import fs from "fs";

const MYSQL_INDEX_PREFIX_LENGTH = 191;
const MYSQL_TABLE_OPTIONS = "ENGINE = InnoDB ROW_FORMAT = DYNAMIC";
/**
 * ## sqlite与postgres不同点
 * 1.
 * sqlite: AUTOINCREAMENT
 * postgresql: GENERATED BY DEFAULT AS IDENTITY
 *
 * 2.
 * sqlite: datetime
 * postgresql: timestamp
 *
 * 3.
 * sqlite: update sqlite_sequence set seq = 1000 where name = 'sys_role' ;
 * postgresql: select setval('sys_role_id_seq', 1000);
 *
 * 4.
 * sqlite: "disabled" boolean DEFAULT (0)
 * postgresql: "disabled" boolean DEFAULT (false)
 *
 * 5.
 * sqlite: last_insert_rowid()
 * postgresql: LASTVAL()
 *
 * 6.
 * sqlite: integer
 * postgresql: bigint
 */
function transformPG() {
  // 读取文件列表
  const sqliteFiles = fs.readdirSync("./migration/");
  const pgFiles = fs.readdirSync("./migration-pg/");
  //找出pg里面没有的文件
  const notFiles = sqliteFiles.filter(file => !pgFiles.includes(file));
  for (const notFile of notFiles) {
    //开始转换
    const sqliteSql = fs.readFileSync(`./migration/${notFile}`, "utf-8");
    let pgSql = sqliteSql.replaceAll(/AUTOINCREMENT/g, "GENERATED BY DEFAULT AS IDENTITY");
    pgSql = pgSql.replaceAll(/datetime/g, "timestamp");
    pgSql = pgSql.replaceAll(/boolean DEFAULT \(0\)/g, "boolean DEFAULT (false)");
    pgSql = pgSql.replaceAll(/boolean DEFAULT \(1\)/g, "boolean DEFAULT (true)");
    pgSql = pgSql.replaceAll(/boolean.*NOT NULL DEFAULT \(0\)/g, "boolean NOT NULL DEFAULT (false)");
    pgSql = pgSql.replaceAll(/boolean.*NOT NULL DEFAULT \(1\)/g, "boolean NOT NULL DEFAULT (true)");
    pgSql = pgSql.replaceAll(/integer/g, "bigint");
    pgSql = pgSql.replaceAll(/INTEGER/g, "bigint");
    pgSql = pgSql.replaceAll(/last_insert_rowid\(\)/g, "LASTVAL()");
    fs.writeFileSync(`./migration-pg/${notFile}`, pgSql);
  }

  if (notFiles.length > 0) {
    console.log("sqlite->pg 转换完成");

    throw new Error("sqlite->pg 转换完成，有更新，需要测试pg");
  } else {
    console.log("sql无需更新");
  }
}

function buildMysqlTableColumnMap(sql) {
  const tableColumnMap = new Map();
  const createTableReg = /CREATE TABLE `([^`]*)`[\s\S]*?;/gi;
  for (const match of sql.matchAll(createTableReg)) {
    const [statement, tableName] = match;
    const tableBody = getCreateTableBody(statement);
    const columnMap = new Map();
    const columnReg = /`([^`]*)`\s+varchar\((\d+)\)/gi;
    for (const columnMatch of tableBody.matchAll(columnReg)) {
      const [, columnName, length] = columnMatch;
      columnMap.set(columnName, Number(length));
    }
    tableColumnMap.set(tableName, columnMap);
  }

  const alterAddColumnReg = /ALTER TABLE\s+`?([^`\s]+)`?\s+ADD COLUMN\s+`?([^`\s]+)`?\s+varchar\((\d+)\)/gi;
  for (const match of sql.matchAll(alterAddColumnReg)) {
    const [, tableName, columnName, length] = match;
    const columnMap = tableColumnMap.get(tableName) || new Map();
    columnMap.set(columnName, Number(length));
    tableColumnMap.set(tableName, columnMap);
  }

  return tableColumnMap;
}

function getCreateTableBody(statement) {
  const start = statement.indexOf("(");
  const end = statement.lastIndexOf(")");
  if (start === -1 || end === -1 || end <= start) {
    return "";
  }
  return statement.substring(start + 1, end);
}

function appendMysqlTableOptions(sql) {
  const createTableReg = /CREATE TABLE `([^`]*)`[\s\S]*?;/gi;
  return sql.replace(createTableReg, statement => {
    const sqlWithoutSemicolon = statement.replace(/;\s*$/, "");
    const sqlWithoutOptions = sqlWithoutSemicolon.replace(/\s+ENGINE\s*=\s*\w+(?:\s+ROW_FORMAT\s*=\s*\w+)?\s*$/i, "");
    return `${sqlWithoutOptions} ${MYSQL_TABLE_OPTIONS};`;
  });
}

function addMysqlIndexPrefix(sql) {
  const tableColumnMap = buildMysqlTableColumnMap(sql);
  const createIndexReg = /CREATE\s+(UNIQUE\s+)?INDEX\s+`([^`]*)`\s+ON\s+`([^`]*)`\s*\(([^;]*)\);/gi;
  return sql.replace(createIndexReg, (statement, uniqueKeyword, indexName, tableName, columns) => {
    const columnMap = tableColumnMap.get(tableName);
    if (!columnMap) {
      return statement;
    }

    const parsedColumns = columns.split(",").map(item => {
      const columnMatch = item.trim().match(/^`([^`]*)`(?:\((\d+)\))?$/);
      if (!columnMatch) {
        return item.trim();
      }

      const [, columnName, prefixLength] = columnMatch;
      const columnLength = columnMap.get(columnName);
      if (!columnLength || columnLength <= MYSQL_INDEX_PREFIX_LENGTH) {
        return item.trim();
      }

      if (prefixLength && Number(prefixLength) <= MYSQL_INDEX_PREFIX_LENGTH) {
        return item.trim();
      }

      // MySQL 5.7 老配置下 utf8mb4 varchar(255) 完整索引可能超过 767/1000 字节限制。
      if (uniqueKeyword) {
        throw new Error(`唯一索引 ${indexName} 的字段 ${tableName}.${columnName} 长度超过 ${MYSQL_INDEX_PREFIX_LENGTH}，不能自动改成前缀索引，请缩短字段长度或增加 hash 字段`);
      }

      return `\`${columnName}\`(${MYSQL_INDEX_PREFIX_LENGTH})`;
    });

    const unique = uniqueKeyword || "";
    return `CREATE ${unique}INDEX \`${indexName}\` ON \`${tableName}\` (${parsedColumns.join(", ")});`;
  });
}

function transformMysql() {
  // 读取文件列表
  const sqliteFiles = fs.readdirSync("./migration/");
  const pgFiles = fs.readdirSync("./migration-mysql/");
  //找出pg里面没有的文件
  const notFiles = sqliteFiles.filter(file => !pgFiles.includes(file));
  for (const notFile of notFiles) {
    //开始转换
    const sqliteSql = fs.readFileSync(`./migration/${notFile}`, "utf-8");
    let pgSql = sqliteSql.replaceAll(/AUTOINCREMENT/g, "AUTO_INCREMENT");
    pgSql = pgSql.replaceAll(/datetime/g, "timestamp");
    //DEFAULT (xxx) 替换成 DEFAULT xxx
    pgSql = pgSql.replaceAll(/DEFAULT \(([^)]*)\)/g, "DEFAULT $1");
    pgSql = pgSql.replaceAll(/integer/g, "bigint");
    pgSql = pgSql.replaceAll(/INTEGER/g, "bigint");
    pgSql = pgSql.replaceAll(/last_insert_rowid\(\)/g, "LAST_INSERT_ID()");
    //text 改成longtext
    pgSql = pgSql.replaceAll(/text/g, "longtext");
    //双引号 替换成反引号
    pgSql = pgSql.replaceAll(/"/g, "`");

    pgSql = appendMysqlTableOptions(pgSql);
    pgSql = addMysqlIndexPrefix(pgSql);

    fs.writeFileSync(`./migration-mysql/${notFile}`, pgSql);
  }

  if (notFiles.length > 0) {
    console.log("sqlite->mysql 转换完成");

    throw new Error("sqlite->mysql 转换完成，有更新，需要测试mysql");
  } else {
    console.log("sql无需更新");
  }
}

transformPG();
transformMysql();