/**
 * The auto-updater's state on this machine (scripts/update-check.mjs), for
 * the master: its last check, an update that failed and waits to retry, how
 * far the checkout is behind origin, and tracked files edited by hand — which
 * stop the fast-forward pull. Read from the files the updater keeps and from
 * git, and cached: the reporter asks every 30 seconds.
 */

import { execFileSync } from 'node:child_process';
import { readFileSync } from 'node:fs';
import path from 'node:path';
import type { UpdaterStatus } from './master-protocol';

const CACHE_MS = 2 * 60_000;
const BRANCH = process.env.AUTOFIRMER_BRANCH ?? 'master';

// Per process: instrumentation.ts and the route handlers each load this module.
const g = globalThis as typeof globalThis & { __updaterStatus?: { at: number; status: UpdaterStatus } };

function readScript(file: string): string | null {
    try {
        return readFileSync(path.join(process.cwd(), 'scripts', file), 'utf8');
    } catch {
        return null;
    }
}

function git(args: string[]): string | null {
    try {
        return execFileSync('git', args, {
            cwd: process.cwd(),
            encoding: 'utf8',
            stdio: ['ignore', 'pipe', 'ignore'],
            timeout: 5_000,
        }).trimEnd();
    } catch {
        return null;
    }
}

function readFailure(): UpdaterStatus['failed'] {
    try {
        const f = JSON.parse(readScript('.update-failed') ?? 'null') as Record<string, unknown> | null;
        if (!f || typeof f.target !== 'string') return null;
        const at = Number(f.at);
        return {
            target: f.target.slice(0, 12),
            step: String(f.step ?? '').slice(0, 40),
            at: Number.isFinite(at) ? new Date(at).toISOString() : '',
            attempts: Number(f.count) || 1,
        };
    } catch {
        return null;
    }
}

export function updaterStatus(now = Date.now()): UpdaterStatus {
    const cached = g.__updaterStatus;
    if (cached && now - cached.at < CACHE_MS) return cached.status;

    // "<ISO time>  <status>", rewritten on every check.
    const last = /^(\S+)\s+(.*)$/.exec(readScript('.last-check')?.trim() ?? '');
    const behind = git(['rev-list', '--count', `HEAD..origin/${BRANCH}`]);
    const changed = git(['status', '--porcelain', '--untracked-files=no']);
    const status: UpdaterStatus = {
        lastCheckAt: last ? last[1] : null,
        lastCheck: last ? last[2].slice(0, 200) : null,
        failed: readFailure(),
        builtCommit: readScript('.built-commit')?.trim().slice(0, 12) || null,
        behind: behind !== null && /^\d+$/.test(behind) ? Number(behind) : null,
        // "XY path" per line; the status column can start with a space.
        localChanges: changed
            ? changed.split('\n').map((line) => line.slice(3).trim()).filter(Boolean).slice(0, 10)
            : [],
    };
    g.__updaterStatus = { at: now, status };
    return status;
}