// SchemaGrammar
// -------

// The "SchemaGrammar" is a layer which helps in compiling
// valid data definition language (DDL) statements in
// to create, alter, or destroy the various tables, columns,
// and metadata in our database schema. These functions
// are combined with dialect specific "SchemaGrammar"
// functions to keep the interface database agnostic.
var _             = require('lodash');

var baseGrammar   = require('./grammar').baseGrammar;
var SchemaBuilder = require('../../lib/schemabuilder').SchemaBuilder;

var Helpers       = require('../../lib/helpers').Helpers;
var Raw           = require('../../lib/raw').Raw;

exports.baseSchemaGrammar = {

  // The toSql on the "schema" is different than that on the "builder",
  // it produces an array of sql statements to be used in the creation
  // or modification of the query, which are each run in sequence
  // on the same connection.
  toSql: function(builder) {

    // Clone the builder, before we go about working with the columns & commands.
    // TODO: Clean this up.
    builder = builder.clone();

    // Add the commands that are implied by the blueprint.
    if (builder.columns.length > 0 && !builder.creating()) {
      builder.commands.unshift({name: 'add'});
    }

    // Add an "additional" command, for any extra dialect-specific logic.
    builder.commands.push({name: 'additional'});

    // Add indicies
    for (var i = 0, l = builder.columns.length; i < l; i++) {
      var column = builder.columns[i];
      var indices = ['primary', 'unique', 'index', 'foreign'];

      continueIndex:
      for (var i2 = 0, l2 = indices.length; i2 < l2; i2++) {
        var index = indices[i2];
        var indexVar = 'is' + Helpers.capitalize(index);

        // If the index has been specified on the given column, but is simply
        // equal to "true" (boolean), no name has been specified for this
        // index, so we will simply call the index methods without one.
        if (column[indexVar] === true) {
          builder[index](column, null);
          continue continueIndex;

        // If the index has been specified on the column and it is something
        // other than boolean true, we will assume a name was provided on
        // the index specification, and pass in the name to the method.
        } else if (_.has(column, indexVar)) {
          builder[index](column.name, column[indexVar], column);
          continue continueIndex;
        }
      }
    }

    var statements = [];

    // Each type of command has a corresponding compiler function on the schema
    // grammar which is used to build the necessary SQL statements to build
    // the blueprint element, so we'll just call that compilers function.
    for (i = 0, l = builder.commands.length; i < l; i++) {
      var command = builder.commands[i];
      var method = 'compile' + Helpers.capitalize(command.name);
      if (_.has(this, method)) {
        var sql = this[method](builder, command);
        if (sql) statements = statements.concat(sql);
      }
    }

    return statements;
  },

  // Compile a foreign key command.
  compileForeign: function(blueprint, command) {
    var sql;
    if (command.foreignTable && command.foreignColumn) {
      var table = this.wrapTable(blueprint);
      var column = this.columnize(command.columns);
      var foreignTable = this.wrapTable(command.foreignTable);
      var foreignColumn = this.columnize(command.foreignColumn);

      sql = "alter table " + table + " add constraint " + command.index + " ";
      sql += "foreign key (" + column + ") references " + foreignTable + " (" + foreignColumn + ")";

      // Once we have the basic foreign key creation statement constructed we can
      // build out the syntax for what should happen on an update or delete of
      // the affected columns, which will get something like "cascade", etc.
      if (command.commandOnDelete) sql += " on delete " + command.commandOnDelete;
      if (command.commandOnUpdate) sql += " on update " + command.commandOnUpdate;
    }
    return sql;
  },

  // Each of the column types have their own compiler functions which are
  // responsible for turning the column definition into its SQL format
  // for the platform. Then column modifiers are compiled and added.
  getColumns: function(blueprint) {
    var columns = [];
    for (var i = 0, l = blueprint.columns.length; i < l; i++) {
      var column = blueprint.columns[i];
      var sql = this.wrap(column) + ' ' + this.getType(column, blueprint);
      columns.push(this.addModifiers(sql, blueprint, column));
    }
    return columns;
  },

  // Add the column modifiers to the definition.
  addModifiers: function(sql, blueprint, column) {
    for (var i = 0, l = this.modifiers.length; i < l; i++) {
      var modifier = this.modifiers[i];
      var method = "modify" + modifier;
      if (_.has(this, method)) {
        sql += this[method](blueprint, column) || '';
      }
    }
    return sql;
  },

  // Get the SQL for the column data type.
  getType: function(column, blueprint) {
    return this['type' + Helpers.capitalize(column.type)](column, blueprint);
  },

  // Add a prefix to an array of values, utilized in the client libs.
  prefixArray: function(prefix, values) {
    return _.map(values, function(value) { return prefix + ' ' + value; });
  },

  // Wrap a table in keyword identifiers.
  wrapTable: function(table) {
    if (table instanceof SchemaBuilder) table = table.table;
    return baseGrammar.wrapTable.call(this, table);
  },

  // Wrap a value in keyword identifiers.
  wrap: function(value) {
    if (value && value.name) value = value.name;
    return baseGrammar.wrap.call(this, value);
  },

  // Format a value so that it can be used in "default" clauses.
  getDefaultValue: function(value) {
    if (value instanceof Raw) return value.sql;
    if (value === true || value === false) {
      return parseInt(value, 10);
    }
    return '' + value;
  },

  // Get the primary key command if it exists on the blueprint.
  getCommandByName: function(blueprint, name) {
    var commands = this.getCommandsByName(blueprint, name);
    if (commands.length > 0) return commands[0];
  },

  // Get all of the commands with a given name.
  getCommandsByName: function(blueprint, name) {
    return _.filter(blueprint.commands, function(value) { return value.name == name; }) || [];
  },

  // Used to compile any database specific items.
  compileAdditional: function() {},

  // Compile a create table command.
  compileCreateTable: function(blueprint) {
    var columns = this.getColumns(blueprint).join(', ');
    return 'create table ' + this.wrapTable(blueprint) + ' (' + columns + ')';
  },

  // Compile a drop table command.
  compileDropTable: function(blueprint) {
    return 'drop table ' + this.wrapTable(blueprint);
  },

  // Compile a drop table (if exists) command.
  compileDropTableIfExists: function(blueprint) {
    return 'drop table if exists ' + this.wrapTable(blueprint);
  },

  // Compile a drop index command.
  compileDropIndex: function(blueprint, command) {
    return 'drop index ' + command.index;
  },

  // Default for a biginteger type in database in other databases.
  typeBigInteger: function(column) {
    return this.typeInteger(column);
  },

  // Create the column definition for a string type.
  typeString: function(column) {
    return "varchar(" + column.length + ")";
  },

  // Create the column definition for a text type.
  typeText: function() {
    return 'text';
  },

  // Create the column definition for a tiny integer type.
  typeTinyInteger: function() {
    return 'tinyint';
  },

  // Create the column definition for a time type.
  typeTime: function() {
    return 'time';
  },

  // Create the column definition for a date type.
  typeDate: function() {
    return 'date';
  },

  // Create the column definition for a binary type.
  typeBinary: function() {
    return 'blob';
  },

  // Create the column definition for a json type.
  typeJson: function() {
    return 'text';
  },

  // Create the column definition for a uuid type.
  typeUuid: function() {
    return 'char(36)';
  },

  // Create a specific type
  typeSpecificType: function(column) {
    return column.specific;
  },

  // Get the SQL for a nullable column modifier.
  modifyNullable: function(blueprint, column) {
    if (column.isNullable === false) {
      return ' not null';
    }
  },

  // Get the SQL for a default column modifier.
  modifyDefault: function(blueprint, column) {
    if (column.defaultValue != void 0) {
      return " default '" + this.getDefaultValue(column.defaultValue) + "'";
    }
  }

};