export const POSTGRES_IDENTIFIER_MAX_LENGTH = 63;
export const PLAY_NAME_MAX_LENGTH = POSTGRES_IDENTIFIER_MAX_LENGTH;
export const MAP_KEY_NAMESPACE_MAX_LENGTH = POSTGRES_IDENTIFIER_MAX_LENGTH;
export const DEFAULT_TABLE_NAMESPACE = 'sheet';
export const DEFAULT_INTERNAL_TABLE_NAMESPACE = '_key';

const SHA256_INITIAL_HASH: number[] = [
  0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c,
  0x1f83d9ab, 0x5be0cd19,
];

const SHA256_ROUND_CONSTANTS: number[] = [
  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
  0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
  0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
  0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
  0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
  0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
  0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
  0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
  0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
  0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
  0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
];

function stableValue(value: unknown): unknown {
  if (Array.isArray(value)) {
    return value.map((entry) => stableValue(entry));
  }
  if (value && typeof value === 'object') {
    return Object.fromEntries(
      Object.entries(value as Record<string, unknown>)
        .filter(([, entry]) => entry !== undefined)
        .sort(([left], [right]) => left.localeCompare(right))
        .map(([key, entry]) => [key, stableValue(entry)]),
    );
  }
  return value;
}

export function stableStringify(value: unknown): string {
  return JSON.stringify(stableValue(value));
}

function rightRotate32(value: number, bits: number): number {
  return (value >>> bits) | (value << (32 - bits));
}

export function sha256Hex(input: string): string {
  const bytes = Array.from(new TextEncoder().encode(input));
  const bitLength = bytes.length * 8;
  bytes.push(0x80);
  while (bytes.length % 64 !== 56) {
    bytes.push(0);
  }

  const highBits = Math.floor(bitLength / 0x100000000);
  const lowBits = bitLength >>> 0;
  bytes.push(
    (highBits >>> 24) & 0xff,
    (highBits >>> 16) & 0xff,
    (highBits >>> 8) & 0xff,
    highBits & 0xff,
    (lowBits >>> 24) & 0xff,
    (lowBits >>> 16) & 0xff,
    (lowBits >>> 8) & 0xff,
    lowBits & 0xff,
  );

  const hash = [...SHA256_INITIAL_HASH];
  const words = new Array<number>(64).fill(0);

  for (let offset = 0; offset < bytes.length; offset += 64) {
    for (let index = 0; index < 16; index += 1) {
      const wordOffset = offset + index * 4;
      words[index] =
        ((bytes[wordOffset] ?? 0) << 24) |
        ((bytes[wordOffset + 1] ?? 0) << 16) |
        ((bytes[wordOffset + 2] ?? 0) << 8) |
        (bytes[wordOffset + 3] ?? 0);
    }

    for (let index = 16; index < 64; index += 1) {
      const s0 =
        rightRotate32(words[index - 15], 7) ^
        rightRotate32(words[index - 15], 18) ^
        (words[index - 15] >>> 3);
      const s1 =
        rightRotate32(words[index - 2], 17) ^
        rightRotate32(words[index - 2], 19) ^
        (words[index - 2] >>> 10);
      words[index] = (words[index - 16] + s0 + words[index - 7] + s1) >>> 0;
    }

    let [a, b, c, d, e, f, g, h] = hash;
    for (let index = 0; index < 64; index += 1) {
      const s1 =
        rightRotate32(e, 6) ^ rightRotate32(e, 11) ^ rightRotate32(e, 25);
      const ch = (e & f) ^ (~e & g);
      const temp1 =
        (h + s1 + ch + SHA256_ROUND_CONSTANTS[index] + words[index]) >>> 0;
      const s0 =
        rightRotate32(a, 2) ^ rightRotate32(a, 13) ^ rightRotate32(a, 22);
      const maj = (a & b) ^ (a & c) ^ (b & c);
      const temp2 = (s0 + maj) >>> 0;

      h = g;
      g = f;
      f = e;
      e = (d + temp1) >>> 0;
      d = c;
      c = b;
      b = a;
      a = (temp1 + temp2) >>> 0;
    }

    hash[0] = (hash[0] + a) >>> 0;
    hash[1] = (hash[1] + b) >>> 0;
    hash[2] = (hash[2] + c) >>> 0;
    hash[3] = (hash[3] + d) >>> 0;
    hash[4] = (hash[4] + e) >>> 0;
    hash[5] = (hash[5] + f) >>> 0;
    hash[6] = (hash[6] + g) >>> 0;
    hash[7] = (hash[7] + h) >>> 0;
  }

  return hash.map((word) => word.toString(16).padStart(8, '0')).join('');
}

function sanitizeIdentifierPart(value: string): string {
  return value
    .trim()
    .replace(/[^a-z0-9]+/gi, '_')
    .replace(/_+/g, '_')
    .replace(/^_+|_+$/g, '')
    .toLowerCase();
}

function validateIdentifierPart(
  rawValue: string,
  label: string,
  maxLength: number,
): string {
  const sanitized = sanitizeIdentifierPart(rawValue);
  if (!sanitized) {
    throw new Error(`${label} must contain a letter or number.`);
  }

  if (sanitized.length > maxLength) {
    throw new Error(
      `${label} is too long after normalization (${sanitized.length}/${maxLength}): "${sanitized}".`,
    );
  }

  return sanitized;
}

export function normalizePlayName(value: string): string {
  if (value.includes('/')) {
    throw new Error(
      'Play name cannot contain "/". Slash is reserved.',
    );
  }
  return validateIdentifierPart(value, 'Play name', PLAY_NAME_MAX_LENGTH);
}

/**
 * Normalize a play name into the leading segment of a physical sheet table name.
 *
 * A qualified reference like "prebuilt/name-and-domain-to-email-waterfall" folds
 * its namespace separator into a plain identifier
 * ("prebuilt_name_and_domain_to_email_waterfall") so the physical table reads
 * cleanly. `validatePlaySheetTableName` enforces the 63-char Postgres identifier
 * limit on the play + namespace combination and fails loudly when a name is
 * genuinely too long — no opaque content digest is mixed into the table name.
 */
export function normalizePlayNameForSheet(value: string): string {
  if (!value.includes('/')) {
    return normalizePlayName(value);
  }
  return validateIdentifierPart(
    value.replace(/\//g, '_'),
    'Play name',
    PLAY_NAME_MAX_LENGTH,
  );
}

export function normalizeTableNamespace(value: string): string {
  return validateIdentifierPart(
    value,
    'ctx.dataset() key',
    MAP_KEY_NAMESPACE_MAX_LENGTH,
  );
}

export function validatePlaySheetTableName(
  playName: string,
  tableNamespace: string,
): string {
  const playSegment = normalizePlayNameForSheet(playName);
  const keySegment = normalizeTableNamespace(tableNamespace);
  const resolved = `${playSegment}_${keySegment}`;
  if (resolved.length > POSTGRES_IDENTIFIER_MAX_LENGTH) {
    throw new Error(
      `Play sheet table name is too long after normalization (${resolved.length}/63): "${resolved}".`,
    );
  }
  return resolved;
}

export function derivePlayRowIdentity(
  row: Record<string, unknown>,
  tableNamespace: string,
): string {
  return deriveDerivedOutputIdentity({
    inputItem: row,
    operationNamespace: tableNamespace,
  });
}

export function deriveDerivedOutputIdentity(input: {
  inputItem: Record<string, unknown>;
  operationNamespace: string;
}): string {
  const normalizedNamespace = normalizeTableNamespace(input.operationNamespace);
  const canonicalRow = stableStringify(input.inputItem);
  const digest = sha256Hex(`${normalizedNamespace}\n${canonicalRow}`);
  return `${normalizedNamespace}:${digest}`;
}

export function deriveToolRequestIdentity(input: {
  toolId: string;
  requestInput: Record<string, unknown>;
}): string {
  const toolId = input.toolId.trim();
  if (!toolId) {
    throw new Error('Tool request identity requires a non-empty tool id.');
  }
  const digest = sha256Hex(
    stableStringify({
      requestInput: input.requestInput,
      toolId,
    }),
  );
  return `tool:${normalizeTableNamespace(toolId)}:${digest}`;
}

/**
 * Build a stable row identity from an explicit user-provided key string.
 *
 * Use when the caller wants to pin row identity to a primary column
 * (e.g. row.email) instead of hashing the full row contents — so harmless
 * mutations to other columns don't invalidate the cache.
 */
export function derivePlayRowIdentityFromKey(
  key: string,
  tableNamespace: string,
): string {
  const normalizedNamespace = normalizeTableNamespace(tableNamespace);
  const digest = sha256Hex(`${normalizedNamespace}\nkey:${key}`);
  return `${normalizedNamespace}:${digest}`;
}