const { pushQuery, pushAdditional, unshiftQuery } = require('./helpers');

const { isUndefined } = require('lodash');

// The "SchemaCompiler" takes all of the query statements which have been
// gathered in the "SchemaBuilder" and turns them into an array of
// properly formatted / bound query strings.
function SchemaCompiler(client, builder) {
  this.builder = builder;
  this._commonBuilder = this.builder;
  this.client = client;
  this.schema = builder._schema;
  this.formatter = client.formatter(builder);
  this.sequence = [];
}

function throwOnlyPGError(operationName) {
  throw new Error(
    `${operationName} is not supported for this dialect (only PostgreSQL supports it currently).`
  );
}

Object.assign(SchemaCompiler.prototype, {
  pushQuery: pushQuery,

  pushAdditional: pushAdditional,

  unshiftQuery: unshiftQuery,

  createTable: buildTable('create'),

  createTableIfNotExists: buildTable('createIfNot'),

  createSchema: () => {
    throwOnlyPGError('createSchema');
  },
  createSchemaIfNotExists: () => {
    throwOnlyPGError('createSchemaIfNotExists');
  },
  dropSchema: () => {
    throwOnlyPGError('dropSchema');
  },
  dropSchemaIfExists: () => {
    throwOnlyPGError('dropSchemaIfExists');
  },

  alterTable: buildTable('alter'),

  dropTablePrefix: 'drop table ',

  dropTable(tableName) {
    this.pushQuery(
      this.dropTablePrefix +
        this.formatter.wrap(prefixedTableName(this.schema, tableName))
    );
  },

  dropTableIfExists(tableName) {
    this.pushQuery(
      this.dropTablePrefix +
        'if exists ' +
        this.formatter.wrap(prefixedTableName(this.schema, tableName))
    );
  },

  raw(sql, bindings) {
    this.sequence.push(this.client.raw(sql, bindings).toSQL());
  },

  toSQL() {
    const sequence = this.builder._sequence;
    for (let i = 0, l = sequence.length; i < l; i++) {
      const query = sequence[i];
      this[query.method].apply(this, query.args);
    }
    return this.sequence;
  },
});

function buildTable(type) {
  return function(tableName, fn) {
    const builder = this.client.tableBuilder(type, tableName, fn);

    // pass queryContext down to tableBuilder but do not overwrite it if already set
    const queryContext = this.builder.queryContext();
    if (!isUndefined(queryContext) && isUndefined(builder.queryContext())) {
      builder.queryContext(queryContext);
    }

    builder.setSchema(this.schema);
    const sql = builder.toSQL();

    for (let i = 0, l = sql.length; i < l; i++) {
      this.sequence.push(sql[i]);
    }
  };
}

function prefixedTableName(prefix, table) {
  return prefix ? `${prefix}.${table}` : table;
}

module.exports = SchemaCompiler;