// SQLite3 Query Builder & Compiler

import inherits from 'inherits';
import QueryCompiler from '../../../query/compiler';
import { assign, each, isEmpty, isString, noop, reduce } from 'lodash'

function QueryCompiler_SQLite3(client, builder) {
  QueryCompiler.call(this, client, builder)
}
inherits(QueryCompiler_SQLite3, QueryCompiler)

assign(QueryCompiler_SQLite3.prototype, {

  // The locks are not applicable in SQLite3
  forShare:  emptyStr,

  forUpdate: emptyStr,

  // SQLite requires us to build the multi-row insert as a listing of select with
  // unions joining them together. So we'll build out this list of columns and
  // then join them all together with select unions to complete the queries.
  insert() {
    const insertValues = this.single.insert || []
    let sql = this.with() + `insert into ${this.tableName} `

    if (Array.isArray(insertValues)) {
      if (insertValues.length === 0) {
        return ''
      }
      else if (insertValues.length === 1 && insertValues[0] && isEmpty(insertValues[0])) {
        return sql + this._emptyInsertValue
      }
    } else if (typeof insertValues === 'object' && isEmpty(insertValues)) {
      return sql + this._emptyInsertValue
    }

    const insertData = this._prepInsert(insertValues)

    if (isString(insertData)) {
      return sql + insertData
    }

    if (insertData.columns.length === 0) {
      return '';
    }

    sql += `(${this.formatter.columnize(insertData.columns)})`

    // backwards compatible error
    if (this.client.valueForUndefined !== null) {
      each(insertData.values, bindings => {
        each(bindings, binding => {
          if (binding === undefined) throw new TypeError(
            '`sqlite` does not support inserting default values. Specify ' +
            'values explicitly or use the `useNullAsDefault` config flag. ' +
            '(see docs http://knexjs.org/#Builder-insert).'
          );
        });
      });
    }

    if (insertData.values.length === 1) {
      const parameters = this.formatter.parameterize(
        insertData.values[0], this.client.valueForUndefined
      );
      return sql + ` values (${parameters})`
    }

    const blocks = []
    let i = -1
    while (++i < insertData.values.length) {
      let i2 = -1;
      const block = blocks[i] = [];
      let current = insertData.values[i]
      current = current === undefined ? this.client.valueForUndefined : current
      while (++i2 < insertData.columns.length) {
        block.push(this.formatter.alias(
          this.formatter.parameter(current[i2]),
          this.formatter.wrap(insertData.columns[i2])
        ))
      }
      blocks[i] = block.join(', ')
    }
    return sql + ' select ' + blocks.join(' union all select ')
  },

  // Compile a truncate table statement into SQL.
  truncate() {
    const table = this.tableName
    return {
      sql: `delete from ${table}`,
      output() {
        return this.query({
          sql: `delete from sqlite_sequence where name = ${table}`
        }).catch(noop)
      }
    }
  },

  // Compiles a `columnInfo` query
  columnInfo() {
    const column = this.single.columnInfo
    return {
      sql: `PRAGMA table_info(${this.single.table})`,
      output(resp) {
        const maxLengthRegex = /.*\((\d+)\)/
        const out = reduce(resp, function (columns, val) {
          let { type } = val
          let maxLength = (maxLength = type.match(maxLengthRegex)) && maxLength[1]
          type = maxLength ? type.split('(')[0] : type
          columns[val.name] = {
            type: type.toLowerCase(),
            maxLength,
            nullable: !val.notnull,
            defaultValue: val.dflt_value
          }
          return columns
        }, {})
        return column && out[column] || out
      }
    }
  },

  limit() {
    const noLimit = !this.single.limit && this.single.limit !== 0
    if (noLimit && !this.single.offset) return ''

    // Workaround for offset only,
    // see http://stackoverflow.com/questions/10491492/sqllite-with-skip-offset-only-not-limit
    return `limit ${this.formatter.parameter(noLimit ? -1 : this.single.limit)}`
  }

})

function emptyStr() {
  return ''
}


export default QueryCompiler_SQLite3