streamsql/lib/drivers/prototype.js

Streaming SQL ORM

const util = require('util')
const Stream = require('stream')
const sqlstring = require('../sqlstring')

const fmt = util.format.bind(util)

const JOIN_SEP = ':@:'

module.exports = {
  escape: function escape(value) {
    return sqlstring.escape(value)
  },
  escapeId: function escapeId(id) {
    return sqlstring.escapeId(id)
  },
  whereSql: function whereSql(table, conditions) {
    const escape = this.escape
    const escapeId = this.escapeId

    try {
      var sql = build(conditions)
      if (sql) sql = ' WHERE ' + sql
      return sql
    } catch (e) {
      return e;
    }

    function build (conditions) {
      if (!Array.isArray(conditions))
        return generateSql(conditions)

      const groups = conditions.map(function (subset) {
        return '(' + build(subset) + ')'
      })

      // it's unclear as to whether a {} subset query should be
      // included or not - does `get([{id:1}, {}])` return everything,
      // or should the {} be ignored?
      // for now, we're eliminating empty groups
      return groups.join(' OR ').replace(/\s*OR \(\s*\)/, '')
    }

    function generateSql (conditions) {
      const hasConditons = conditions && keys(conditions).length
      if (!hasConditons) return ''

      const clauses = map(conditions, function (val, key) {
        const field = escapeId([table, key].join('.'))
        var cnd = conditions[key]

        if (Array.isArray(cnd)) {
          // if the condition is a simple array,
          // e.g { release_date: [2000,1996] }
          // use an `in` operator.
          if (typeof cnd[0] != 'object') {
            cnd = cnd.map(function (x) { return escape(x) })
            return fmt('%s IN (%s)', field, cnd.join(','))
          }

          return cnd.map(function (subcnd) {
            const operation = subcnd.op || subcnd.operation
            const value = escape(subcnd.value)
            return fmt('%s %s %s', field, operation, value)
          }).join(' AND ')
        }

        if (cnd !== null) {
          if (typeof cnd == 'undefined')
            throw new RangeError('Condition for `'+key+'` cannot be undefined')

          const op = cnd.operation || cnd.op || '='
          if (cnd.value) cnd = cnd.value
          return fmt('%s %s %s', field, op, escape(cnd))
        }

        return fmt('%s IS NULL', field)
      })

      return clauses.join(' AND ')
    }
  },
  orderSql: function orderSql(table, order) {
    if (!order) return ''

    const escape = this.escape
    const escapeId = this.escapeId

    // order can be one of three styles:
    // * implicit ascending, single: 'title'
    // * implicit ascending, multi: ['release_date', 'title']
    // * explicit: { title: 'desc', release_date: 'asc' }

    if (typeof order == 'string') {
      return fmt(' ORDER BY %s ', escapeId(order))
    }

    if (Array.isArray(order))
      return fmt(' ORDER BY %s ', order.map(escapeId).join(','))

    // must be an object
    return fmt(' ORDER BY %s ', map(order, function (value, key) {
      return fmt('%s %s', escapeId(key), value.toUpperCase())
    }).join(','))
  },
  limitSql: function limitSql(limit, page) {
    if (!limit) return ''
    if (!page) return fmt(' LIMIT %s ', limit)
    const beginning = (page - 1) * limit
    return fmt(' LIMIT %s,%s ', beginning, limit)
  },

  selectSql: function selectSql(opts) {
    const escapeId = this.escapeId
    const escape = this.escape
    const table = opts.table
    const tables = opts.tables
    const fields = opts.fields
    const conds = opts.conditions
    const includeFields = opts.include
    const excludeFields = opts.exclude
    const relationships = opts.relationships
    const useRaw = (Array.isArray(conds) && typeof conds[0] === 'string')
                   || typeof conds === 'string'
    const useJoin = (relationships && keys(relationships).length)

    if (useRaw) return rawSql.call(this)
    if (useJoin) return withJoin.call(this)

    const fieldList = filterFields(fields, includeFields, excludeFields)
      .map(escapeId).join(',')

    const clauses = [
      fmt('SELECT %s FROM %s', fieldList, escapeId(table)),
      this.whereSql(table, conds),
      this.orderSql(table, opts.order),
      this.limitSql(opts.limit, opts.page)
    ]

    const error = firstErrorInArray(clauses)
    if (error) return error
    return clauses.join(' ')

    function rawSql() {
      const statementPair = typeof conds == 'string'
       ? [conds, []]
       : conds

      const sql = statementPair[0].replace(/\$table/i, escapeId(table))
      const values = statementPair[1].map(escape)
      const statement = values.reduce(function (sql, value) {
        return sql.replace('?', value)
      }, sql)
      return statement
    }

    function withJoin() {
      var allFields = fields
        .slice().map(function (field) {
          return [table, field].join('.')
        })

      var joinString = ''

      this.normalizeRelationships(table, relationships)

      function addRelationships (relationships, tableAlias) {
        // in the loop below, rel -->
        // { 'type': <string>,
        //   'local': <{table, key}>,
        //   'foreign': <{table, key, [as]}>,
        //   'relationships': <{name*: rel}>,
        //   'optional': <null | boolean>  }

        forEach(relationships, function (rel, name) {
          if (rel.type == 'hasMany') return
          var foreignAs = name
          var localTable = rel.local.table

          rel.foreign.as = tableAlias + JOIN_SEP + foreignAs
          rel.local.table = tableAlias

          allFields = allFields.concat(getFields(rel.foreign, tables))

          joinString += this.joinSql(rel)

          if (rel.relationships)
            addRelationships.call(this, rel.relationships, tableAlias + JOIN_SEP + name)

          rel.foreign.as = foreignAs
          rel.local.table = localTable
        }.bind(this))
      }

      addRelationships.call(this, relationships, table)

      const selectFields =
        filterFields(allFields, includeFields, excludeFields)

      const joinClause =
        fmt('SELECT %s FROM %s %s',
        selectAs(selectFields),
        escapeId(table),
        joinString)

      const clauses = [
        joinClause,
        this.whereSql(table, conds),
        this.orderSql(table, opts.order),
        this.limitSql(opts.limit, opts.page),
      ]

      const error = firstErrorInArray(clauses)
      if (error) return error
      return clauses.join(' ')
    }

    function selectAs(fields) {
      return fields.map(function (field) {
        return fmt(
          '%s AS %s',
          escapeId(field),
          escapeId(field.replace('.', JOIN_SEP)))
      }).join(',')
    }

    function getFields(tableWithAlias, tables) {
      // XXX: probably shouldn't throw
      const name = tableWithAlias.table
      const alias = tableWithAlias.as || name
      const tableDef = tables[name]
      if (!tableDef)
        throw new Error(fmt('table %s is not registered', escapeId(name)))
      return tableDef.fields.map(function (field) {
        return [alias, field].join('.')
      })
    }

  },
  parseJoinRow: function (row, table) {
    const fixed = {}

    forEach(row, function (value, key) {
      const parts = key.split(JOIN_SEP)
      const property = parts.pop()
      var target = fixed
      forEach(parts, function (part) {
        target = (target[part] || (target[part] = {}))
      })
      target[property] = value
    });

    return fixed[table] || {}
  },
  fixHasOne: function (row, opts) {
    const table = opts.table
    const relationships = opts.relationships
    const tableCache = opts.tableCache
    row = this.parseJoinRow(row, table)

    fixRelationships(row, relationships)

    function fixRelationships (target, relationships) {
      forEach(relationships, function (rel, relKey) {
        if (rel.type !== 'hasOne') return
        const foreign = tableCache[rel.foreign.table]
        target[relKey] = new foreign.constructor(target[relKey])

        if (rel.relationships)
          fixRelationships(target[relKey], rel.relationships)
      })
    }

    return row
  },

  fixHasMany: function (globalRow, opts, callback) {
    var globalError
    const table = opts.table
    const tableCache = opts.tableCache
    const hasMany = {}

    findRelationships(opts.relationships)

    if (!keys(hasMany).length)
      return deferCallback(callback, null, globalRow)

    this.normalizeRelationships(table, hasMany)

    var waiting = keys(hasMany).length

    forEach(hasMany, function (rel, relKey) {
      if (globalError) return

      function handleResult (err, rows) {
        if (globalError) return
        if (err) {
          globalError = err
          return callback(err, null)
        }

        const parts = relKey.split('.')
        const property = parts.pop()
        const context = parts.reduce(function (context, part) {
          if (!context[part])
            context[part] = []
          return context[part]
        }, globalRow);

        context[property] = rows.map(function (row) {
          return new rel.foreign.constructor(row)
        })

        return checkDone()
      }

      (rel.via ? fetchVia : fetchDirect)(rel, handleResult);
    })

    function fetchVia (rel, callback) {
      const cond = {}
      const table = tableCache[rel.via.table]
      const options = {relationships: {}}

      options.relationships[rel.foreign.table] = {
        type: 'hasOne',
        local: rel.via.foreign,
        foreign: rel.foreign,
        relationships: rel.relationships || {}
      }

      cond[rel.via.local] = globalRow[rel.local.key]

      table.get(cond, options, function (err, rows) {
        if (err)
          return callback(err);

        return callback(null, rows.map(function (row) {
          return row[rel.foreign.table];
        }));
      })
    }

    function fetchDirect (rel, callback) {
      const cond = {}
      const table = tableCache[rel.foreign.table]
      const options = {relationships: rel.relationships || {}}

      cond[rel.foreign.key] = globalRow[rel.local.key]

      table.get(cond, options, callback)
    }

    function findRelationships (relationships, prefix) {
      prefix = prefix || ''

      forEach(relationships, function (rel, relKey) {
        if (rel.type == 'hasMany')
          hasMany[prefix + relKey] = rel
        if (rel.relationships)
          findRelationships(rel.relationships, prefix + relKey + '.')
      })
    }

    function checkDone() {
      if (globalError) return
      if (--waiting > 0) return
      return callback(null, globalRow)
    }
  },
  hydrateRow: function (row, opts, callback) {
    if (!row || isEmpty(opts.relationships))
      return deferCallback(callback, null, row)

    row = this.fixHasOne(row, {
      table: opts.table,
      relationships: opts.relationships,
      tableCache: opts.tableCache,
    })

    this.fixHasMany(row, {
      table: opts.table,
      relationships: opts.relationships,
      tableCache: opts.tableCache,
    }, callback)
  },
  hydrateRows: function (rows, opts, callback) {
    const results = []
    var waiting = rows.length
    var globalError

    if (!rows.length || isEmpty(opts.relationships))
      return deferCallback(callback, null, rows)

    rows.forEach(function (row, idx) {
      this.hydrateRow(row, opts, function (err, result) {
        if (globalError) return
        if (err) {
          globalError = err
          return callback(err)
        }
        storeResult(result, idx)
      })
    }, this)

    function storeResult(result, pos) {
      results[pos] = result
      if (--waiting > 0) return
      callback(null, results)
    }
  },
  streamHandlers: function (stream, opts) {
    var waiting = 0
    var finishing = false

    const driver = this
    const table = opts.table
    const relationships = opts.relationships
    const tableCache = opts.tableCache
    const RowClass = tableCache[table].constructor

    const withRelationships =
      (relationships && keys(relationships).length)

    function onResult(row) {
      if (!withRelationships) {
        return stream.emit('data', new RowClass(row))
      }

      waiting ++

      // fulfills both hasOne and hasMany relationships
      driver.hydrateRow(row, {
        table: table,
        relationships: relationships,
        tableCache: tableCache,
      }, function (err, row) {
        waiting --
        if (err) return stream.emit(err)
        stream.emit('data', new RowClass(row))
        checkDone()
      })
    }

    function endCallback(err) {
      if (err) return stream.emit('error', err)
      if (waiting > 0) {
        finishing = true
        return false
      }
      stream.emit('end')
    }

    function checkDone() {
      if (finishing && !waiting)
        stream.emit('end')
    }

    return { row: onResult, done: endCallback }

  },
  normalizeRelationships: function (table, relationships) {
    forEach(relationships, function (rel, relKey) {
      if (!rel.local)
        rel.local = { table: table, key: relKey }

      if (typeof rel.local === 'string')
        rel.local = { table: table, key: rel.local }

      if (rel.relationships)
        this.normalizeRelationships(rel.foreign.table, rel.relationships)
    }.bind(this))
    return relationships
  },

  joinSql: function (opts) {
    // opts --> <see `withJoin` above>
    const local = opts.local
    const foreign = opts.foreign
    const joinType = opts.optional ? ' LEFT ' : ' INNER '
    const localKey = fmt('%s.%s', local.table, local.key)
    const foreignTableAlias = foreign.as || foreign.table
    const foreignKey = fmt('%s.%s', foreignTableAlias, foreign.key)

    const statement = joinType
      + ' JOIN ' + this.escapeId(foreign.table)
      + ' AS '   + this.escapeId(foreignTableAlias)
      + ' ON '   + this.escapeId(localKey)
      + ' = '    + this.escapeId(foreignKey)

    return statement
  },
  insertSql: function insertSql(table, row) {
    const columns = keys(row)
    const values = vals(row)

    const tpl = 'INSERT INTO %s (%s) VALUES (%s)'
    return fmt(tpl, this.escapeId(table),
               map(columns, this.escapeId),
               map(values, this.escape))
  },
  updateSql: function updateSql(table, row, conds) {
    const escape = this.escape
    const escapeId = this.escapeId
    const pairs = map(row, function (val, col) {
      return fmt('%s = %s', escapeId(col), escape(val))
    })
    return fmt('UPDATE %s SET %s %s',
               escapeId(table),
               pairs.join(','),
               this.whereSql(table, conds))
  },
  deleteSql: function deleteSql(opts) {
    const table = opts.table
    const conds = opts.conditions
    const limit = opts.limit

    const clauses = [
      fmt('DELETE FROM %s', this.escapeId(table)),
      this.whereSql(table, conds),
      this.limitSql(limit),
    ]

    const error = firstErrorInArray(clauses)
    if (error) return error
    return clauses.join(' ')
  },
}

function appearsLast(string, sub) {
  const index = string.indexOf(sub)
  if (index == -1) return false
  return string.slice(index) == sub
}

function filterFields(fields, includeFields, excludeFields) {
  if (!includeFields && !excludeFields)
    return fields

  // we always include ids because they are needed for proper
  // relationship fulfillment
  if (includeFields)
    includeFields.push('id')

  return fields.filter(function (field) {
    function search(needle) {
      return appearsLast(field, needle)
    }
    if (includeFields)
      return includeFields.some(search)
    if (excludeFields)
      return !excludeFields.some(search)
    return field
  })
}

function map(obj, fn) {
  return Object.keys(obj).map(function (key) {
    return fn(obj[key], key)
  })
}

function forEach(obj, fn) {
  return Object.keys(obj).forEach(function (key) {
    fn(obj[key], key)
  })
}

function keys(o) {
  return Object.keys(o)
}

function vals(o) {
  return map(o, function (val) { return val })
}

function isEmpty(obj) {
  return (!obj || !keys(obj).length)
}

function deferCallback(callback, err, arg) {
  return setImmediate(function () {
    callback(null, arg)
  })
}

const errorRegExp = /Error$/
function isError(thing) {
  return (typeof thing == 'object' && errorRegExp.exec(thing.name))
}

function firstErrorInArray(array) {
  for (var idx = 0, item; idx < array.length; idx++) {
    item = array[idx]
    if (isError(item)) return item
  }
  return null
}