// Dependencies
var util = require('util');
var _ = require('@sailshq/lodash');
var debug = require('debug')('query');

module.exports = {


  friendlyName: 'Send native query',


  description: 'Send a native query to the MySQL database.',


  inputs: {

    connection: {
      friendlyName: 'Connection',
      description: 'An active database connection.',
      extendedDescription: 'The provided database connection instance must still be active.  Only database connection instances created by the `getConnection()` machine in this driver are supported.',
      example: '===',
      required: true
    },

    nativeQuery: {
      description: 'A native query for the database.',
      extendedDescription: 'If `valuesToEscape` is provided, this supports template syntax like `$1`, `$2`, etc.',
      whereToGet: {
        description: 'Write a native query for this database, or if this driver supports it, use `compileStatement()` to build a native query from Waterline syntax.',
        extendedDescription: 'This might be compiled from a Waterline statement (stage 4 query) using "Compile statement", however it could also originate directly from userland code.'
      },
      example: 'SELECT * FROM pets WHERE species=$1 AND nickname=$2',
      required: true
    },

    valuesToEscape: {
      description: 'An optional list of strings, numbers, or special literals (true, false, or null) to escape and include in the native query, in order.',
      extendedDescription: 'The first value in the list will be used to replace `$1`, the second value to replace `$2`, and so on.  Note that numbers, `true`, `false`, and `null` are interpreted _differently_ than if they were strings wrapped in quotes.  This array must never contain any arrays or dictionaries.',
      example: '===',
      defaultsTo: []
    },

    meta: {
      friendlyName: 'Meta (custom)',
      description: 'Additional stuff to pass to the driver.',
      extendedDescription: 'This is reserved for custom driver-specific extensions.  Please refer to the documentation for the driver you are using for more specific information.',
      example: '==='
    }

  },


  exits: {

    success: {
      description: 'The native query was executed successfully.',
      outputVariableName: 'report',
      outputDescription: 'The `result` property is the result data the database sent back.  The `meta` property is reserved for custom driver-specific extensions.',
      moreInfoUrl: 'https://github.com/felixge/node-mysql#getting-the-id-of-an-inserted-row',
      outputExample: '==='
      // outputExample: {
      //   result: '===',
      //   meta: '==='
      // }
    },

    queryFailed: {
      description: 'The database returned an error when attempting to execute the native query.',
      outputVariableName: 'report',
      outputDescription: 'The `error` property is a JavaScript Error instance with more details about what went wrong.  The `meta` property is reserved for custom driver-specific extensions.',
      outputExample: '==='
      // outputExample: {
      //   error: '===',
      //   meta: '==='
      // }
    },

    badConnection: {
      friendlyName: 'Bad connection',
      description: 'The provided connection is not valid or no longer active.  Are you sure it was obtained by calling this driver\'s `getConnection()` method?',
      extendedDescription: 'Usually, this means the connection to the database was lost due to a logic error or timing issue in userland code.  In production, this can mean that the database became overwhelemed or was shut off while some business logic was in progress.',
      outputVariableName: 'report',
      outputDescription: 'The `meta` property is reserved for custom driver-specific extensions.',
      outputExample: '==='
      // outputExample: {
      //   meta: '==='
      // }
    }

  },


  fn: function sendNativeQuery(inputs, exits) {
    var validateConnection = require('./private/validate-connection');

    // Validate provided connection.
    if (!validateConnection({ connection: inputs.connection }).execSync()) {
      return exits.badConnection({
        meta: inputs.meta
      });
    }


    // Validate provided native query.
    var sql = inputs.nativeQuery;
    var bindings = inputs.valuesToEscape || [];
    var queryInfo;


    debug('Running SQL Query:');
    debug('SQL: ' + sql);
    debug('Bindings: ' + bindings);
    debug('Connection Id: ' + inputs.connection.id);

    // If the meta flag is defined and it has a flag titled `isUsingQuestionMarks`
    // then the query was generated by Knex in compileStatement and the query
    // string is using `?` in place of values rather than the Waterline standardized
    // $1, $2, etc.
    if (!inputs.meta || !inputs.meta.isUsingQuestionMarks) {
      // Process SQL template, escaping bindings.
      // This converts `$1`, `$2`, etc. into the escaped binding.
      sql = sql.replace(/\$[1-9][0-9]*/g, function (substr){

        // e.g. `'$3'` => `'3'` => `3` => `2`
        var idx = +( substr.slice(1) ) - 1;

        // If no such binding exists, then just leave the original
        // template string (e.g. "$3") alone.
        if (idx >= bindings.length) {
          return substr;
        }

        // But otherwise, replace it with the escaped binding.
        return inputs.connection.escape(bindings[idx]);
      });

      // In this case the query has the values inline.
      queryInfo = sql;
    } else {
      queryInfo = {
        sql: sql,
        values: bindings
      };
    }

    debug('Compiled (final) SQL: ' + sql);

    // Send native query to the database using node-mysql.
    inputs.connection.query(queryInfo, function query() {
      // The exact format of the arguments for this callback are not part of
      // the officially documented behavior of node-mysql (at least not as
      // of March 2016 when this comment is being written).
      //
      // If you need to trace this down to the implementation, you might try
      // checking out the following links in order (from top to bottom):
      //  • https://github.com/felixge/node-mysql#performing-queries
      //  • https://github.com/felixge/node-mysql/blob/f5bd13d8c54ce524a6bff48bfceb15fdca3a938a/lib/protocol/ResultSet.js
      //  • https://github.com/felixge/node-mysql/blob/d4a5fd7b5e92a1e09bf3c85d24265eada8a84ad8/lib/protocol/sequences/Sequence.js#L96
      //  • https://github.com/felixge/node-mysql/blob/1720920f7afc660d37430c35c7128b20f77735e3/lib/protocol/sequences/Query.js#L94
      //  • https://github.com/felixge/node-mysql/blob/1720920f7afc660d37430c35c7128b20f77735e3/lib/protocol/sequences/Query.js#L144
      //
      // For example, here are the raw arguments provided to the `.query()`
      // callback for different types of queries:
      // ====================================================================
      // * * * * * *
      // CREATE TABLE
      // * * * * * *
      // ```
      // null,
      // {         // an OkPacket instance
      //   fieldCount: 0,
      //   affectedRows: 0,
      //   insertId: 0,
      //   serverStatus: 2,
      //   warningCount: 0,
      //   message: '',
      //   protocol41: true,
      //   changedRows: 0
      // },
      // undefined
      // ```
      //
      // * * * * * *
      // SELECT
      // * * * * * *
      // ```
      // null,
      // [        // an array of `RowDataPacket` instances:
      //   {
      //     id: 1,
      //     CustomerName: 'Cardinal',
      //     ...
      //   },
      //   ...
      // ],
      // [        // an array of `FieldPacket` instances:
      //   {
      //     catalog: 'def',
      //     db: 'mikermcneil',
      //     table: 'some_table',
      //     orgTable: 'some_table',
      //     name: 'id',
      //     orgName: 'id',
      //     charsetNr: 33,
      //     length: 765,
      //     type: 253,
      //     flags: 20483,
      //     decimals: 0,
      //     default: undefined,
      //     zeroFill: false,
      //     protocol41: true
      //   },
      //   ...
      // ]
      // ```
      //
      // * * * * * *
      // INSERT
      // * * * * * *
      // ```
      // null,
      // {             // an OkPacket instance
      //   fieldCount: 0,
      //   affectedRows: 1,
      //   insertId: 1,
      //   serverStatus: 2,
      //   warningCount: 0,
      //   message: '',
      //   protocol41: true,
      //   changedRows: 0
      // },
      // undefined
      // ```
      //
      // * * * * * *
      // DELETE
      // * * * * * *
      // ```
      // null,
      // {         // an OkPacket instance
      //   fieldCount: 0,
      //   affectedRows: 1,
      //   insertId: 0,
      //   serverStatus: 34,
      //   warningCount: 0,
      //   message: '',
      //   protocol41: true,
      //   changedRows: 0
      // },
      // undefined
      // ```
      // * * * * * *
      // UPDATE
      // * * * * * *
      // ```
      // null,
      // {         // an OkPacket instance
      //   fieldCount: 0,
      //   affectedRows: 1,
      //   insertId: 0,
      //   serverStatus: 34,
      //   warningCount: 0,
      //   message: '(Rows matched: 1  Changed: 1  Warnings: 0',
      //   protocol41: true,
      //   changedRows: 1
      // },
      // undefined
      // ```
      // ====================================================================


      // If the first argument is truthy, then treat it as an error.
      // (i.e. close shop early &gtfo; via the `queryFailed` exit)
      if (arguments[0]) {
        return exits.queryFailed({
          error: arguments[0],
          meta: inputs.meta
        });
      }


      // Otherwise, the query was successful.

      // Since the arguments passed to this callback and their data format
      // can vary across different types of queries, we do our best to normalize
      // that here.  However, in order to do so, we have to be somewhat
      // opinionated; i.e. using the following heuristics when building the
      // standard `result` dictionary:
      //  • If the 2nd arg is an array, we expose it as `result.rows`.
      //  • Otherwise if the 2nd arg is a dictionary, we expose it as `result`.
      //  • If the 3rd arg is an array, we include it as `result.fields`.
      //    (if the 3rd arg is an array AND the 2nd arg is a dictionary, then
      //     the 3rd arg is tacked on as the `fields` property of the 2nd arg.
      //     If the 2nd arg already had `fields`, it is overridden.)
      var normalizedNativeResult;
      if (arguments[1]) {
        // `result :=`
        // `result.rows :=`
        if (_.isArray(arguments[1])) {
          normalizedNativeResult = { rows: arguments[1] };

          // `result :=`
        } else if (_.isObject(arguments[1])) {
          normalizedNativeResult = arguments[1];
        } else {
          return exits.error(new Error('Query was successful, but output from node-mysql is in an unrecognized format.  Output:\n' + util.inspect(Array.prototype.slice.call(arguments), { depth: null })));
        }
      }

      if (arguments[2]) {
        // `result.fields :=`
        if (_.isArray(arguments[2])) {
          normalizedNativeResult.fields = arguments[2];
        } else {
          return exits.error(new Error('Query was successful, but output from node-mysql is in an unrecognized format.  Output:\n' + util.inspect(Array.prototype.slice.call(arguments), { depth: null })));
        }
      }

      // Finally, return the normalized result.
      return exits.success({
        result: normalizedNativeResult,
        meta: inputs.meta
      });
    });
  }


};