import test from "node:test";
import assert from "node:assert/strict";
import fs from "node:fs";
import os from "node:os";
import path from "node:path";

const previousDataDir = process.env.DATA_DIR;
const previousDisableSqliteAutoBackup = process.env.DISABLE_SQLITE_AUTO_BACKUP;
const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-emergency-fallback-"));
process.env.DATA_DIR = tmpDir;
process.env.DISABLE_SQLITE_AUTO_BACKUP = "true";

const core = await import("../../../src/lib/db/core.ts");
const { setFeatureFlagOverride, removeFeatureFlagOverride } =
  await import("../../../src/lib/db/featureFlags.ts");
const {
  shouldUseFallback,
  isEmergencyFallbackEnvEnabled,
  EMERGENCY_FALLBACK_CONFIG,
  resetEmergencyFallbackEnvCache,
  setEmergencyFallbackFeatureFlagResolverForTest,
} = await import("../../../open-sse/services/emergencyFallback.ts");

function restoreEnv(name: string, value: string | undefined) {
  if (value === undefined) {
    delete process.env[name];
  } else {
    process.env[name] = value;
  }
}

function resetTestState() {
  core.resetDbInstance();
  fs.rmSync(tmpDir, { recursive: true, force: true });
  fs.mkdirSync(tmpDir, { recursive: true });
  delete process.env.OMNIROUTE_EMERGENCY_FALLBACK;
  resetEmergencyFallbackEnvCache();
  setEmergencyFallbackFeatureFlagResolverForTest(null);
}

test.beforeEach(() => {
  resetTestState();
});

test.afterEach(() => {
  resetEmergencyFallbackEnvCache();
  setEmergencyFallbackFeatureFlagResolverForTest(null);
  delete process.env.OMNIROUTE_EMERGENCY_FALLBACK;
});

test.after(() => {
  core.resetDbInstance();
  fs.rmSync(tmpDir, { recursive: true, force: true });
  restoreEnv("DATA_DIR", previousDataDir);
  restoreEnv("DISABLE_SQLITE_AUTO_BACKUP", previousDisableSqliteAutoBackup);
});

function withEnv(value: string | undefined, fn: () => void) {
  const previous = process.env.OMNIROUTE_EMERGENCY_FALLBACK;
  if (value === undefined) {
    delete process.env.OMNIROUTE_EMERGENCY_FALLBACK;
  } else {
    process.env.OMNIROUTE_EMERGENCY_FALLBACK = value;
  }
  resetEmergencyFallbackEnvCache();
  try {
    fn();
  } finally {
    restoreEnv("OMNIROUTE_EMERGENCY_FALLBACK", previous);
    resetEmergencyFallbackEnvCache();
  }
}

function withFeatureFlagOverride(value: string, fn: () => void) {
  try {
    setFeatureFlagOverride("OMNIROUTE_EMERGENCY_FALLBACK", value);
    resetEmergencyFallbackEnvCache();
    fn();
  } finally {
    removeFeatureFlagOverride("OMNIROUTE_EMERGENCY_FALLBACK");
    resetEmergencyFallbackEnvCache();
  }
}

test("emergency fallback stays enabled when the env switch is unset (default behavior)", () => {
  withEnv(undefined, () => {
    assert.equal(isEmergencyFallbackEnvEnabled(), true);
    const decision = shouldUseFallback(402, "", false);
    assert.equal(decision.shouldFallback, true);
    if (decision.shouldFallback) {
      assert.equal(decision.provider, EMERGENCY_FALLBACK_CONFIG.provider);
      assert.equal(decision.model, EMERGENCY_FALLBACK_CONFIG.model);
    }
  });
});

test("budget keywords trigger fallback when the env switch is unset", () => {
  withEnv(undefined, () => {
    const decision = shouldUseFallback(429, "All accounts quota exceeded", false);
    assert.equal(decision.shouldFallback, true);
  });
});

test("OMNIROUTE_EMERGENCY_FALLBACK=false disables the 402 redirect", () => {
  withEnv("false", () => {
    assert.equal(isEmergencyFallbackEnvEnabled(), false);
    const decision = shouldUseFallback(402, "", false);
    assert.equal(decision.shouldFallback, false);
    assert.match(decision.reason, /OMNIROUTE_EMERGENCY_FALLBACK/);
  });
});

test("OMNIROUTE_EMERGENCY_FALLBACK=0 disables the budget-keyword redirect", () => {
  withEnv("0", () => {
    const decision = shouldUseFallback(429, "quota exceeded for account", false);
    assert.equal(decision.shouldFallback, false);
    assert.match(decision.reason, /OMNIROUTE_EMERGENCY_FALLBACK/);
  });
});

test("DB feature flag override can disable an env-enabled fallback", () => {
  withEnv("true", () => {
    withFeatureFlagOverride("false", () => {
      const decision = shouldUseFallback(402, "", false);
      assert.equal(isEmergencyFallbackEnvEnabled(), false);
      assert.equal(decision.shouldFallback, false);
      assert.match(decision.reason, /OMNIROUTE_EMERGENCY_FALLBACK/);
    });
  });
});

test("DB feature flag override can enable an env-disabled fallback", () => {
  withEnv("false", () => {
    withFeatureFlagOverride("true", () => {
      const decision = shouldUseFallback(402, "", false);
      assert.equal(isEmergencyFallbackEnvEnabled(), true);
      assert.equal(decision.shouldFallback, true);
    });
  });
});

test("raw env fallback is used when feature flag resolution throws", () => {
  withEnv("0", () => {
    const warnings: unknown[][] = [];
    const previousWarn = console.warn;
    console.warn = (...args: unknown[]) => {
      warnings.push(args);
    };
    setEmergencyFallbackFeatureFlagResolverForTest(() => {
      throw new Error("feature flag store unavailable");
    });

    try {
      assert.equal(isEmergencyFallbackEnvEnabled(), false);
      const decision = shouldUseFallback(402, "", false);
      assert.equal(decision.shouldFallback, false);
      assert.match(decision.reason, /OMNIROUTE_EMERGENCY_FALLBACK/);
      assert.equal(warnings.length, 1);
      assert.match(String(warnings[0]?.[0]), /Feature flag resolution failed/);
    } finally {
      console.warn = previousWarn;
    }
  });
});

test("explicit truthy values keep the fallback enabled", () => {
  withEnv("true", () => {
    assert.equal(isEmergencyFallbackEnvEnabled(), true);
    assert.equal(shouldUseFallback(402, "", false).shouldFallback, true);
  });
});

test("env switch does not override config.enabled=false", () => {
  withEnv("true", () => {
    const decision = shouldUseFallback(402, "", false, {
      ...EMERGENCY_FALLBACK_CONFIG,
      enabled: false,
    });
    assert.equal(decision.shouldFallback, false);
  });
});

test("tool-bearing requests are still skipped regardless of env switch", () => {
  withEnv(undefined, () => {
    const decision = shouldUseFallback(402, "", true);
    assert.equal(decision.shouldFallback, false);
    assert.match(decision.reason, /tools/);
  });
});