#!/usr/bin/env node
'use strict';
const fs = require('node:fs');
const path = require('node:path');
const crypto = require('node:crypto');
const readline = require('node:readline/promises');
const engine = require('./site/engine.js');
const usage = `Usage (Node 20+):
  node cli.cjs annotate SOURCE.jsonl SIDECAR.json [e001=pinned e002=aside ...]
  node cli.cjs export SOURCE.jsonl SIDECAR.json BUDGET_BYTES NEW_OUTPUT_DIR
Outputs: continuation.md + omissions.json. Existing files require interactive confirmation.
Budget includes all Markdown framing; source transcripts are never written.`;
function identity(file) { return path.resolve(file); }
async function confirm(files) {
  if (!files.length) return;
  if (!process.stdin.isTTY) throw Error('Output exists; rerun in a terminal to confirm overwrite');
  const rl = readline.createInterface({input:process.stdin,output:process.stdout});
  try { if (await rl.question('Overwrite ' + files.join(', ') + '? Type OVERWRITE: ') !== 'OVERWRITE') throw Error('Cancelled'); }
  finally { rl.close(); }
}
function guard(file, protectedFiles) {
  if (protectedFiles.includes(identity(file))) throw Error('Output would overwrite an input');
  if (fs.existsSync(file)) {
    const stat = fs.lstatSync(file);
    if (!stat.isFile() || stat.nlink > 1) throw Error('Output must be a regular file with no hard links');
    if (protectedFiles.some(p => fs.existsSync(p) && fs.realpathSync(p) === fs.realpathSync(file))) throw Error('Output aliases an input');
  }
}
async function main() {
  const [command, sourcePath, sidecarPath, ...rest] = process.argv.slice(2);
  if (!['annotate','export'].includes(command) || !sourcePath || !sidecarPath) throw Error(usage);
  const buffer = fs.readFileSync(sourcePath);
  if (buffer.subarray(0,3).equals(Buffer.from([239,187,191]))) throw Error('UTF-8 BOM is unsupported; normalize the export first');
  const source = new TextDecoder('utf-8', {fatal:true}).decode(buffer);
  const exchanges = engine.parse(source);
  const sha256 = crypto.createHash('sha256').update(buffer).digest('hex');
  if (command === 'annotate') {
    guard(sidecarPath, [identity(sourcePath)]);
    const priorities = Object.fromEntries(rest.map(value => {
      const parts = value.split('='); if (parts.length !== 2) throw Error('Use e001=pinned'); return parts;
    }));
    engine.select(exchanges, priorities, Number.MAX_SAFE_INTEGER);
    const existed = fs.existsSync(sidecarPath);
    await confirm(existed?[sidecarPath]:[]);
    fs.writeFileSync(sidecarPath, JSON.stringify({version:1,sourceSha256:sha256,priorities},null,2)+'\n', {flag:existed?'w':'wx',mode:0o600});
    console.log('Sidecar saved; '+exchanges.length+' complete exchanges. Source unchanged.');
  } else {
    if (rest.length !== 2 || !/^\d+$/.test(rest[0])) throw Error(usage);
    const [budget, directory] = rest;
    const sidecar = JSON.parse(fs.readFileSync(sidecarPath,'utf8'));
    if (sidecar.version !== 1 || sidecar.sourceSha256 !== sha256) throw Error('Sidecar does not match this transcript');
    const result = engine.select(exchanges, sidecar.priorities, Number(budget));
    const outputs = ['continuation.md','omissions.json'].map(name => path.join(directory,name));
    for (const file of outputs) guard(file, [identity(sourcePath),identity(sidecarPath)]);
    const existing = new Set(outputs.filter(f => fs.existsSync(f)));
    await confirm([...existing]);
    // Build both artifacts in a private staging directory first. Leave it on publication failure.
    fs.mkdirSync(directory,{recursive:true,mode:0o700});
    const stage = fs.mkdtempSync(path.join(directory,'.context-priority-'));
    fs.writeFileSync(path.join(stage,'continuation.md'),result.packet,{mode:0o600});
    fs.writeFileSync(path.join(stage,'omissions.json'),JSON.stringify({...result.manifest,sourceSha256:sha256},null,2)+'\n',{mode:0o600});
    try {
      for (const file of outputs) {
        guard(file,[identity(sourcePath),identity(sidecarPath)]);
        const staged = path.join(stage,path.basename(file));
        if (existing.has(file)) fs.renameSync(staged,file);
        else { fs.linkSync(staged,file); fs.unlinkSync(staged); }
      }
      fs.rmdirSync(stage);
    } catch (error) { throw Error(error.message+'; recover remaining artifacts from '+stage); }
    console.log('Exported '+result.manifest.packetBytes+'/'+budget+' bytes to '+directory);
  }
}
main().catch(error => { console.error(error.message); process.exitCode = 1; });