/**
 * Phase or milestone completion rollup (`check.completion`).
 *
 * Replaces repeated PLAN/SUMMARY counting and verification checks in
 * `transition.md`, `complete-milestone.md`, `execute-phase.md`.
 * See `.planning/research/decision-routing-audit.md` §3.7.
 */

import { existsSync } from 'node:fs';
import { readFile, readdir } from 'node:fs/promises';
import { join } from 'node:path';
import { GSDError, ErrorClassification } from '../errors.js';
import { normalizePhaseName, planningPaths } from './helpers.js';
import { findPhase } from './phase.js';
import { roadmapAnalyze } from './roadmap.js';
import type { QueryHandler } from './utils.js';

const VALID_SCOPES = new Set(['phase', 'milestone']);

// ─── Helpers ───────────────────────────────────────────────────────────────

function countFailLines(content: string): number {
  return (content.match(/\|\s*FAIL\s*\|/gi) || []).length;
}

async function readFileSafe(filePath: string): Promise<string | null> {
  try {
    return await readFile(filePath, 'utf-8');
  } catch {
    return null;
  }
}

function deriveVerificationStatus(content: string | null): string | null {
  if (!content) return null;
  const failCount = countFailLines(content);
  if (failCount > 0) return 'fail';
  const passMatch = content.match(/\|\s*PASS\s*\|/gi);
  if (passMatch && passMatch.length > 0) return 'pass';
  // Frontmatter status field fallback
  const statusMatch = content.match(/^status:\s*(\S+)/im);
  if (statusMatch) return statusMatch[1].toLowerCase();
  return 'missing';
}

function deriveUatStatus(content: string | null): string | null {
  if (!content) return null;
  const failCount = (content.match(/\|\s*FAIL\s*\|/gi) || []).length;
  if (failCount > 0) return 'fail';
  return 'pass';
}

// ─── Phase scope ───────────────────────────────────────────────────────────

async function checkPhaseCompletion(phaseArg: string, projectDir: string): Promise<Record<string, unknown>> {
  const phaseRes = await findPhase([phaseArg], projectDir);
  const pdata = phaseRes.data as Record<string, unknown>;
  const found = Boolean(pdata.found);

  const plans = (pdata.plans as string[] | undefined) ?? [];
  const summaries = (pdata.summaries as string[] | undefined) ?? [];
  const plans_total = plans.length;

  // Derive which plans are missing a summary
  const summaryIds = new Set(
    summaries
      .map(s => s.replace('-SUMMARY.md', '').replace('SUMMARY.md', ''))
      .filter(Boolean),
  );
  const plans_with_summaries = plans.filter(p => {
    const planId = p.replace('-PLAN.md', '').replace('PLAN.md', '');
    return summaryIds.has(planId);
  }).length;
  const missing_summaries = plans
    .filter(p => {
      const planId = p.replace('-PLAN.md', '').replace('PLAN.md', '');
      return !summaryIds.has(planId);
    });

  // Read VERIFICATION.md and UAT.md if phase was found
  let verificationContent: string | null = null;
  let uatContent: string | null = null;

  if (found && pdata.directory) {
    const phaseDirFull = join(projectDir, pdata.directory as string);
    if (existsSync(phaseDirFull)) {
      try {
        const files = (await readdir(phaseDirFull)).sort((a, b) => a.localeCompare(b));
        const verFile = files.includes('VERIFICATION.md')
          ? 'VERIFICATION.md'
          : files.find(f => f.endsWith('-VERIFICATION.md'));
        const uatFile = files.includes('UAT.md') ? 'UAT.md' : files.find(f => f.endsWith('-UAT.md'));
        if (verFile) verificationContent = await readFileSafe(join(phaseDirFull, verFile));
        if (uatFile) uatContent = await readFileSafe(join(phaseDirFull, uatFile));
      } catch {
        // Phase dir unreadable — treat as no files
      }
    }
  }

  const verification_status = deriveVerificationStatus(verificationContent);
  const uat_status = deriveUatStatus(uatContent);

  const uat_gaps = uatContent ? countFailLines(uatContent) : 0;
  const verification_failures = verificationContent ? countFailLines(verificationContent) : 0;

  const complete =
    plans_total > 0 &&
    missing_summaries.length === 0 &&
    verification_status !== 'fail';

  return {
    complete,
    plans_total,
    plans_with_summaries,
    missing_summaries,
    verification_status,
    uat_status,
    debt: {
      uat_gaps,
      verification_failures,
      human_needed: false,
    },
  };
}

// ─── Milestone scope ───────────────────────────────────────────────────────

async function checkMilestoneCompletion(projectDir: string): Promise<Record<string, unknown>> {
  const analysis = await roadmapAnalyze([], projectDir);
  const adata = analysis.data as { phases?: Array<Record<string, unknown>> };
  const phases = adata.phases ?? [];

  const phase_count = phases.length;
  const completePhases = phases.filter(
    p => p.roadmap_complete === true || p.disk_status === 'complete',
  );
  const phases_complete = completePhases.length;
  const phases_incomplete = phases
    .filter(p => p.roadmap_complete !== true && p.disk_status !== 'complete')
    .map(p => String(normalizePhaseName(String(p.number))));

  const blockers: string[] = [];

  const complete = phase_count > 0 && phases_complete === phase_count;

  return {
    complete,
    phase_count,
    phases_complete,
    phases_incomplete,
    blockers,
  };
}

// ─── Handler ───────────────────────────────────────────────────────────────

export const checkCompletion: QueryHandler = async (args, projectDir) => {
  const scope = args[0];
  if (!scope) {
    throw new GSDError('scope required for check completion (phase|milestone)', ErrorClassification.Validation);
  }
  if (!VALID_SCOPES.has(scope)) {
    throw new GSDError(
      `invalid scope "${scope}" — must be "phase" or "milestone"`,
      ErrorClassification.Validation,
    );
  }

  if (scope === 'phase') {
    const phaseNum = args[1];
    if (!phaseNum) {
      throw new GSDError('phase number required for check completion phase', ErrorClassification.Validation);
    }
    const result = await checkPhaseCompletion(phaseNum, projectDir);
    return { data: result };
  }

  // milestone scope
  const result = await checkMilestoneCompletion(projectDir);
  return { data: result };
};