedId.data;

    const [row] = await sql<{ results_path: string | null }[]>`
      SELECT results_path FROM battles WHERE id = ${id}
    `;
    if (!row) {
      reply.code(404);
      return { error: 'battle not found' };
    }
    if (!row.results_path) {
      reply.code(404);
      return { error: 'analysis not ready' };
    }

    try {
      const text = await readFile(join(row.results_path, 'analysis.md'), 'utf8');
      return { text };
    } catch {
      reply.code(404);
      return { error: 'analysis not ready' };
    }
  });

  // POST /api/battles/:id/analyze — trigger or re-trigger analysis
  app.post<{ Params: { id: string } }>('/api/battles/:id/analyze', async (req, reply) => {
    const parsedId = UuidParam.safeParse(req.params.id);
    if (!parsedId.success) {
      reply.code(400);
      return { error: 'invalid id' };
    }
    const id = parsedId.data;

    const [row] = await sql<{ id: string; status: string }[]>`
      SELECT id, status FROM battles WHERE id = ${id}
    `;
    if (!row) {
      reply.code(404);
      return { error: 'battle not found' };
    }
    if (row.status === 'running') {
      reply.code(409);
      return { error: 'battle is still running — wait for all contestants to finish' };
    }

    const result = await battleRunner.triggerAnalysis(id);
    if (!result.triggered) {
      reply.code(404);
      return { error: 'battle not found' };
    }

    reply.code(202);
    return { triggered: true };
  });

  // PATCH /api/battles/:id/winner — manually set or clear the winner.
  // Validates the contestant belongs to the battle; publishes battle_updated so
  // the pane badge reflects the override immediately. Human is authoritative.
  app.patch<{ Params: { id: string } }>('/api/battles/:id/winner', async (req, reply) => {
    const parsedId = UuidParam.safeParse(req.params.id);
    if (!parsedId.success) {
      reply.code(400);
      return { error: 'invalid id' };
    }

    const parsed = SetWinnerBody.safeParse(req.body);
    if (!parsed.success) {
      reply.code(400);
      return { error: 'invalid body', details: parsed.error.flatten() };
    }

    const result = await battleRunner.setWinner(parsedId.data, parsed.data.winner_contestant_id);
    if (!result.ok) {
      if (result.notFound) { reply.code(404); return { error: 'battle not found' }; }
      if (result.invalidContestant) { reply.code(422); return { error: 'contestant not found in this battle' }; }
      reply.code(500); return { error: 'unknown error' };
    }
    return { ok: true };
  });

  // GET /api/battles/:id/contestants/:cid/diff — read the diff.patch for a coding contestant.
  app.get<{ Params: { id: string; cid: string } }>('/api/battles/:id/contestants/:cid/diff', async (req, reply) => {
    const parsedId = UuidParam.safeParse(req.params.id);
    const parsedCid = UuidParam.safeParse(req.params.cid);
    if (!parsedId.success || !parsedCid.success) {
      reply.code(400);
      return { error: 'invalid id' };
    }

    const [contestant] = await sql<{ result_path: string | null }[]>`
      SELECT result_path FROM contestants
      WHERE id = ${parsedCid.data} AND battle_id = ${parsedId.data}
    `;
    if (!contestant) {
      reply.code(404);
      return { error: 'contestant not found' };
    }
    if (!contestant.result_path) {
      reply.code(404);
      return { error: 'diff not available' };
    }

    try {
      const text = await readFile(join(contestant.result_path, 'diff.patch'), 'utf8');
      return { diff: text };
    } catch {
      reply.code(404);
      return { error: 'diff not available' };
    }
  });

  // POST /api/battles/:id/cross-examine — start a cross-examination
  app.post<{ Params: { id: string } }>('/api/battles/:id/cross-examine', async (req, reply) => {
    const parsedId = UuidParam.safeParse(req.params.id);
    if (!parsedId.success) {
      reply.code(400);
      return { error: 'invalid id' };
    }
    const id = parsedId.data;

    const parsed = CrossExamineBody.safeParse(req.body);
    if (!parsed.success) {
      reply.code(400);
      return { error: 'invalid body', details: parsed.error.flatten() };
    }

    const [row] = await sql<{ id: string; status: string }[]>`
      SELECT id, status FROM battles WHERE id = ${id}
    `;
    if (!row) {
      reply.code(404);
      return { error: 'battle not found' };
    }
    if (row.status === 'running') {
      reply.code(409);
      return { error: 'battle is still running — cross-examine after all contestants finish' };
    }

    const { crossExamId } = await battleRunner.startCrossExam(id, {
      identity: parsed.data.identity,
      model: parsed.data.model,
    });

    reply.code(202);
    return { cross_exam_id: crossExamId };
  });
}