// Claude usage snapshot (POST /claude-usage, GET /claude-usage), contract
// `schemaVersion: 1`, shared with the ThinkPad agent and the admin dashboard.
//
// Pure module: no I/O, no config, no side effects. index.js wires the routes
// and owns the file; the workstation agent can test its own snapshot against
// this very sanitizer before it ever sends it.
//
// Whitelist rebuild, field by field. The stored object is read back by GET
// /claude-usage and ends up in the admin dashboard's React tree, so nothing
// from the payload is kept verbatim:
//   - an unknown field is dropped;
//   - an invalid value is dropped (the key is left out), never coerced. That
//     covers a negative number, a number past 2^53, a `detail` outside its
//     regex and a `status` outside its enum;
//   - a list past its bound keeps its first entries (`days` keeps its LAST
//     ones: the contract orders them oldest first, so today survives);
//   - strings are truncated to 128 characters, not filtered: safety rests on
//     the consumer escaping at render time, as for the host snapshots.
// Only two things refuse the whole body: a body that is not a JSON object, and
// a `schemaVersion` other than 1 (a future contract must not be silently
// reshaped into this one).

const SCHEMA_VERSION = 1;

// Worst case within the bounds below is about 46 KB, hence 64 KiB and not 32.
const CLAUDE_USAGE_MAX_BODY_BYTES = 65536;

const MAX_DAYS = 31;
const MAX_MODELS_PER_DAY = 12;
const MAX_LIMIT_ITEMS = 12;
const MAX_PROJECTS = 9;
const MAX_STRING_LENGTH = 128;

const LIMIT_STATUSES = ["ok", "token_expired", "http_error", "unavailable", "disabled"];
const DAY_DATE_RE = /^\d{4}-\d{2}-\d{2}$/;
const MODEL_KEY_RE = /^[a-z0-9][a-z0-9.\-]{0,63}$/;
// A machine-readable reason code, never free text: a free-form detail could
// carry an upstream response body all the way to the dashboard.
const DETAIL_RE = /^[a-z0-9_]{1,32}$/;
// Full ISO 8601 timestamp with an explicit offset, as Date#toISOString() and
// the upstream API write them.
const ISO_TIMESTAMP_RE = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d{1,9})?(Z|[+-]\d{2}:\d{2})$/;

const MODEL_COUNTERS = ["input", "output", "cacheCreation", "cacheRead", "requests"];
const PROJECT_COUNTERS = ["work", "cacheRead", "requests"];

function isPlainObject(value) {
  return typeof value === "object" && value !== null && !Array.isArray(value);
}

function cleanString(value) {
  if (typeof value !== "string") return undefined;
  return value.slice(0, MAX_STRING_LENGTH);
}

function cleanCount(value) {
  return Number.isSafeInteger(value) && value >= 0 ? value : undefined;
}

function cleanPercent(value) {
  const count = cleanCount(value);
  return count !== undefined && count <= 100 ? count : undefined;
}

function cleanTimestamp(value) {
  if (typeof value !== "string" || value.length > MAX_STRING_LENGTH) return undefined;
  if (!ISO_TIMESTAMP_RE.test(value) || Number.isNaN(Date.parse(value))) return undefined;
  return value;
}

// Also used by index.js on the stored receivedAt of both snapshot files: the
// server only ever stamps Date#toISOString(), and new Date() alone would
// accept "1" or a bare date (#54).
function isIsoTimestamp(value) {
  return cleanTimestamp(value) !== undefined;
}

// The calendar check catches what the regex lets through (2026-02-31).
function cleanDayDate(value) {
  if (typeof value !== "string" || !DAY_DATE_RE.test(value)) return undefined;
  const parsed = new Date(`${value}T00:00:00Z`);
  if (Number.isNaN(parsed.getTime()) || parsed.toISOString().slice(0, 10) !== value) return undefined;
  return value;
}

// Copy `key` into `out` only when the cleaner kept a value.
function put(out, key, value) {
  if (value !== undefined) out[key] = value;
}

// `null` is a legitimate value for the fields the contract declares nullable.
function putNullable(out, key, raw, clean) {
  if (raw === null) out[key] = null;
  else put(out, key, clean(raw));
}

function sanitizeCounters(value, keys) {
  const out = {};
  for (const key of keys) put(out, key, cleanCount(value[key]));
  return out;
}

function sanitizeModels(value) {
  if (!isPlainObject(value)) return undefined;
  const out = {};
  let kept = 0;
  for (const key of Object.keys(value)) {
    if (kept >= MAX_MODELS_PER_DAY) break;
    if (!MODEL_KEY_RE.test(key) || !isPlainObject(value[key])) continue;
    out[key] = sanitizeCounters(value[key], MODEL_COUNTERS);
    kept += 1;
  }
  return out;
}

function sanitizeDays(value) {
  if (!Array.isArray(value)) return undefined;
  const days = [];
  for (const entry of value) {
    if (!isPlainObject(entry)) continue;
    const date = cleanDayDate(entry.date);
    if (date === undefined) continue;
    const day = { date };
    put(day, "models", sanitizeModels(entry.models));
    days.push(day);
  }
  return days.slice(-MAX_DAYS);
}

function sanitizeLimitItem(value) {
  const item = {};
  put(item, "kind", cleanString(value.kind));
  put(item, "group", cleanString(value.group));
  put(item, "percent", cleanPercent(value.percent));
  put(item, "severity", cleanString(value.severity));
  putNullable(item, "resetsAt", value.resetsAt, cleanTimestamp);
  putNullable(item, "model", value.model, cleanString);
  return item;
}

function sanitizeLimits(value) {
  if (!isPlainObject(value)) return undefined;
  const limits = {};
  put(limits, "status", LIMIT_STATUSES.includes(value.status) ? value.status : undefined);
  put(limits, "detail", typeof value.detail === "string" && DETAIL_RE.test(value.detail) ? value.detail : undefined);
  putNullable(limits, "fetchedAt", value.fetchedAt, cleanTimestamp);
  if (Array.isArray(value.items)) {
    limits.items = value.items.filter(isPlainObject).slice(0, MAX_LIMIT_ITEMS).map(sanitizeLimitItem);
  }
  return limits;
}

function sanitizeProjects(value) {
  if (!Array.isArray(value)) return undefined;
  return value
    .filter(isPlainObject)
    .slice(0, MAX_PROJECTS)
    .map((entry) => {
      const project = {};
      put(project, "name", cleanString(entry.name));
      Object.assign(project, sanitizeCounters(entry, PROJECT_COUNTERS));
      return project;
    });
}

// Returns { snapshot } or { error }. Idempotent: a sanitized snapshot comes
// back unchanged, which is what lets GET re-run it on the stored file.
function sanitizeClaudeUsage(payload) {
  if (!isPlainObject(payload)) return { error: "body must be a JSON object" };
  if (payload.schemaVersion !== SCHEMA_VERSION) {
    return { error: `schemaVersion must be ${SCHEMA_VERSION}` };
  }

  const snapshot = { schemaVersion: SCHEMA_VERSION };
  put(snapshot, "generatedAt", cleanTimestamp(payload.generatedAt));
  put(snapshot, "claudeCodeVersion", cleanString(payload.claudeCodeVersion));
  put(snapshot, "timeZone", cleanString(payload.timeZone));
  put(snapshot, "limits", sanitizeLimits(payload.limits));
  put(snapshot, "days", sanitizeDays(payload.days));
  put(snapshot, "projects", sanitizeProjects(payload.projects));
  return { snapshot };
}

module.exports = {
  sanitizeClaudeUsage,
  isIsoTimestamp,
  CLAUDE_USAGE_MAX_BODY_BYTES,
  SCHEMA_VERSION,
  MAX_DAYS,
  MAX_MODELS_PER_DAY,
  MAX_LIMIT_ITEMS,
  MAX_PROJECTS,
  MAX_STRING_LENGTH,
  LIMIT_STATUSES,
};