#!/usr/bin/env node

// claude-usage agent entry point (issue #50). Runs from the ThinkPad's
// crontab every 15 minutes through run-claude-usage.sh:
//
//   1. aggregate the local transcripts (aggregate.js), frozen days excluded;
//   2. read the plan limits once (limits.js);
//   3. update and write the local cache (state.js) BEFORE pushing, so a failed
//      push never costs the next beat a full rescan;
//   4. assemble the schemaVersion 1 snapshot, measure it, push it once.
//
// Zero runtime dependencies (Node 22 global fetch). Same two rules as
// agent/push-metrics.js, for the same reason — the output goes to
// `logger -t claude-usage`, so into syslog and journald for good:
//
//   * NO QUEUE, NO REPLAY. One beat = one attempt; a failure exits non-zero.
//   * THE OUTPUT NEVER CARRIES A SECRET. Neither the ingest token nor the
//     OAuth token is printed. Failures are rebuilt from fixed templates plus an
//     HTTP status or a sanitized error code — never an error object, a message
//     from the HTTP stack (undici quotes an invalid header value in it), the
//     request options or a response body.

const os = require("node:os");
const path = require("node:path");

const { aggregate, torontoDay, TIME_ZONE } = require("./aggregate.js");
const { fetchLimits, defaultCredentialsPath } = require("./limits.js");
const {
  loadState,
  saveState,
  nextState,
  limitsForSnapshot,
  defaultStateDir,
  stateFilePath,
} = require("./state.js");

const SCHEMA_VERSION = 1;
// Same ceiling as the server (CLAUDE_USAGE_MAX_BODY_BYTES): a larger body
// would be refused with a 413, so it is not even sent.
const MAX_BODY_BYTES = 65536;
const PUSH_TIMEOUT_MS = 10000;

const EXIT_OK = 0;
const EXIT_CONFIG = 1;
const EXIT_PUSH = 2;

const PREFIX = "claude-usage:";

// A token is printable ASCII without spaces. Checked up front: fetch rejects
// an invalid header value with a message that QUOTES it.
const TOKEN_RE = /^[\x21-\x7e]+$/;
// What may be printed of an error: a system or undici code (ECONNREFUSED,
// UND_ERR_CONNECT_TIMEOUT: upper case only) or an error class name
// (TimeoutError, TypeError). Anything else, whatever field it came from, is
// replaced by UNKNOWN rather than trusted.
const ERROR_CODE_RE = /^[A-Z][A-Z0-9_]{1,39}$/;
const ERROR_NAME_RE = /^[A-Z][A-Za-z]{0,30}Error$/;

function safeCode(err) {
  const codes = [err && err.cause && err.cause.code, err && err.code];
  for (const c of codes) {
    if (typeof c === "string" && ERROR_CODE_RE.test(c)) return c;
  }
  const name = err && err.name;
  return typeof name === "string" && ERROR_NAME_RE.test(name) ? name : "UNKNOWN";
}

function readConfig(env) {
  const apiUrl = String(env.CLAUDE_USAGE_API_URL || "").trim();
  const token = env.CLAUDE_USAGE_INGEST_TOKEN || "";
  if (!apiUrl) return { error: "CLAUDE_USAGE_API_URL is not set" };
  if (!token) return { error: "CLAUDE_USAGE_INGEST_TOKEN is not set" };
  if (!TOKEN_RE.test(token)) {
    return {
      error:
        "CLAUDE_USAGE_INGEST_TOKEN contains an invalid character (a trailing newline or space in the env file is the usual cause)",
    };
  }
  let target;
  try {
    target = new URL(`${apiUrl.replace(/\/+$/, "")}/claude-usage`);
  } catch {
    return { error: "CLAUDE_USAGE_API_URL is not a valid URL" };
  }
  // The ingest token travels in this request: https only, no exception.
  if (target.protocol !== "https:") return { error: "CLAUDE_USAGE_API_URL must be https://" };
  return { config: { target: target.href, token } };
}

function buildSnapshot({ now, aggregated, limits }) {
  const snapshot = {
    schemaVersion: SCHEMA_VERSION,
    generatedAt: new Date(now).toISOString(),
  };
  // Left out rather than null: the contract types it as a string, and the
  // server drops a null there anyway.
  if (aggregated.claudeCodeVersion) snapshot.claudeCodeVersion = aggregated.claudeCodeVersion;
  snapshot.timeZone = TIME_ZONE;
  snapshot.limits = limits;
  snapshot.days = aggregated.days;
  snapshot.projects = aggregated.projects;
  return snapshot;
}

async function pushSnapshot({ target, token, body, fetchImpl }) {
  let res;
  try {
    res = await fetchImpl(target, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        Authorization: `Bearer ${token}`,
      },
      body,
      redirect: "error",
      signal: AbortSignal.timeout(PUSH_TIMEOUT_MS),
    });
  } catch (err) {
    return { error: `push failed: request error (code=${safeCode(err)})` };
  }
  // The response body is never read, never logged.
  try {
    if (res.body && typeof res.body.cancel === "function") res.body.cancel().catch(() => {});
  } catch {
    // nothing to release
  }
  const status = Number.isInteger(res.status) ? res.status : 0;
  if (status >= 200 && status <= 299) return { status };
  return { error: `push failed: HTTP ${status}` };
}

/**
 * @param {string[]} argv
 * @param {object}   env
 * @param {object}   deps  injectable for tests: home, fetch, now, readFile, openFile, log, logError
 * @returns {Promise<number>} exit code
 */
async function main(argv = process.argv.slice(2), env = process.env, deps = {}) {
  const home = deps.home || os.homedir();
  const fetchImpl = deps.fetch || globalThis.fetch;
  const now = deps.now !== undefined ? deps.now : Date.now();
  const log = deps.log || ((line) => console.log(line));
  const logError = deps.logError || ((line) => console.error(line));

  const dryRun = argv.includes("--dry-run");

  // Configuration first: a full scan costs seconds, no point spending them to
  // then discover a typo in the env file. A dry run needs no configuration.
  let config = null;
  if (!dryRun) {
    const result = readConfig(env);
    if (result.error) {
      logError(`${PREFIX} configuration error: ${result.error}`);
      return EXIT_CONFIG;
    }
    config = result.config;
  }

  const stateFile = stateFilePath(deps.stateDir || defaultStateDir(home));
  const state = loadState(stateFile);
  const today = torontoDay(now);

  const aggregated = await aggregate({
    root: deps.transcriptsRoot || path.join(home, ".claude", "projects"),
    frozenDays: state.frozenDays,
    today,
    homedir: home,
    ...(deps.openFile ? { openFile: deps.openFile } : {}),
  });

  const limits = await fetchLimits({
    env,
    credentialsPath: deps.credentialsPath || defaultCredentialsPath(home),
    ...(deps.readFile ? { readFile: deps.readFile } : {}),
    fetch: fetchImpl,
    claudeCodeVersion: aggregated.claudeCodeVersion,
    now,
  });

  // An incomplete scan freezes nothing. Only a count is printed: a path
  // would put a project name in syslog for good.
  const complete = aggregated.readErrors === 0;
  if (!complete) {
    logError(`${PREFIX} warning: read_errors=${aggregated.readErrors}, no day frozen this beat`);
  }
  const updated = nextState(state, { openDays: aggregated.openDays, today, limits, freeze: complete });
  // Cache first. A dry run is read-only: it shows what would be sent and
  // leaves the cache exactly as the cron left it.
  if (!dryRun) {
    try {
      saveState(stateFile, updated);
    } catch (err) {
      // Not fatal: the next beat rescans, which is slow but correct.
      logError(`${PREFIX} warning: state not saved (code=${safeCode(err)})`);
    }
  }

  const snapshot = buildSnapshot({ now, aggregated, limits: limitsForSnapshot(limits, updated) });
  const body = JSON.stringify(snapshot);
  const bytes = Buffer.byteLength(body, "utf-8");

  if (dryRun) log(JSON.stringify(snapshot, null, 2));

  if (bytes > MAX_BODY_BYTES) {
    logError(`${PREFIX} payload_too_large bytes=${bytes} max=${MAX_BODY_BYTES}`);
    return EXIT_PUSH;
  }
  if (dryRun) return EXIT_OK;

  const pushed = await pushSnapshot({ target: config.target, token: config.token, body, fetchImpl });
  const summary = `limits=${snapshot.limits.status}${snapshot.limits.detail ? ` detail=${snapshot.limits.detail}` : ""} bytes=${bytes}`;
  if (pushed.error) {
    logError(`${PREFIX} ${pushed.error} ${summary}`);
    return EXIT_PUSH;
  }
  log(`${PREFIX} ok status=${pushed.status} ${summary}`);
  return EXIT_OK;
}

if (require.main === module) {
  main().then(
    (code) => {
      process.exitCode = code;
    },
    (err) => {
      // Nothing should land here. The code only, never the object or its
      // message: either could carry a request option.
      console.error(`${PREFIX} unexpected failure (code=${safeCode(err)})`);
      process.exitCode = EXIT_PUSH;
    },
  );
}

module.exports = {
  main,
  readConfig,
  buildSnapshot,
  pushSnapshot,
  MAX_BODY_BYTES,
  PUSH_TIMEOUT_MS,
  EXIT_OK,
  EXIT_CONFIG,
  EXIT_PUSH,
};