import type { ExtensionAPI } from '@earendil-works/pi-coding-agent';
import * as fs from 'node:fs';
import * as path from 'node:path';
import { execSync } from 'node:child_process';

function readJsonIfExists<T = unknown>(filePath: string): T | undefined {
  try {
    const raw = fs.readFileSync(filePath, 'utf8');
    return JSON.parse(raw) as T;
  } catch {
    return undefined;
  }
}

function isAutoUpdateEnabled(projectDir: string): boolean {
  for (const dirName of ['.ua', '.understand-anything']) {
    const configPath = path.join(projectDir, dirName, 'config.json');
    const config = readJsonIfExists<{ autoUpdate?: boolean }>(configPath);
    if (config?.autoUpdate === true) return true;
  }
  return false;
}

function hasKnowledgeGraph(projectDir: string): boolean {
  for (const dirName of ['.ua', '.understand-anything']) {
    if (fs.existsSync(path.join(projectDir, dirName, 'knowledge-graph.json'))) {
      return true;
    }
  }
  return false;
}

function getCurrentCommit(cwd: string): string | undefined {
  try {
    return execSync('git rev-parse HEAD', { cwd, encoding: 'utf8' }).trim();
  } catch {
    return undefined;
  }
}

function getGraphCommit(projectDir: string): string | undefined {
  for (const dirName of ['.ua', '.understand-anything']) {
    const metaPath = path.join(projectDir, dirName, 'meta.json');
    const meta = readJsonIfExists<{ gitCommitHash?: string }>(metaPath);
    if (meta?.gitCommitHash) return meta.gitCommitHash;
  }
  return undefined;
}

function isGitMutation(cmd: string): boolean {
  return /git\s+(commit|merge|cherry-pick|rebase)/.test(cmd);
}

export default function autoUpdateHook(pi: ExtensionAPI): void {
  // On bash tool result, detect git mutations and prompt for an update.
  pi.on('tool_result', async (event, ctx) => {
    if (event.toolName !== 'bash') return;
    const cmd = String(event.input?.command ?? '');
    if (!isGitMutation(cmd)) return;

    const projectDir = ctx.cwd;
    if (!isAutoUpdateEnabled(projectDir)) return;
    if (!hasKnowledgeGraph(projectDir)) return;

    const message = '[understand-anything] Git mutation detected with auto-update enabled. Run /understand to update the knowledge graph.';
    if (ctx.ui) {
      ctx.ui.setStatus('understand-anything', message);
    }
  });

  // On user bash (!/!!), detect git mutations and prompt for an update.
  pi.on('user_bash', async (event, ctx) => {
    if (!isGitMutation(event.command)) return;

    const projectDir = ctx.cwd;
    if (!isAutoUpdateEnabled(projectDir)) return;
    if (!hasKnowledgeGraph(projectDir)) return;

    const message = '[understand-anything] Git mutation detected with auto-update enabled. Run /understand to update the knowledge graph.';
    if (ctx.ui) {
      ctx.ui.setStatus('understand-anything', message);
    }
  });

  // On session start, check whether the graph is stale and notify the user.
  pi.on('session_start', async (event, ctx) => {
    const projectDir = ctx.cwd;
    if (!isAutoUpdateEnabled(projectDir)) return;
    if (!hasKnowledgeGraph(projectDir)) return;

    const graphCommit = getGraphCommit(projectDir);
    const currentCommit = getCurrentCommit(projectDir);
    if (!graphCommit || !currentCommit || graphCommit === currentCommit) return;

    const message = '[understand-anything] Knowledge graph is stale. Run /understand to update it.';
    if (ctx.ui) {
      ctx.ui.setStatus('understand-anything', message);
    }
  });
}