// Copyright (C) 2016 Mikael Berthe <mikael@lilotux.net>. All rights reserved.

// Use of this source code is governed by the MIT license,

// which can be found in the LICENSE file.

// Package takuzu provides functions to solve, build or validate takuzu

// puzzles.

package takuzu

import (

	"bytes"

	"fmt"

	"math"

	"github.com/pkg/errors"

)

// Cell is a single cell of a Takuzu game board

type Cell struct {

	Defined bool

	Value   int

}

// Takuzu is a Takuzu game board (Size x Size)

type Takuzu struct {

	Size  int

	Board [][]Cell

}

// New creates a new Takuzu board

func New(size int) Takuzu {

	t := Takuzu{Size: size}

	t.Board = make([][]Cell, size)

	for l := range t.Board {

		t.Board[l] = make([]Cell, size)

	}

	return t

}

// NewFromString creates a new Takuzu board from a string definition

func NewFromString(s string) (*Takuzu, error) {

	l := len(s)

	if l < 4 {

		return nil, errors.New("bad string length")

	}

	size := int(math.Sqrt(float64(l)))

	if size*size != l {

		return nil, errors.New("bad string length")

	}

	i := 0

	t := New(size)

	for line := 0; line < size; line++ {

		for col := 0; col < size; col++ {

			switch s[i] {

			case '0', 'O':

				t.Board[line][col].Defined = true

				t.Board[line][col].Value = 0

			case '1', 'I':

				t.Board[line][col].Defined = true

				t.Board[line][col].Value = 1

			case '.':

			default:

				return nil, errors.New("invalid char in string")

			}

			i++

		}

	}

	return &t, nil

}

// ToString converts a takuzu board to its string representation

func (b Takuzu) ToString() string {

	var sbuf bytes.Buffer

	for line := 0; line < b.Size; line++ {

		for col := 0; col < b.Size; col++ {

			if b.Board[line][col].Defined {

				sbuf.WriteString(fmt.Sprintf("%d", b.Board[line][col].Value))

				continue

			}

			sbuf.WriteByte('.')

		}

	}

	return sbuf.String()

}

// DumpString writes the content of the board as a string

func (b Takuzu) DumpString() {

	fmt.Println(b.ToString())

}

// Clone returns a copy of the Takuzu board

func (b Takuzu) Clone() Takuzu {

	c := New(b.Size)

	for line := range b.Board {

		for col := range b.Board[line] {

			c.Board[line][col] = b.Board[line][col]

		}

	}

	return c

}

// Copy copies a Takuzu board to another existing board

func Copy(src, dst *Takuzu) error {

	if src.Size != dst.Size {

		return errors.New("sizes do not match")

	}

	for line := range src.Board {

		for col := range src.Board[line] {

			dst.Board[line][col] = src.Board[line][col]

		}

	}

	return nil

}

// BoardsMatch compares a Takuzu board to another, optionally ignoring

// empty cells.  Returns true if the two boards match.

func BoardsMatch(t1, t2 *Takuzu, ignoreUndefined bool) (match bool, line, col int) {

	match = true

	if t1 == nil || t2 == nil {

		line, col = -1, -1

		match = false

		return

	}

	if t1.Size != t2.Size {

		line, col = -1, -1

		match = false

		return

	}

	for line = range t1.Board {

		for col = range t1.Board[line] {

			if !t1.Board[line][col].Defined || !t2.Board[line][col].Defined {

				// At least one of the cells is empty

				if ignoreUndefined ||

					!(t1.Board[line][col].Defined || t2.Board[line][col].Defined) {

					// Both cells are empty or we ignore empty cells

					continue

				}

				match = false

				return

			}

			// Both cells are defined

			if t1.Board[line][col].Value != t2.Board[line][col].Value {

				match = false

				return

			}

		}

	}

	line, col = -1, -1

	return

}

// Set sets the value of the cell; a value -1 will set the cell as undefined

func (c *Cell) Set(value int) {

	if value != 0 && value != 1 {

		c.Defined = false

		return

	}

	c.Defined = true

	c.Value = value

}

// Set sets the value of a specific cell

// A value -1 will undefine the cell

func (b Takuzu) Set(l, c, value int) {

	if value != 0 && value != 1 {

		b.Board[l][c].Defined = false

		return

	}

	b.Board[l][c].Defined = true

	b.Board[l][c].Value = value

}

// GetLine returns a slice of cells containing the ith line of the board

func (b Takuzu) GetLine(i int) []Cell {

	return b.Board[i]

}

// GetColumn returns a slice of cells containing the ith column of the board

func (b Takuzu) GetColumn(i int) []Cell {

	c := make([]Cell, b.Size)

	for l := range b.Board {

		c[l] = b.Board[l][i]

	}

	return c

}

// GetLinePointers returns a slice of pointers to the cells of the ith line of the board

func (b Takuzu) GetLinePointers(i int) []*Cell {

	r := make([]*Cell, b.Size)

	for l := range b.Board[i] {

		r[l] = &b.Board[i][l]

	}

	return r

}

// GetColumnPointers returns a slice of pointers to the cells of the ith column of the board

func (b Takuzu) GetColumnPointers(i int) []*Cell {

	r := make([]*Cell, b.Size)

	for l := range b.Board {

		r[l] = &b.Board[l][i]

	}

	return r

}

// FillLineColumn add missing 0s or 1s if all 1s or 0s are there.

// Note: This method can update b.

func (b Takuzu) FillLineColumn(l, c int) {

	fillRange := func(r []*Cell) {

		size := len(r)

		var notFull bool

		var n [2]int

		for x := 0; x < size; x++ {

			if r[x].Defined {

				n[r[x].Value]++

			} else {

				notFull = true

			}

		}

		if !notFull {

			return

		}

		if n[0] == size/2 {

			// Let's fill the 1s

			for _, x := range r {

				if !x.Defined {

					x.Defined = true

					x.Value = 1

				}

			}

		} else if n[1] == size/2 {

			// Let's fill the 0s

			for _, x := range r {

				if !x.Defined {

					x.Defined = true

					x.Value = 0

				}

			}

		}

	}

	var cells []*Cell

	// Fill line

	cells = b.GetLinePointers(l)

	fillRange(cells)

	// Fill column

	cells = b.GetColumnPointers(c)

	fillRange(cells)

}

// DumpBoard displays the Takuzu board

func (b Takuzu) DumpBoard() {

	fmt.Println()

	for i := range b.Board {

		dumpRange(b.Board[i])

	}

}

func dumpRange(cells []Cell) {

	for _, c := range cells {

		if !c.Defined {

			fmt.Printf(". ")

			continue

		}

		fmt.Printf("%d ", c.Value)

	}

	fmt.Println()

}