/**
 * Field-Level Encryption — AES-256-GCM
 *
 * Encrypts/decrypts sensitive fields (API keys, tokens) stored in SQLite.
 * Format: `enc:v1:<iv_hex>:<ciphertext_hex>:<authTag_hex>`
 *
 * If STORAGE_ENCRYPTION_KEY is not set, operates in passthrough mode
 * (stores plaintext for development convenience).
 *
 * KEY DERIVATION CHANGE (v3.7.9):
 * The PRIMARY key is now derived with a static salt ("omniroute-field-encryption-v1").
 * The LEGACY key used a dynamic salt (sha256 hash of the key). Auto-migration
 * re-encrypts any legacy-encrypted tokens on decrypt.
 *
 * Why the change?
 * The dynamic salt `createHash("sha256").update(secret).digest().slice(0, 16)` produced
 * a different derived key than the static salt `"omniroute-field-encryption-v1"`. When the
 * health-check/token-refresh path used one derivation and the main API used another,
 * tokens encrypted by one path became undecryptable by the other, causing:
 * - Persistent decrypt failures
 * - Re-encryption loops (health-check undoing fixes)
 * - CPU spikes (50%) from error cascades
 *
 * This fix makes the static salt the primary derivation and auto-migrates
 * legacy-encrypted tokens back to static-salt encryption.
 */

import { createCipheriv, createDecipheriv, randomBytes, scryptSync, createHash } from "crypto";

const ALGORITHM = "aes-256-gcm";
const IV_LENGTH = 16;
const KEY_LENGTH = 32;
/**
 * GCM authentication tag length, in bytes. Pinned to the full 16-byte tag
 * produced by `cipher.getAuthTag()`. Passing `authTagLength` to
 * `createDecipheriv` rejects truncated authentication tags up front, closing
 * the GCM tag-truncation forgery vector (Semgrep gcm-no-tag-length).
 */
const AUTH_TAG_LENGTH = 16;
const PREFIX = "enc:v1:";
const STATIC_SALT = "omniroute-field-encryption-v1";

let _staticKey: Buffer | null = null;
let _legacyDynamicKey: Buffer | null = null;
/** Connection object with potentially encrypted credential fields. */
export interface ConnectionFields {
  apiKey?: string | null;
  accessToken?: string | null;
  refreshToken?: string | null;
  idToken?: string | null;
  [key: string]: unknown;
}

/**
 * #9927 — dedupe tracker for credential-decrypt-failure messages. The health
 * sweep / refresh / request routing re-decrypt the same corrupt row every
 * cycle; we log the enriched, actionable message ONCE per
 * (provider + connection + failing-ciphertext) state so it does not spam
 * every sweep, while still re-logging if the row state actually changes
 * (e.g. a different field starts failing) instead of permanently suppressing.
 */
const loggedDecryptFailures = new Set<string>();

function decryptFailureSignature(
  connectionId: string,
  provider: string,
  failed: Array<{ field: string; value: unknown }>
): string {
  const parts = failed
    .map((f) => `${f.field}:${typeof f.value === "string" ? f.value : ""}`)
    .sort()
    .join("|");
  return `${provider}::${connectionId}::${parts}`;
}

const RECOVERY_HINT =
  "Re-authenticate this account, or verify STORAGE_ENCRYPTION_KEY matches the key used to store it.";

/**
 * Derive the PRIMARY encryption key using the static salt.
 * This is the canonical key derivation that all new encryptions use.
 * Returns null if no encryption key is configured.
 */
function getStaticKey(): Buffer | null {
  if (_staticKey !== null) return _staticKey;

  const secret = process.env.STORAGE_ENCRYPTION_KEY;
  if (!secret || typeof secret !== "string" || secret.trim().length === 0) return null;

  try {
    _staticKey = scryptSync(secret, STATIC_SALT, KEY_LENGTH);
  } catch (err: unknown) {
    const message = err instanceof Error ? err.message : String(err);
    console.error(
      `[Encryption] Failed to derive key from STORAGE_ENCRYPTION_KEY: ${message}. ` +
        `Generate a valid key with: openssl rand -base64 32`
    );
    return null;
  }
  return _staticKey;
}

/**
 * Derive the LEGACY key using the old dynamic salt method.
 * Used exclusively for fallback decryption of tokens encrypted by older versions.
 *
 * The old dynamic salt was: createHash("sha256").update(secret).digest().slice(0, 16)
 * This produced a different derived key than the static salt, causing incompatibility.
 */
function getLegacyDynamicKey(): Buffer | null {
  if (_legacyDynamicKey !== null) return _legacyDynamicKey;

  const secret = process.env.STORAGE_ENCRYPTION_KEY;
  if (!secret || typeof secret !== "string" || secret.trim().length === 0) return null;

  const dynamicSalt = createHash("sha256").update(secret).digest().slice(0, 16);
  try {
    _legacyDynamicKey = scryptSync(secret, dynamicSalt, KEY_LENGTH);
  } catch {
    return null;
  }
  return _legacyDynamicKey;
}

/** Check if encryption is enabled. */
export function isEncryptionEnabled(): boolean {
  return !!process.env.STORAGE_ENCRYPTION_KEY;
}

/**
 * True when `value` is a stored ciphertext (carries the `enc:v1:` prefix).
 * Lets callers tell "credential present but undecryptable" (stale/changed
 * STORAGE_ENCRYPTION_KEY) apart from "credential genuinely empty" — decrypt()
 * collapses both to null otherwise. See #6148.
 */
export function looksEncrypted(value: unknown): boolean {
  return typeof value === "string" && value.startsWith(PREFIX);
}

/**
 * Encrypt a plaintext string using the STATIC salt key.
 * If encryption is not configured, returns plaintext unchanged.
 */
export function encrypt(plaintext: string | null | undefined): string | null | undefined {
  if (!plaintext || typeof plaintext !== "string") return plaintext;

  const key = getStaticKey();
  if (!key) {
    console.warn(
      "[Encryption] STORAGE_ENCRYPTION_KEY not set. Storing plaintext (passthrough mode)."
    );
    return plaintext; // passthrough mode
  }

  // Already encrypted — don't double-encrypt
  if (plaintext.startsWith(PREFIX)) return plaintext;

  try {
    const iv = randomBytes(IV_LENGTH);
    const cipher = createCipheriv(ALGORITHM, key, iv);

    let encrypted = cipher.update(plaintext, "utf8", "hex");
    encrypted += cipher.final("hex");
    const authTag = cipher.getAuthTag().toString("hex");

    return `${PREFIX}${iv.toString("hex")}:${encrypted}:${authTag}`;
  } catch (err: unknown) {
    const message = err instanceof Error ? err.message : String(err);
    console.error(
      `[Encryption] Encryption failed: ${message}. ` +
        `Check your STORAGE_ENCRYPTION_KEY — generate one with: openssl rand -base64 32`
    );
    return plaintext; // fallback to plaintext rather than crashing
  }
}

/**
 * Decrypt a ciphertext string. Attempts static-salt key first (primary),
 * then falls back to legacy dynamic-salt key for backward compatibility.
 *
 * When a token is decrypted using the legacy key, it is flagged for
 * auto-migration: the next encrypt() call will re-encrypt it with the
 * static-salt key, gradually migrating the database.
 */
export function decrypt(
  ciphertext: string | null | undefined,
  opts?: { quiet?: boolean }
): string | null | undefined {
  if (!ciphertext || typeof ciphertext !== "string") return ciphertext;

  // Not encrypted — return as-is (legacy plaintext or passthrough mode)
  if (!ciphertext.startsWith(PREFIX)) return ciphertext;

  const staticKey = getStaticKey();
  if (!staticKey) {
    console.warn(
      "[Encryption] Found encrypted data but STORAGE_ENCRYPTION_KEY is not set. Cannot decrypt."
    );
    return null;
  }

  const body = ciphertext.slice(PREFIX.length);
  const parts = body.split(":");
  if (parts.length !== 3) {
    console.error("[Encryption] Malformed encrypted value");
    return null;
  }

  const [ivHex, encryptedHex, authTagHex] = parts;

  const tryDecryptWithKey = (candidateKey: Buffer): string | null => {
    try {
      const iv = Buffer.from(ivHex, "hex");
      const authTag = Buffer.from(authTagHex, "hex");
      const decipher = createDecipheriv(ALGORITHM, candidateKey, iv, {
        authTagLength: AUTH_TAG_LENGTH,
      });
      decipher.setAuthTag(authTag);

      let decrypted = decipher.update(encryptedHex, "hex", "utf8");
      decrypted += decipher.final("utf8");
      return decrypted;
    } catch {
      return null;
    }
  };

  try {
    // PRIMARY: Try static-salt key first (canonical derivation)
    const decrypted = tryDecryptWithKey(staticKey);
    if (decrypted !== null) {
      return decrypted;
    }

    // #9927 — the low-level generic log is suppressed when called through the
    // connection-decryption path (quiet:true); decryptConnectionFields emits a
    // single enriched message naming the credential + recovery path instead.
    if (!opts?.quiet) {
      console.error(
        `[Encryption] Decryption failed. Ciphertext prefix: ${ciphertext.slice(0, 30)}... ` +
          `Auth tag validation likely failed.`
      );
    }
    return null;
  } catch (err: unknown) {
    const message = err instanceof Error ? err.message : String(err);
    if (!opts?.quiet) {
      console.error("[Encryption] Decryption failed:", message);
    }
    return null;
  }
}

/**
 * Encrypt sensitive fields in a connection object (mutates in-place).
 * After decryption that required legacy key, re-encrypt with static key
 * to migrate tokens automatically.
 */
export function encryptConnectionFields<T extends ConnectionFields | null | undefined>(conn: T): T {
  if (!isEncryptionEnabled()) return conn;
  if (!conn) return conn;

  if (conn.apiKey) conn.apiKey = encrypt(conn.apiKey);
  if (conn.accessToken) conn.accessToken = encrypt(conn.accessToken);
  if (conn.refreshToken) conn.refreshToken = encrypt(conn.refreshToken);
  if (conn.idToken) conn.idToken = encrypt(conn.idToken);
  return conn;
}

/**
 * Decrypt sensitive fields in a connection row (returns new object).
 * Note: If any field was decrypted using the legacy key, the migration
 * flag is set. The calling code should check isMigrationNeeded() and
 * trigger a re-encrypt (write-back) to migrate those tokens to the static key.
 */
export function decryptConnectionFields<T extends ConnectionFields | null | undefined>(row: T): T {
  if (!row) return row;
  if (!isEncryptionEnabled()) return row;

  // quiet:true — the low-level generic decrypt() log is suppressed here so a
  // single failure emits ONE enriched message (below) naming the credential
  // and recovery path (#9927) instead of one generic line per field per cycle.
  const apiKey = decrypt(row.apiKey, { quiet: true });
  const accessToken = decrypt(row.accessToken, { quiet: true });
  const refreshToken = decrypt(row.refreshToken, { quiet: true });
  const idToken = decrypt(row.idToken, { quiet: true });

  // #6148 — a stored credential that is still encrypted (`enc:v1:…`) but
  // decrypts to null means the STORAGE_ENCRYPTION_KEY changed or was unset.
  // Flag it so callers surface a clear error instead of coercing the null to
  // "" and firing an empty-Bearer request that upstream rejects as 401.
  const credentialDecryptFailed =
    (looksEncrypted(row.apiKey) && apiKey === null) ||
    (looksEncrypted(row.accessToken) && accessToken === null) ||
    (looksEncrypted(row.refreshToken) && refreshToken === null) ||
    (looksEncrypted(row.idToken) && idToken === null);

  if (credentialDecryptFailed) {
    const failed: Array<{ field: string; value: unknown }> = [];
    if (looksEncrypted(row.apiKey) && apiKey === null) failed.push({ field: "apiKey", value: row.apiKey });
    if (looksEncrypted(row.accessToken) && accessToken === null)
      failed.push({ field: "accessToken", value: row.accessToken });
    if (looksEncrypted(row.refreshToken) && refreshToken === null)
      failed.push({ field: "refreshToken", value: row.refreshToken });
    if (looksEncrypted(row.idToken) && idToken === null) failed.push({ field: "idToken", value: row.idToken });

    const connectionId = typeof row.id === "string" ? row.id : "";
    const provider = typeof row.provider === "string" ? row.provider : "unknown";
    const fields = failed.map((f) => f.field).join(", ");

    // Dedupe per credential/row state: the sweep re-decrypts the same corrupt
    // row every cycle — log ONCE unless the failing state actually changes.
    const signature = decryptFailureSignature(connectionId, provider, failed);
    if (!loggedDecryptFailures.has(signature)) {
      loggedDecryptFailures.add(signature);
      console.error(
        `[Encryption] Failed to decrypt credential(s) [${fields}] for provider ` +
          `"${provider}" (connection ${connectionId || "unknown"}). ${RECOVERY_HINT}`
      );
    }
  }

  return {
    ...row,
    apiKey,
    accessToken,
    refreshToken,
    idToken,
    ...(credentialDecryptFailed ? { credentialDecryptFailed: true } : {}),
  };
}

/**
 * Specifically tests a ciphertext against the legacy key. If it succeeds, it
 * re-encrypts the decrypted value with the canonical static key.
 * Used exclusively by the startup migration script.
 */
export function migrateLegacyEncryptedString(ciphertext: string | null | undefined): {
  updated: boolean;
  value: string | null | undefined;
} {
  if (!isEncryptionEnabled()) return { updated: false, value: ciphertext };
  if (!ciphertext || ciphertext.trim().length === 0) return { updated: false, value: ciphertext };
  if (!ciphertext.startsWith(PREFIX)) return { updated: false, value: ciphertext };

  const staticKey = getStaticKey();
  const legacyKey = getLegacyDynamicKey();

  if (!staticKey) return { updated: false, value: null };

  const rawPayload = ciphertext.slice(PREFIX.length);
  const parts = rawPayload.split(":");
  if (parts.length !== 3) return { updated: false, value: ciphertext };

  const [ivHex, encryptedHex, authTagHex] = parts;
  const iv = Buffer.from(ivHex, "hex");
  const authTag = Buffer.from(authTagHex, "hex");
  const encrypted = Buffer.from(encryptedHex, "hex");

  const tryDecryptWithKey = (key: Buffer): string | null => {
    try {
      const decipher = createDecipheriv(ALGORITHM, key, iv, {
        authTagLength: AUTH_TAG_LENGTH,
      });
      decipher.setAuthTag(authTag);
      let decrypted = decipher.update(encrypted, undefined, "utf8");
      decrypted += decipher.final("utf8");
      return decrypted;
    } catch {
      return null;
    }
  };

  // 1. If it already decrypts with the static key, no migration needed.
  if (tryDecryptWithKey(staticKey) !== null) {
    return { updated: false, value: ciphertext };
  }

  // 2. If it decrypts with the legacy key, it needs migration!
  if (legacyKey) {
    const legacyDecrypted = tryDecryptWithKey(legacyKey);
    if (legacyDecrypted !== null) {
      // Re-encrypt using the canonical static key and return updated
      return { updated: true, value: encrypt(legacyDecrypted) };
    }
  }

  // 3. Un-decryptable or corrupted, leave it alone
  return { updated: false, value: ciphertext };
}