// Copyright 2014 by Sascha L. Teichmann
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.

package main

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"log"
	"strconv"
)

type RedisConsumer interface {
	ConsumeInteger(int64) bool
	ConsumeArray(int64) bool
	ConsumeSimpleString(string) bool
	ConsumeBulkString([]byte) bool
	ConsumeError(error) bool
}

type RedisParser struct {
	reader   *bufio.Reader
	consumer RedisConsumer
}

func NewRedisParser(reader *bufio.Reader, consumer RedisConsumer) *RedisParser {
	return &RedisParser{
		reader:   reader,
		consumer: consumer}
}

func (rp *RedisParser) Parse() {
	for line := rp.nextLine(); line != nil && rp.dispatch(line); line = rp.nextLine() {
	}
}

func (rp *RedisParser) nextLine() []byte {
	line, err := rp.reader.ReadBytes('\n')
	if err != nil {
		if err != io.EOF {
			rp.consumer.ConsumeError(err)
		}
		return nil
	}
	return bytes.TrimRight(line, "\r\n")
}

func (rp *RedisParser) dispatch(line []byte) bool {
	if len(line) < 1 {
		return false
	}
	switch line[0] {
	case '-':
		return true // ignore errors
	case ':':
		return rp.integer(line)
	case '+':
		return rp.simpleString(line)
	case '$':
		return rp.bulkString(line)
	case '*':
		return rp.array(line)
	}
	return true
}

func (rp *RedisParser) simpleString(line []byte) bool {
	return rp.consumer.ConsumeSimpleString(string(line[1:]))
}

func (rp *RedisParser) integer(line []byte) bool {
	i, err := strconv.ParseInt(string(line[1:]), 10, 64)
	if err != nil {
		return rp.consumer.ConsumeError(err)
	}
	return rp.consumer.ConsumeInteger(i)
}

func (rp *RedisParser) bulkString(line []byte) bool {
	var i int64
	var err error
	i, err = strconv.ParseInt(string(line[1:]), 10, 64)
	if err != nil {
		return rp.consumer.ConsumeError(err)
	}
	switch {
	case i < 0:
		return rp.consumer.ConsumeBulkString(nil)
	case i == 0:
		return rp.consumer.ConsumeBulkString([]byte{})
	default:
		data := make([]byte, i, i)
		var n int
		if n, err = rp.reader.Read(data); err != nil {
			return rp.consumer.ConsumeError(err)
		}
		if _, err = rp.reader.ReadBytes('\n'); err != nil {
			return rp.consumer.ConsumeError(err)
		}
		return rp.consumer.ConsumeBulkString(data[0:n])
	}
}

func (rp *RedisParser) array(line []byte) bool {
	var i int64
	var err error
	i, err = strconv.ParseInt(string(line[1:]), 10, 64)
	if err != nil {
		return rp.consumer.ConsumeError(err)
	}
	return rp.consumer.ConsumeArray(i)
}

type RedisCommands interface {
	Hget(hash, key []byte) bool
	Hset(hash, key, block []byte) bool
	Multi() bool
	Exec() bool
}

type RedisCommandExecutor struct {
	commands RedisCommands
	missing  int64
	args     []interface{}
}

func NewRedisCommandExecutor(commands RedisCommands) *RedisCommandExecutor {
	return &RedisCommandExecutor{
		commands: commands,
		missing:  0,
		args:     []interface{}{}}
}

func (rce *RedisCommandExecutor) push(i interface{}) bool {
	rce.args = append(rce.args, i)
	rce.missing--
	if rce.missing <= 0 {
		rce.missing = 0
		res := rce.execute()
		rce.args = []interface{}{}
		return res
	}
	return true
}

func asString(i interface{}) string {
	switch i.(type) {
	case string:
		return i.(string)
	case []byte:
		return string(i.([]byte))
	}
	return fmt.Sprintf("%s", i)
}

func (rce *RedisCommandExecutor) execute() bool {
	l := len(rce.args)
	if l < 1 {
		log.Printf("WARN: Too less argument for command.")
		return false
	}
	cmd := asString(rce.args[0])
	switch cmd {
	case "HGET":
		if l < 3 {
			log.Println("WARN: Missing argments for HGET.")
			return false
		}
		hash, ok1 := rce.args[1].([]byte)
		key, ok2 := rce.args[2].([]byte)
		if !ok1 || !ok2 {
			log.Println("WARN: HGET data are not byte slices.")
			return false
		}
		return rce.commands.Hget(hash, key)

	case "HSET":
		if l < 4 {
			log.Println("WARN: Missing argments for HSET.")
			return false
		}
		hash, ok1 := rce.args[1].([]byte)
		key, ok2 := rce.args[2].([]byte)
		value, ok3 := rce.args[3].([]byte)

		if !ok1 || !ok2 || !ok3 {
			log.Println("WARN: HSET data are not byte slices.")
			return false
		}
		return rce.commands.Hset(hash, key, value)

	case "MULTI":
		return rce.commands.Multi()

	case "EXEC":
		return rce.commands.Exec()
	}
	log.Printf("WARN: unknown command: '%s'\n", cmd)
	return false
}

func (rce *RedisCommandExecutor) ConsumeSimpleString(s string) bool {
	return rce.push(s)
}

func (rce *RedisCommandExecutor) ConsumeBulkString(data []byte) bool {
	return rce.push(data)
}

func (rce *RedisCommandExecutor) ConsumeInteger(i int64) bool {
	return rce.push(i)
}

func (rce *RedisCommandExecutor) ConsumeError(err error) bool {
	log.Printf("error: %s", err)
	return true
}

func (rce *RedisCommandExecutor) ConsumeArray(i int64) bool {
	if rce.missing > 0 {
		log.Println("WARN: Nested arrays are not supported!")
		return false
	}
	if i < 0 {
		log.Println("Null arrays are not supported")
		return false
	}
	rce.missing = i
	return true
}