import type { Db, ExecResult, Row } from "./driver.ts";
import type { Model } from "./schema.ts";
import type { Dialect } from "./sql.ts";

const IDENTIFIER = /^[A-Za-z_][A-Za-z0-9_]*$/;

function identifier(value: string): string {
  if (!IDENTIFIER.test(value)) throw new TypeError(`Unsafe SQL identifier: ${value}`);
  return value;
}

function placeholder(dialect: Dialect, index: number): string {
  return dialect === "postgres" ? `$${index}` : "?";
}

function placeholders(dialect: Dialect, count: number, start = 1): string[] {
  return Array.from({ length: count }, (_value, index) => placeholder(dialect, start + index));
}

function finiteInteger(value: number | undefined, fallback: number, minimum: number): number {
  if (value === undefined) return fallback;
  if (!Number.isFinite(value)) throw new RangeError("Expected a finite integer.");
  return Math.max(minimum, Math.floor(value));
}

export class RecordNotFoundError extends Error {
  constructor(message = "Record not found") {
    super(message);
    this.name = "RecordNotFoundError";
  }
}

export async function firstOrThrow<T>(
  db: Db,
  sql: string,
  params: unknown[] = [],
  model?: Model<T>,
  message?: string,
): Promise<T> {
  const row = await db.one(sql, params, model);
  if (row === null) throw new RecordNotFoundError(message);
  return row;
}

export async function exists(db: Db, sql: string, params: unknown[] = []): Promise<boolean> {
  return (await db.one(sql, params)) !== null;
}

export async function countRows(
  db: Db,
  table: string,
  where = "",
  params: unknown[] = [],
): Promise<number> {
  const row = await db.one<{ count: number | string }>(
    `SELECT COUNT(*) AS count FROM ${identifier(table)}${where ? ` WHERE ${where}` : ""}`,
    params,
  );
  return Number(row?.count ?? 0);
}

export function withTransaction<T>(db: Db, callback: (tx: Db) => Promise<T>): Promise<T> {
  return db.tx(callback);
}

/** Execute a parameterized compare-and-set update and report whether this caller won. */
export async function compareAndSet(
  db: Db,
  options: {
    table: string;
    idColumn?: string;
    id: string | number;
    stateColumn?: string;
    from: string;
    to: string;
    extra?: Record<string, unknown>;
  },
): Promise<boolean> {
  const table = identifier(options.table);
  const idColumn = identifier(options.idColumn ?? "id");
  const stateColumn = identifier(options.stateColumn ?? "status");
  const entries = Object.entries(options.extra ?? {});
  const assignments = [stateColumn, ...entries.map(([name]) => identifier(name))];
  const dialect = db.driver.dialect;
  const values = [options.to, ...entries.map(([, value]) => value), options.id, options.from];
  const sql = `UPDATE ${table} SET ${assignments
    .map((name, index) => `${name} = ${placeholder(dialect, index + 1)}`)
    .join(
      ", ",
    )} WHERE ${idColumn} = ${placeholder(dialect, assignments.length + 1)} AND ${stateColumn} = ${placeholder(dialect, assignments.length + 2)}`;
  return (await db.exec(sql, values)).changes === 1;
}

/** Conservative default classifier for deadlock/serialization retry errors. */
export function isRetryableTransactionError(error: unknown): boolean {
  if (!error || typeof error !== "object") return false;
  const value = error as { code?: unknown; errno?: unknown; message?: unknown };
  const code = String(value.code ?? value.errno ?? "").toUpperCase();
  if (["40001", "40P01", "SQLITE_BUSY", "SQLITE_LOCKED", "1213", "1205"].includes(code)) {
    return true;
  }
  const message = String(value.message ?? "").toLowerCase();
  return /deadlock|serialization failure|database is locked|lock wait timeout/.test(message);
}

export async function retryTransaction<T>(
  db: Db,
  callback: (tx: Db, attempt: number) => Promise<T>,
  options: {
    attempts?: number;
    baseDelayMs?: number;
    maxDelayMs?: number;
    jitter?: boolean;
    shouldRetry?: (error: unknown) => boolean;
  } = {},
): Promise<T> {
  const attempts = finiteInteger(options.attempts, 3, 1);
  const baseDelayMs = finiteInteger(options.baseDelayMs, 25, 0);
  const maxDelayMs = finiteInteger(options.maxDelayMs, 1_000, 0);
  const shouldRetry = options.shouldRetry ?? isRetryableTransactionError;
  let lastError: unknown;
  for (let attempt = 1; attempt <= attempts; attempt++) {
    try {
      return await db.tx((tx) => callback(tx, attempt));
    } catch (error) {
      lastError = error;
      if (attempt >= attempts || !shouldRetry(error)) throw error;
      const exponential = Math.min(maxDelayMs, baseDelayMs * 2 ** (attempt - 1));
      const delay =
        options.jitter === false
          ? exponential
          : Math.round(exponential * (0.5 + Math.random() * 0.5));
      await new Promise((resolve) => setTimeout(resolve, delay));
    }
  }
  throw lastError;
}

export function batch<T>(values: readonly T[], size = 100): T[][] {
  const chunkSize = finiteInteger(size, 100, 1);
  const chunks: T[][] = [];
  for (let index = 0; index < values.length; index += chunkSize) {
    chunks.push(values.slice(index, index + chunkSize));
  }
  return chunks;
}

export async function databaseHealth(
  db: Db,
): Promise<{ ok: boolean; latencyMs: number; error?: string }> {
  const start = performance.now();
  try {
    await db.one("SELECT 1 AS healthy");
    return { ok: true, latencyMs: Math.round((performance.now() - start) * 100) / 100 };
  } catch (error) {
    return {
      ok: false,
      latencyMs: Math.round((performance.now() - start) * 100) / 100,
      error: error instanceof Error ? error.message : String(error),
    };
  }
}

export interface RepositoryListOptions<T extends Row> {
  limit?: number;
  offset?: number;
  orderBy?: keyof T & string;
  direction?: "asc" | "desc";
}

export interface Repository<T extends Row> {
  all(options?: RepositoryListOptions<T>): Promise<T[]>;
  find(id: string | number): Promise<T | null>;
  require(id: string | number): Promise<T>;
  create(values: Partial<T>): Promise<ExecResult>;
  update(id: string | number, values: Partial<T>): Promise<ExecResult>;
  remove(id: string | number): Promise<ExecResult>;
  exists(id: string | number): Promise<boolean>;
  count(): Promise<number>;
}

export function createRepository<T extends Row>(
  db: Db,
  input: {
    table: string;
    idColumn?: string;
    model?: Model<T>;
    allowedColumns?: readonly (keyof T & string)[];
    maxListLimit?: number;
    /** Immutable equality scope (normally tenant_id) applied to every operation. */
    scope?: { column: keyof T & string; value: unknown };
  },
): Repository<T> {
  const table = identifier(input.table);
  const idColumn = identifier(input.idColumn ?? "id");
  const allowed = input.allowedColumns ? new Set(input.allowedColumns.map(identifier)) : null;
  const dialect = db.driver.dialect;
  const maxListLimit = finiteInteger(input.maxListLimit, 1_000, 1);
  const scopeColumn = input.scope ? identifier(input.scope.column) : null;
  const valuesOf = (values: Partial<T>) => {
    const entries = Object.entries(values).filter(([key, value]) => {
      if (value === undefined || key === idColumn) return false;
      identifier(key);
      return !allowed || allowed.has(key) || key === scopeColumn;
    });
    if (!entries.length)
      throw new TypeError("Repository write requires at least one allowed column.");
    return entries;
  };
  const allowedReadColumn = (value: string): string => {
    const safe = identifier(value);
    if (allowed && safe !== idColumn && !allowed.has(safe)) {
      throw new TypeError(`Repository column is not allowed: ${safe}`);
    }
    return safe;
  };

  return {
    all: (options = {}) => {
      const clauses: string[] = scopeColumn
        ? [`WHERE ${scopeColumn} = ${placeholder(dialect, 1)}`]
        : [];
      const params: unknown[] = scopeColumn ? [input.scope!.value] : [];
      if (options.orderBy) {
        clauses.push(
          `ORDER BY ${allowedReadColumn(options.orderBy)} ${(options.direction ?? "asc").toUpperCase()}`,
        );
      }
      if (options.limit !== undefined) {
        const limit = Math.min(maxListLimit, finiteInteger(options.limit, maxListLimit, 1));
        params.push(limit);
        clauses.push(`LIMIT ${placeholder(dialect, params.length)}`);
      }
      if (options.offset !== undefined) {
        const offset = finiteInteger(options.offset, 0, 0);
        if (options.limit === undefined) {
          params.push(maxListLimit);
          clauses.push(`LIMIT ${placeholder(dialect, params.length)}`);
        }
        params.push(offset);
        clauses.push(`OFFSET ${placeholder(dialect, params.length)}`);
      }
      return db.all<T>(
        `SELECT * FROM ${table}${clauses.length ? ` ${clauses.join(" ")}` : ""}`,
        params,
        input.model,
      );
    },
    find: (id) =>
      db.one<T>(
        `SELECT * FROM ${table} WHERE ${idColumn} = ${placeholder(dialect, 1)}${scopeColumn ? ` AND ${scopeColumn} = ${placeholder(dialect, 2)}` : ""} LIMIT 1`,
        scopeColumn ? [id, input.scope!.value] : [id],
        input.model,
      ),
    require: (id) =>
      firstOrThrow<T>(
        db,
        `SELECT * FROM ${table} WHERE ${idColumn} = ${placeholder(dialect, 1)}${scopeColumn ? ` AND ${scopeColumn} = ${placeholder(dialect, 2)}` : ""} LIMIT 1`,
        scopeColumn ? [id, input.scope!.value] : [id],
        input.model,
      ),
    async create(values) {
      const scoped = scopeColumn ? { ...values, [scopeColumn]: input.scope!.value } : values;
      const entries = valuesOf(scoped);
      return db.exec(
        `INSERT INTO ${table} (${entries.map(([key]) => identifier(key)).join(", ")}) VALUES (${placeholders(dialect, entries.length).join(", ")})`,
        entries.map(([, value]) => value),
      );
    },
    async update(id, values) {
      const entries = valuesOf(values);
      return db.exec(
        `UPDATE ${table} SET ${entries
          .map(([key], index) => `${identifier(key)} = ${placeholder(dialect, index + 1)}`)
          .join(
            ", ",
          )} WHERE ${idColumn} = ${placeholder(dialect, entries.length + 1)}${scopeColumn ? ` AND ${scopeColumn} = ${placeholder(dialect, entries.length + 2)}` : ""}`,
        [...entries.map(([, value]) => value), id, ...(scopeColumn ? [input.scope!.value] : [])],
      );
    },
    remove: (id) =>
      db.exec(
        `DELETE FROM ${table} WHERE ${idColumn} = ${placeholder(dialect, 1)}${scopeColumn ? ` AND ${scopeColumn} = ${placeholder(dialect, 2)}` : ""}`,
        scopeColumn ? [id, input.scope!.value] : [id],
      ),
    exists: (id) =>
      exists(
        db,
        `SELECT 1 FROM ${table} WHERE ${idColumn} = ${placeholder(dialect, 1)}${scopeColumn ? ` AND ${scopeColumn} = ${placeholder(dialect, 2)}` : ""} LIMIT 1`,
        scopeColumn ? [id, input.scope!.value] : [id],
      ),
    count: () =>
      scopeColumn
        ? db
            .one<{ count: number | string }>(
              `SELECT COUNT(*) AS count FROM ${table} WHERE ${scopeColumn} = ${placeholder(dialect, 1)}`,
              [input.scope!.value],
            )
            .then((row) => Number(row?.count ?? 0))
        : countRows(db, table),
  };
}