// Session-grain usage emission (novox/hq ADR 0054). On a schedule, read every transcript under
// `~/.claude/projects/*/<sessionId>.jsonl`, sum its tokens, and emit one session-grain usage event
// per session. The consumer IS the (node,module) session's fixed binding, so no per-message account
// attribution is done — just the totals (port map "don't-map" #3).
//
// Runs as `mesh-tools run` (no broker), so events are emitted best-effort via the sibling mesh-tools
// `emit` primitive; the totals are also written to a file so the reading is observable without one.

import { readdirSync, statSync, readFileSync, writeFileSync, renameSync, mkdirSync } from "node:fs";
import { join, dirname } from "node:path";

import { readSessionFile, type SessionUsage } from "../transcript.js";

/** The vendor-neutral usage row ADR 0054 fixes — the shape the model-usage store upserts. Kept local
 *  to the producer (the normalisation lives in the adapter), so nothing here couples to the SDK. */
interface UsageRow {
  licence: string;
  consumer: string;
  period: string;
  metric: string;
  value: number;
}

/** The licence this session's usage is charged to. The model-access binding names it; failing that,
 *  the deployed env; failing that, "unknown" — a reading is never dropped for want of a licence. */
function boundLicence(): string {
  const bindFile = process.env.MESH_MODEL_ACCESS_BIND_FILE;
  if (bindFile) {
    try {
      const raw = JSON.parse(readFileSync(bindFile, "utf8")) as { licence?: unknown };
      if (typeof raw.licence === "string" && raw.licence) return raw.licence;
    } catch {
      // A missing or unreadable bind file is not fatal — fall through to the env, then to "unknown".
    }
  }
  return process.env.MESH_ANTHROPIC_LICENCE || "unknown";
}

/** Normalise one session reading into ADR 0054 rows: one row per metric, a row omitted when its
 *  number is not finite. `consumer` is node/module/session — the session grain. */
function sessionRows(licence: string, node: string, module: string, r: SessionUsage): UsageRow[] {
  const consumer = `${node}/${module}/${r.sessionId}`;
  const rows: UsageRow[] = [];
  const add = (metric: string, value: number): void => {
    if (Number.isFinite(value)) rows.push({ licence, consumer, period: "session", metric, value });
  };
  add("input_tokens", r.inputTokens);
  add("output_tokens", r.outputTokens);
  add("cache_creation_tokens", r.cacheCreationTokens);
  add("cache_read_tokens", r.cacheReadTokens);
  add("cost_usd", r.costUSD);
  return rows;
}

function projectsDir(): string {
  return process.env.MESH_CLAUDE_PROJECTS_DIR ?? `${process.env.HOME ?? "/root"}/.claude/projects`;
}

/** Every `<sessionId>.jsonl` under the projects tree, with the project directory it sits in. */
function transcripts(root: string): { path: string; sessionId: string }[] {
  const found: { path: string; sessionId: string }[] = [];
  let projects: string[];
  try {
    projects = readdirSync(root);
  } catch {
    return found; // no projects yet is not a failure — there is simply nothing to report.
  }
  for (const proj of projects) {
    const dir = join(root, proj);
    let entries: string[];
    try {
      if (!statSync(dir).isDirectory()) continue;
      entries = readdirSync(dir);
    } catch {
      continue;
    }
    for (const file of entries) {
      if (!file.endsWith(".jsonl")) continue;
      found.push({ path: join(dir, file), sessionId: file.replace(/\.jsonl$/, "") });
    }
  }
  return found;
}

async function main(): Promise<void> {
  const module = process.env.MESH_MODULE ?? "anthropic-consumer";
  const node = process.env.MESH_NODE ?? "unknown";

  const readings: SessionUsage[] = [];
  for (const t of transcripts(projectsDir())) {
    try {
      readings.push(await readSessionFile(t.path, t.sessionId));
    } catch (err) {
      console.error(`[anthropic-consumer] could not read ${t.path}: ${err}`);
    }
  }

  // Emit ADR-0054 rows, not a vendor-shaped body: the consumer of module.*.usage.* is the
  // vendor-neutral model-usage store, so the session→row normalisation is done HERE. The full
  // SessionUsage rides as `raw`, so model, branch, cwd and timestamps are not lost.
  const licence = boundLicence();
  for (const r of readings) {
    await emitUsage({ rows: sessionRows(licence, node, module, r), raw: r });
  }

  if (process.env.MESH_ANTHROPIC_USAGE_OUT) {
    atomicWrite(process.env.MESH_ANTHROPIC_USAGE_OUT, JSON.stringify(readings, null, 2));
  }
  console.error(`[anthropic-consumer] reported ${readings.length} session(s)`);
}

function atomicWrite(path: string, content: string): void {
  mkdirSync(dirname(path), { recursive: true });
  const tmp = `${path}.tmp`;
  writeFileSync(tmp, content, { mode: 0o600 });
  renameSync(tmp, path);
}

/** Emit best-effort via the sibling mesh-tools `emit`, which wires a broker a run step has none. */
async function emitUsage(body: Record<string, unknown>): Promise<void> {
  const main = process.env.MESH_TOOLS_MAIN ?? "/app/dist/main.js";
  const { spawn } = await import("node:child_process");
  await new Promise<void>((resolve) => {
    const child = spawn(
      process.execPath,
      [main, "emit", "usage.session", JSON.stringify(body)],
      { stdio: "inherit" },
    );
    child.on("exit", () => resolve());
    child.on("error", (err) => {
      console.error(`[anthropic-consumer] could not emit usage: ${err}`);
      resolve();
    });
  });
}

await main();