// vi:ts=4:sts=4:sw=4:noet:tw=72

package modules

// This Markov chain code is taken from the "Generating arbitrary text"
// codewalk: http://golang.org/doc/codewalk/markov/
//
// Minor modifications have been made to make it easier to integrate
// with a webserver and to save/load state

import (
	"bufio"
	"encoding/gob"
	"fmt"
	"math/rand"
	"os"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"

	"code.dnix.de/an/xlog"

	"github.com/sorcix/irc"
)

var markovChain *MarkovChain

func init() {
	MsgFuncs["markov"] = markovHandleMessage
	RunFuncs["markov"] = markovRun
}

func markovHandleMessage(m *irc.Message) {
	text := m.Trailing
	if text == "" {
		return
	}

	text = markovParseText(text)

	markovChain.Write(text)

	answerLen, _ := strconv.Atoi(ModParams["markov-answer-len"])
	respChance, _ := strconv.Atoi(ModParams["markov-response-chance"])
	if rand.Intn(100) <= respChance || strings.HasPrefix(text, ModParams["_nick"]) {
		responseText := markovChain.Generate(answerLen, text)
		if responseText != "" {
			go func() {
				time.Sleep(time.Duration(rand.Intn(8)+2) * time.Second)
				SayCh <- "*\n" + responseText
			}()
		}
	}
}

func markovRun() {
	prefixLen, _ := strconv.Atoi(ModParams["markov-prefix-len"])
	markovChain = markovNewChain(prefixLen)
	//if *importFile != "" {
	//	StartImport(*importFile)
	filepath := ModParams["markov-import-file"]
	if filepath != "-" {
		file, _ := os.Open(filepath)
		scanner := bufio.NewScanner(file)
		for scanner.Scan() {
			text := scanner.Text()
			text = markovParseText(text)
			if text != "" {
				markovChain.Write(text)
			}
		}
	} else {
		err := markovChain.Load(ModParams["markov-state-file"])
		if err != nil {
			xlog.Error(err.Error())
		}
	}
	go func() {
		for {
			time.Sleep(60 * time.Second)
			markovChain.Save(ModParams["markov-state-file"])
		}
	}()

}

func markovParseText(text string) string {
	messageRegex := regexp.MustCompile(`<([^>]+)>`)
	matches := messageRegex.FindAllStringSubmatch(text, -1)
	for _, matches2 := range matches {

		if strings.HasPrefix(matches2[1], "http") || strings.HasPrefix(matches2[1], "mailto") {
			text = strings.Replace(text, matches2[0], "", -1)

		} else if strings.HasPrefix(matches2[1], "@U") {
			parts := strings.SplitN(matches2[1], "|", 2)

			if len(parts) == 2 {
				text = strings.Replace(text, matches2[0], "@"+parts[1], -1)
			} else {
				text = strings.Replace(text, matches2[0], "", -1)
			}

		} else if strings.HasPrefix(matches2[1], "@") {
			text = strings.Replace(text, matches2[0], matches2[1], -1)

		} else if strings.HasPrefix(matches2[1], "#") {
			parts := strings.SplitN(matches2[1], "|", 2)

			if len(parts) == 2 {
				text = strings.Replace(text, matches2[0], "#"+parts[1], -1)
			} else {
				text = strings.Replace(text, matches2[0], "", -1)
			}

		}
	}

	text = strings.TrimSpace(text)

	text = strings.Replace(text, "&lt;", "<", -1)
	text = strings.Replace(text, "&gt;", ">", -1)
	text = strings.Replace(text, "&amp;", "&", -1)

	return text
}

// Prefix is a Markov chain prefix of one or more words.
type MarkovPrefix []string

// String returns the Prefix as a string (for use as a map key).
func (p MarkovPrefix) String() string {
	return strings.Join(p, " ")
}

// Shift removes the first word from the Prefix and appends the given word.
func (p MarkovPrefix) Shift(word string) {
	copy(p, p[1:])
	p[len(p)-1] = word
}

// MarkovChain contains a map ("chain") of prefixes to a list of suffixes.
// A prefix is a string of prefixLen words joined with spaces.
// A suffix is a single word. A prefix can have multiple suffixes.
type MarkovChain struct {
	MarkovChain map[string][]string
	prefixLen   int
	mu          sync.Mutex
}

// NewMarkovChain returns a new MarkovChain with prefixes of prefixLen words.
func markovNewChain(prefixLen int) *MarkovChain {
	return &MarkovChain{
		MarkovChain: make(map[string][]string),
		prefixLen:   prefixLen,
	}
}

// Write parses the bytes into prefixes and suffixes that are stored in MarkovChain.
func (c *MarkovChain) Write(in string) (int, error) {
	in = strings.ToLower(in)
	sr := strings.NewReader(in)
	p := make(MarkovPrefix, c.prefixLen)
	for {
		var s string
		if _, err := fmt.Fscan(sr, &s); err != nil {
			break
		}
		key := p.String()
		c.mu.Lock()
		c.MarkovChain[key] = append(c.MarkovChain[key], s)
		c.mu.Unlock()
		p.Shift(s)
	}
	return len(in), nil
}

// Generate returns a string of at most n words generated from MarkovChain.
func (c *MarkovChain) Generate(n int, in string) string {
	in = strings.ToLower(in)
	c.mu.Lock()
	defer c.mu.Unlock()
	p := make(MarkovPrefix, c.prefixLen)
	p = strings.Split(in, " ")
	for {
		if len(p) == c.prefixLen {
			break
		}
		if len(p) < c.prefixLen {
			p = append(p, "")
		}
		if len(p) > c.prefixLen {
			if rand.Intn(2) == 0 {
				p = p[1:]
			} else {
				p = p[0 : len(p)-1]
			}
		}
	}
	prefix := p.String()
	var words []string
	for i := 0; i < n; i++ {
		choices := c.MarkovChain[p.String()]
		if len(choices) == 0 {
			break
		}
		next := choices[rand.Intn(len(choices))]
		words = append(words, next)
		p.Shift(next)
	}
	if len(words) == 0 {
		return ""
	} else {
		return prefix + " " + strings.Join(words, " ")
	}
}

// Save the chain to a file
func (c *MarkovChain) Save(fileName string) error {
	// Open the file for writing
	fo, err := os.Create(fileName)
	if err != nil {
		return err
	}
	// close fo on exit and check for its returned error
	defer func() {
		if err := fo.Close(); err != nil {
			panic(err)
		}
	}()

	// Create an encoder and dump to it
	c.mu.Lock()
	defer c.mu.Unlock()

	enc := gob.NewEncoder(fo)
	err = enc.Encode(c)
	if err != nil {
		return err
	}

	return nil
}

// Load the chain from a file
func (c *MarkovChain) Load(fileName string) error {
	// Open the file for reading
	fi, err := os.Open(fileName)
	if err != nil {
		return err
	}
	// close fi on exit and check for its returned error
	defer func() {
		if err := fi.Close(); err != nil {
			panic(err)
		}
	}()

	// Create a decoder and read from it
	c.mu.Lock()
	defer c.mu.Unlock()

	dec := gob.NewDecoder(fi)
	err = dec.Decode(c)
	if err != nil {
		return err
	}

	return nil
}