package datokenizer

/**
 * The file reader is basically a port of foma2js,
 * licensed under the Apache License, version 2,
 * and written by Mans Hulden.
 */

// TODO:
// - replace maxSize with the check value
// - Strip first state and make everything start with 0!
// - Serialize!
// - Split Tokenizer and DATokenizer

import (
	"bufio"
	"compress/gzip"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
	"unicode/utf8"

	"github.com/rs/zerolog/log"
)

const (
	PROPS   = 1
	SIGMA   = 2
	STATES  = 3
	NONE    = 4
	NEWLINE = '\u000a'
	DEBUG   = false
)

// Special symbols in sigma
var EPSILON = -1
var UNKNOWN = -1
var IDENTITY = -1
var FINAL = -1

type mapping struct {
	source int
	target int
}

type edge struct {
	inSym  int
	outSym int
	end    int
}

type Tokenizer struct {
	sigma       map[rune]int
	sigmaRev    map[int]rune
	arcCount    int
	stateCount  int
	sigmaCount  int
	maxSize     int
	array       []int
	transitions []map[int]*edge
}

func ParseFile(file string) *Tokenizer {
	f, err := os.Open(file)
	if err != nil {
		log.Error().Err(err)
		os.Exit(0)
	}
	defer f.Close()

	gz, err := gzip.NewReader(f)
	if err != nil {
		log.Error().Err(err)
		os.Exit(0)
	}
	defer gz.Close()

	return Parse(gz)
}

func Parse(ior io.Reader) *Tokenizer {
	r := bufio.NewReader(ior)

	tok := &Tokenizer{
		sigma:    make(map[rune]int),
		sigmaRev: make(map[int]rune),
	}

	var state, inSym, outSym, end, final int

	mode := 0
	var elem []string
	var elemint [5]int

	for {
		line, err := r.ReadString('\n')
		if err != nil {
			if err == io.EOF {
				break
			}
			log.Error().Err(err)
			os.Exit(0)
		}
		if strings.HasPrefix(line, "##foma-net") {
			continue
		}
		if strings.HasPrefix(line, "##props##") {
			mode = PROPS
			continue
		}
		if strings.HasPrefix(line, "##states##") {
			mode = STATES

			// Adds a final transition symbol to sigma
			// written as '#' in Mizobuchi et al (2000)
			tok.sigmaCount++
			FINAL = tok.sigmaCount
			continue
		}
		if strings.HasPrefix(line, "##sigma##") {
			mode = SIGMA
			continue
		}
		if strings.HasPrefix(line, "##end##") {
			mode = NONE
			continue
		}

		switch mode {
		case PROPS:
			{
				elem = strings.Split(line, " ")
				/*
					fmt.Println("arity:            " + elem[0])
					fmt.Println("arccount:         " + elem[1])
					fmt.Println("statecount:       " + elem[2])
					fmt.Println("linecount:        " + elem[3])
					fmt.Println("finalcount:       " + elem[4])
					fmt.Println("pathcount:        " + elem[5])
					fmt.Println("is_deterministic: " + elem[6])
					fmt.Println("is_pruned:        " + elem[7])
					fmt.Println("is_minimized:     " + elem[8])
					fmt.Println("is_epsilon_free:  " + elem[9])
					fmt.Println("is_loop_free:     " + elem[10])
					fmt.Println("extras:           " + elem[11])
					fmt.Println("name:             " + elem[12])
				*/
				if elem[6] != "1" {
					log.Error().Msg("The FST needs to be deterministic")
					os.Exit(1)
				}
				if elem[9] != "1" {
					log.Error().Msg("The FST needs to be epsilon free")
					os.Exit(1)
				}

				elemint[0], err = strconv.Atoi(elem[1])
				if err != nil {
					log.Error().Msg("Can't read arccount")
					os.Exit(1)
				}
				tok.arcCount = elemint[0]

				// States start at 1 in Mizobuchi et al (2000),
				// as the state 0 is associated with a fail.
				// Initialize states and transitions
				elemint[0], err = strconv.Atoi(elem[2])
				if err != nil {
					log.Error().Msg("Can't read statecount")
					os.Exit(1)
				}
				tok.stateCount = elemint[0]
				tok.transitions = make([]map[int]*edge, elemint[0]+1)
				continue
			}
		case STATES:
			{
				elem = strings.Split(line[0:len(line)-1], " ")
				if elem[0] == "-1" {
					continue
				}
				elemint[0], err = strconv.Atoi(elem[0])
				if err != nil {
					break
				}

				if len(elem) > 1 {
					elemint[1], err = strconv.Atoi(elem[1])
					if err != nil {
						break
					}
					if len(elem) > 2 {
						elemint[2], err = strconv.Atoi(elem[2])
						if err != nil {
							break
						}
						if len(elem) > 3 {
							elemint[3], err = strconv.Atoi(elem[3])
							if err != nil {
								break
							}
							if len(elem) > 4 {
								elemint[4], err = strconv.Atoi(elem[4])
								if err != nil {
									break
								}
							}
						}
					}
				}

				switch len(elem) {
				case 5:
					{
						state = elemint[0]
						inSym = elemint[1]
						outSym = elemint[2]
						end = elemint[3]
						final = elemint[4]
					}
				case 4:
					{
						if elemint[1] == -1 {
							state = elemint[0]
							final = elemint[3]
						} else {
							state = elemint[0]
							inSym = elemint[1]
							end = elemint[2]
							final = elemint[3]
							outSym = inSym
						}
					}
				case 3:
					{
						inSym = elemint[0]
						outSym = elemint[1]
						end = elemint[2]
					}
				case 2:
					{
						inSym = elemint[0]
						end = elemint[1]
						outSym = inSym
					}
				}

				// While the states in foma start with 0, the states in the
				// Mizobuchi FSA start with one - so we increase every state by 1.

				if inSym != outSym {

					// Allow any epsilon to become a newline
					if !(inSym == EPSILON && tok.sigmaRev[outSym] == NEWLINE) &&

						// Allow any whitespace to be ignored
						!(inSym != EPSILON && outSym == EPSILON) &&

						// Allow any whitespace to become a new line
						!(tok.sigmaRev[outSym] == NEWLINE) {

						log.Error().Msg(
							"Unsupported transition: " +
								strconv.Itoa(state) +
								" -> " + strconv.Itoa(end) +
								" (" +
								strconv.Itoa(inSym) +
								":" +
								strconv.Itoa(outSym) +
								") (" +
								string(tok.sigmaRev[inSym]) +
								":" +
								string(tok.sigmaRev[outSym]) +
								")")
						os.Exit(1)
					}
				}

				// This collects all edges until arrstate changes

				// TODO:
				//   if arrin == EPSILON && arrout == TOKENEND, mark state as newline
				//   if the next transition is the same, remove TOKENEND and add SENTENCEEND
				//   This requires to remove the transition alltogether and marks the state instead.

				// TODO:
				//   if arrout == EPSILON, mark the transition as NOTOKEN

				targetObj := &edge{
					inSym:  inSym,
					outSym: outSym,
					end:    end + 1,
				}

				// Initialize outgoing states
				if tok.transitions[state+1] == nil {
					tok.transitions[state+1] = make(map[int]*edge)
				}

				// Ignore transitions with invalid symbols
				if inSym >= 0 {
					tok.transitions[state+1][inSym] = targetObj
				}

				// Add final transition
				if final == 1 {
					tok.transitions[state+1][FINAL] = &edge{}
				}

				if DEBUG {
					fmt.Println("Add",
						state+1, "->", end+1,
						"(",
						inSym,
						":",
						outSym,
						") (",
						string(tok.sigmaRev[inSym]),
						":",
						string(tok.sigmaRev[outSym]),
						")")
				}

				continue
			}
		case SIGMA:
			{
				elem = strings.SplitN(line[0:len(line)-1], " ", 2)

				// Turn string into sigma id
				number, err := strconv.Atoi(elem[0])

				if err != nil {
					log.Error().Err(err)
					os.Exit(0)
				}

				tok.sigmaCount = number

				var symbol rune

				// Read rune
				if utf8.RuneCountInString(elem[1]) == 1 {
					symbol = []rune(elem[1])[0]

					// Probably a MCS
				} else if utf8.RuneCountInString(elem[1]) > 1 {
					switch elem[1] {
					case "@_EPSILON_SYMBOL_@":
						{
							EPSILON = number
							continue
						}
					case "@_UNKNOWN_SYMBOL_@":
						{
							UNKNOWN = number
							continue
						}

					case "@_IDENTITY_SYMBOL_@":
						{
							IDENTITY = number
							continue
						}
					default:
						{
							log.Error().Msg("MCS not supported: " + line)
							os.Exit(1)
						}
					}

				} else { // Probably a new line symbol
					line, err = r.ReadString('\n')
					if err != nil {
						log.Error().Err(err)
						os.Exit(0)
					}
					if len(line) != 1 {
						log.Error().Msg("MCS not supported:" + line)
						os.Exit(0)
					}
					symbol = rune(NEWLINE)
				}

				tok.sigma[symbol] = number
				tok.sigmaRev[number] = symbol
			}
		}
	}

	return tok
}

// Implementation of Mizobuchi et al (2000), p.128
func (tok *Tokenizer) ToDoubleArray() *Tokenizer {

	mark := 0
	size := 0

	// Create a mapping from s to t
	table := make([]*mapping, tok.arcCount+1)

	table[size] = &mapping{source: 1, target: 1}
	size++

	// Allocate space for the outgoing symbol range
	A := make([]int, 0, tok.sigmaCount)

	for mark < size {
		s := table[mark].source // This is a state in Ms
		t := table[mark].target // This is a state in Mt
		mark++

		// Following the paper, here the state t can be remembered
		// in the set of states St
		A = A[:0]
		tok.get_set(s, &A)

		// Set base to the first free slot in the double array
		tok.setBase(t, tok.xCheck(A))

		// Iterate over all outgoing symbols
		for _, a := range A {

			if a != FINAL {

				// Aka g(s, a)
				s1 := tok.transitions[s][a].end

				// Store the transition
				t1 := tok.getBase(t) + a
				tok.setCheck(t1, t)

				// Check for representative states
				r := in_table(s1, table, size)

				if r == 0 {
					// Remember the mapping
					table[size] = &mapping{source: s1, target: t1}
					size++
				} else {
					// Overwrite with the representative state
					tok.setBase(t1, -1*r)
				}
			} else {
				// Store a final transition
				tok.setCheck(tok.getBase(t)+FINAL, t)
			}
		}
	}

	// Following Mizobuchi et al (2000) the size of the
	// FSA should be stored in check(1).
	tok.setCheck(1, tok.maxSize+1)
	tok.array = tok.array[:tok.maxSize+1]
	return tok
}

// Resize double array when necessary
func (tok *Tokenizer) resize(l int) {
	// TODO:
	//   This is a bit too aggressive atm and should be calmed down.
	if len(tok.array) <= l {
		tok.array = append(tok.array, make([]int, l)...)
	}
}

// Set base value in double array
func (tok *Tokenizer) setBase(p int, v int) {
	l := p*2 + 1
	tok.resize(l)
	if tok.maxSize < l {
		tok.maxSize = l
	}
	tok.array[p*2] = v
}

// Get base value in double array
func (tok *Tokenizer) getBase(p int) int {
	if p*2 >= len(tok.array) {
		return 0
	}
	return tok.array[p*2]
}

// Set check value in double array
func (tok *Tokenizer) setCheck(p int, v int) {
	l := p*2 + 1
	tok.resize(l)
	if tok.maxSize < l {
		tok.maxSize = l
	}
	tok.array[(p*2)+1] = v
}

// Get check value in double array
func (tok *Tokenizer) getCheck(p int) int {
	if (p*2)+1 >= len(tok.array) {
		return 0
	}
	return tok.array[(p*2)+1]
}

// Set size of double array
func (tok *Tokenizer) setSize(p, v int) {
	tok.setCheck(1, v)
}

// Get size of double array
func (tok *Tokenizer) getSize(p int) int {
	return tok.getCheck(1)
}

// Check the table if a mapping of s
// exists and return this as a representative.
// Currently iterates through the whole table
// in a bruteforce manner.
func in_table(s int, table []*mapping, size int) int {
	for x := 0; x < size; x++ {
		if table[x].source == s {
			return table[x].target
		}
	}
	return 0
}

// Set alphabet A to the list of all symbols
// outgoing from s
func (tok *Tokenizer) get_set(s int, A *[]int) {
	for a := range tok.transitions[s] {
		*A = append(*A, a)
	}
}

// Based on Mizobuchi et al (2000), p. 124
// This iterates for every state through the complete double array
// structure until it finds a gap that fits all outgoing transitions
// of the state. This is extremely slow, but is only necessary in the
// construction phase of the tokenizer.
func (tok *Tokenizer) xCheck(symbols []int) int {

	// Start at the first entry of the double array list
	base := 1

OVERLAP:

	// Resize the array if necessary
	tok.resize((base + FINAL) * 2)
	for _, a := range symbols {
		if tok.getCheck(base+a) != 0 {
			base++
			goto OVERLAP
		}
	}
	return base
}

// Match an input string against the double array
// FSA.
//
// Based on Mizobuchi et al (2000), p. 129,
// with additional support for IDENTITY, UNKNOWN
// and EPSILON transitions.
func (tok *Tokenizer) Match(input string) bool {
	var a int
	var tu int
	var ok bool

	t := 1 // Initial state
	chars := []rune(input)
	i := 0

	for i < len(chars) {
		a, ok = tok.sigma[chars[i]]

		// Support identity symbol if character is not in sigma
		if !ok && IDENTITY != -1 {
			if DEBUG {
				fmt.Println("IDENTITY symbol", string(chars[i]), "->", IDENTITY)
			}
			a = IDENTITY
		} else if DEBUG {
			fmt.Println("Sigma transition is okay for [", string(chars[i]), "]")
		}
		tu = t
	CHECK:
		t = tok.getBase(tu) + a

		// Check if the transition is valid according to the double array
		if t > tok.getCheck(1) || tok.getCheck(t) != tu {

			if DEBUG {
				fmt.Println("Match is not fine!", t, "and", tok.getCheck(t), "vs", tu)
			}

			if !ok && a == IDENTITY {
				// Try again with unknown symbol, in case identity failed
				if DEBUG {
					fmt.Println("UNKNOWN symbol", string(chars[i]), "->", UNKNOWN)
				}
				a = UNKNOWN

			} else if a != EPSILON {
				// Try again with epsilon symbol, in case everything else failed
				if DEBUG {
					fmt.Println("EPSILON symbol", string(chars[i]), "->", EPSILON)
				}
				a = EPSILON
			} else {
				break
			}
			goto CHECK
		} else if tok.getBase(t) < 0 {
			// Move to representative state
			t = -1 * tok.getBase(t)
		}

		// Transition is fine
		if a != EPSILON {
			// Character consumed
			i++
		}
		// TODO:
		//   Prevent endless epsilon loops!
	}

	if i != len(chars) {
		if DEBUG {
			fmt.Println("Not at the end")
		}
		return false
	}

FINALCHECK:

	// Automaton is in a final state
	if tok.getCheck(tok.getBase(t)+FINAL) == t {
		return true
	}

	// Check epsilon transitions until a final state is reached
	tu = t
	a = EPSILON
	t = tok.getBase(tu) + a

	// Epsilon transition failed
	if t > tok.getCheck(1) || tok.getCheck(t) != tu {
		if DEBUG {
			fmt.Println("Match is not fine!", t, "and", tok.getCheck(t), "vs", tu)
		}
		return false

	} else if tok.getBase(t) < 0 {
		// Move to representative state
		t = -1 * tok.getBase(t)
	}

	goto FINALCHECK
}