/**
 * This module provides a promise interface to the sqlite3 database module.
 */

const sqlite = require('sqlite3');
const pkg = require('./package.json'); // for sqlite3 version number

//-----------------------------------------------------------------------------
// The Database class
//-----------------------------------------------------------------------------

class Database {
  static get OPEN_READONLY() {
    return sqlite.OPEN_READONLY;
  }

  static get OPEN_READWRITE() {
    return sqlite.OPEN_READWRITE;
  }

  static get OPEN_CREATE() {
    return sqlite.OPEN_CREATE;
  }

  static get SQLITE3_VERSION() {
    return pkg.dependencies.sqlite3.substring(1);
  }

  static open(filename, mode) {
    let db = new Database();
    return db.open(filename, mode);
  }

  open(filename, mode) {
    if (typeof mode === 'undefined') {
      mode = Database.OPEN_READWRITE | Database.OPEN_CREATE;
    } else if (typeof mode !== 'number') {
      throw new TypeError('Database.open: mode is not a number');
    }
    return new Promise((resolve, reject) => {
      if (this.db) {
        return reject(new Error('Database.open: database is already open'));
      }
      let db = new sqlite.Database(filename, mode, (err) => {
        if (err) {
          reject(err);
        } else {
          this.db = db;
          this.filename = filename;
          resolve(this);
        }
      });
    });
  }

  on(evt, cb) {
    return this.db.on(evt, cb);
  }
  
  close(fn) {
    if (!this.db) {
      return Promise.reject(new Error('Database.close: database is not open'));
    }
    if (fn) {
      return fn(this)
        .then((result) => {
          return this.close().then((_) => {
            return result;
          });
        })
        .catch((err) => {
          return this.close().then((_) => {
            return Promise.reject(err);
          });
        });
    }
    return new Promise((resolve, reject) => {
      this.db.close((err) => {
        if (err) {
          reject(err);
        } else {
          this.db = null;
          resolve(this);
        }
      });
    });
  }

  run(...args) {
    return new Promise((resolve, reject) => {
      if (!this.db) {
        return reject(new Error('Database.run: database is not open'));
      }
      // Need a real function because 'this' is used.
      let callback = function (err) {
        if (err) {
          reject(err);
        } else {
          resolve({
            lastID: this.lastID,
            changes: this.changes,
          });
        }
      };
      args.push(callback);
      this.db.run.apply(this.db, args);
    });
  }

  get(...args) {
    return new Promise((resolve, reject) => {
      if (!this.db) {
        return reject(new Error('Database.get: database is not open'));
      }
      let callback = (err, row) => {
        if (err) {
          reject(err);
        } else {
          resolve(row);
        }
      };
      args.push(callback);
      this.db.get.apply(this.db, args);
    });
  }

  all(...args) {
    return new Promise((resolve, reject) => {
      if (!this.db) {
        return reject(new Error('Database.all: database is not open'));
      }
      let callback = (err, rows) => {
        if (err) {
          reject(err);
        } else {
          resolve(rows);
        }
      };
      args.push(callback);
      this.db.all.apply(this.db, args);
    });
  }

  each(...args) {
    if (args.length === 0 || typeof args[args.length - 1] !== 'function') {
      throw TypeError('Database.each: last arg is not a function');
    }
    return new Promise((resolve, reject) => {
      if (!this.db) {
        return reject(new Error('Database.each: database is not open'));
      }
      let callback = (err, nrows) => {
        if (err) {
          reject(err);
        } else {
          resolve(nrows);
        }
      };
      args.push(callback);
      this.db.each.apply(this.db, args);
    });
  }

  exec(sql) {
    return new Promise((resolve, reject) => {
      if (!this.db) {
        return reject(new Error('Database.exec: database is not open'));
      }
      this.db.exec(sql, (err) => {
        if (err) {
          reject(err);
        } else {
          resolve(this);
        }
      });
    });
  }

  transaction(fn) {
    return this.exec('BEGIN TRANSACTION').then((_) => {
      return fn(this)
        .then((result) => {
          return this.exec('END TRANSACTION').then((_) => {
            return result;
          });
        })
        .catch((err) => {
          return this.exec('ROLLBACK TRANSACTION').then((_) => {
            return Promise.reject(err);
          });
        });
    });
  }

  prepare(...args) {
    return new Promise((resolve, reject) => {
      if (!this.db) {
        return reject(new Error('Database.prepare: database is not open'));
      }
      let statement;
      let callback = (err) => {
        if (err) {
          reject(err);
        } else {
          resolve(new Statement(statement));
        }
      };
      args.push(callback);
      statement = this.db.prepare.apply(this.db, args);
    });
  }
}

//-----------------------------------------------------------------------------
// The Statement class
//-----------------------------------------------------------------------------

class Statement {
  constructor(statement) {
    if (!(statement instanceof sqlite.Statement)) {
      throw new TypeError(`Statement: 'statement' is not a statement instance`);
    }
    this.statement = statement;
  }

  bind(...args) {
    return new Promise((resolve, reject) => {
      let callback = (err) => {
        if (err) {
          reject(err);
        } else {
          resolve(this);
        }
      };
      args.push(callback);
      this.statement.bind.apply(this.statement, args);
    });
  }

  reset() {
    return new Promise((resolve, reject) => {
      this.statement.reset((_) => {
        resolve(this);
      });
    });
  }

  finalize() {
    return new Promise((resolve, reject) => {
      this.statement.finalize((err) => {
        if (err) {
          reject(err);
        } else {
          resolve(); // can't use it anymore
        }
      });
    });
  }

  run(...args) {
    return new Promise((resolve, reject) => {
      // Need a real function because 'this' is used.
      let callback = function (err) {
        if (err) {
          reject(err);
        } else {
          resolve({
            lastID: this.lastID,
            changes: this.changes,
          });
        }
      };
      args.push(callback);
      this.statement.run.apply(this.statement, args);
    });
  }

  get(...args) {
    return new Promise((resolve, reject) => {
      let callback = (err, row) => {
        if (err) {
          reject(err);
        } else {
          resolve(row);
        }
      };
      args.push(callback);
      this.statement.get.apply(this.statement, args);
    });
  }

  all(...args) {
    return new Promise((resolve, reject) => {
      let callback = (err, rows) => {
        if (err) {
          reject(err);
        } else {
          resolve(rows);
        }
      };
      args.push(callback);
      this.statement.all.apply(this.statement, args);
    });
  }

  each(...args) {
    if (args.length === 0 || typeof args[args.length - 1] !== 'function') {
      throw TypeError('Statement.each: last arg is not a function');
    }
    return new Promise((resolve, reject) => {
      let callback = (err, nrows) => {
        if (err) {
          reject(err);
        } else {
          resolve(nrows);
        }
      };
      args.push(callback);
      this.statement.each.apply(this.statement, args);
    });
  }
}

//-----------------------------------------------------------------------------
// Module Exports
//-----------------------------------------------------------------------------

module.exports = Database;