import test from "node:test";
import assert from "node:assert/strict";
import {
  addBufferToUsage,
  invalidateBufferTokensCache,
  setBufferTokensCache,
} from "../../open-sse/utils/usageTracking.ts";

// ─── Helpers ──────────────────────────────────────────────────────────────

function resetEnv(saved: string | undefined) {
  if (saved === undefined) {
    delete process.env.USAGE_TOKEN_BUFFER;
  } else {
    process.env.USAGE_TOKEN_BUFFER = saved;
  }
}

// ─── addBufferToUsage — baseline / env-var path ───────────────────────────

test("addBufferToUsage — adds DEFAULT 2000 when no env var and cache is null", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  delete process.env.USAGE_TOKEN_BUFFER;
  invalidateBufferTokensCache();

  const result = addBufferToUsage({ prompt_tokens: 25, completion_tokens: 24, total_tokens: 49 });

  // Documents the race: after invalidation the sync path falls back to DEFAULT=2000
  assert.equal(result.prompt_tokens, 2025);
  assert.equal(result.completion_tokens, 24);
  assert.equal(result.total_tokens, 2049);

  resetEnv(saved);
});

test("addBufferToUsage — respects USAGE_TOKEN_BUFFER=0 env override", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  process.env.USAGE_TOKEN_BUFFER = "0";
  invalidateBufferTokensCache();

  const result = addBufferToUsage({ prompt_tokens: 25, completion_tokens: 24, total_tokens: 49 });

  assert.equal(result.prompt_tokens, 25);
  assert.equal(result.total_tokens, 49);

  resetEnv(saved);
});

test("addBufferToUsage — respects USAGE_TOKEN_BUFFER=500 env override", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  process.env.USAGE_TOKEN_BUFFER = "500";
  invalidateBufferTokensCache();

  const result = addBufferToUsage({ prompt_tokens: 86, completion_tokens: 52, total_tokens: 138 });

  assert.equal(result.prompt_tokens, 586);
  assert.equal(result.total_tokens, 638);

  resetEnv(saved);
});

test("addBufferToUsage — also adds to Claude-format input_tokens", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  process.env.USAGE_TOKEN_BUFFER = "100";
  invalidateBufferTokensCache();

  const result = addBufferToUsage({ input_tokens: 40, output_tokens: 20 });

  assert.equal(result.input_tokens, 140);

  resetEnv(saved);
});

test("addBufferToUsage — returns usage unchanged when buffer is 0 via env", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  process.env.USAGE_TOKEN_BUFFER = "0";
  invalidateBufferTokensCache();

  const usage = { prompt_tokens: 86, completion_tokens: 52, total_tokens: 138 };
  const result = addBufferToUsage(usage);

  assert.equal(result.prompt_tokens, 86);
  assert.equal(result.completion_tokens, 52);
  assert.equal(result.total_tokens, 138);

  resetEnv(saved);
});

// ─── setBufferTokensCache — the fix for the race condition ────────────────
//
// The race: invalidateBufferTokensCache() sets _cachedBuffer=null; the next
// synchronous call to getBufferTokens() falls back to DEFAULT=2000 before
// _loadBufferFromDb() (async) completes.
//
// The fix: runtimeSettings.ts calls setBufferTokensCache(newValue) instead of
// invalidateBufferTokensCache() so the correct value is available synchronously.

test("setBufferTokensCache(0) — immediately prevents buffer addition (no race window)", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  delete process.env.USAGE_TOKEN_BUFFER;

  // Simulates what runtimeSettings does after saving usageTokenBuffer=0 in DB
  setBufferTokensCache(0);

  const result = addBufferToUsage({ prompt_tokens: 25, completion_tokens: 24, total_tokens: 49 });

  // With the fix: 0 is applied synchronously — no 2000-token race window
  assert.equal(result.prompt_tokens, 25);
  assert.equal(result.completion_tokens, 24);
  assert.equal(result.total_tokens, 49);

  resetEnv(saved);
  invalidateBufferTokensCache();
});

test("setBufferTokensCache(500) — immediately sets custom buffer value", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  delete process.env.USAGE_TOKEN_BUFFER;

  setBufferTokensCache(500);

  const result = addBufferToUsage({ prompt_tokens: 86, completion_tokens: 52, total_tokens: 138 });

  assert.equal(result.prompt_tokens, 586);
  assert.equal(result.total_tokens, 638);

  resetEnv(saved);
  invalidateBufferTokensCache();
});

test("setBufferTokensCache(0) — works for Claude-format (input_tokens)", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  delete process.env.USAGE_TOKEN_BUFFER;

  setBufferTokensCache(0);

  const result = addBufferToUsage({ input_tokens: 40, output_tokens: 20 });

  assert.equal(result.input_tokens, 40);

  resetEnv(saved);
  invalidateBufferTokensCache();
});

test("invalidateBufferTokensCache — still resets to null (returns DEFAULT on next sync call)", () => {
  const saved = process.env.USAGE_TOKEN_BUFFER;
  delete process.env.USAGE_TOKEN_BUFFER;

  // First prime the cache with a custom value
  setBufferTokensCache(0);
  const afterSet = addBufferToUsage({ prompt_tokens: 10, completion_tokens: 5, total_tokens: 15 });
  assert.equal(afterSet.prompt_tokens, 10); // 0 buffer

  // Then invalidate — next sync call reverts to DEFAULT (2000) while async reload happens
  invalidateBufferTokensCache();
  const afterInvalidate = addBufferToUsage({ prompt_tokens: 10, completion_tokens: 5, total_tokens: 15 });
  assert.equal(afterInvalidate.prompt_tokens, 2010); // DEFAULT=2000 applied (race window)

  resetEnv(saved);
});