package board

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"math/rand"
	"time"
)

type Board struct {
	Cols   int        `json:"cols"`
	Rows   int        `json:"rows"`
	Finish Coordinate `json:"finish"`
	Tiles  []Tile     `json:"-"`
}

const maxIceWidth = 26

// Create a new randomly generated board.
func New(cols, rows int) *Board {
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	return new(cols, rows, r)
}

func new(cols, rows int, r *rand.Rand) *Board {
	b := &Board{
		Cols:  cols,
		Rows:  rows,
		Tiles: make([]Tile, rows*cols, rows*cols)}

	for y := 0; y < rows; y++ {
		for x := 0; x < cols; x++ {
			switch {
			case r.Intn(10) > 7:
				b.Set(x, y, Rock)
			case x > (b.Cols-maxIceWidth)/2 && x < b.Cols/2+maxIceWidth/2 && r.Intn(maxIceWidth) >= abs((b.Cols/2)-x):
				b.Set(x, y, Ice)
			default:
				b.Set(x, y, Water)
			}
		}
	}

	igloY := r.Intn(rows-2) + 1

	b.Set(cols-2, igloY, Iglo)
	b.Finish.X = cols - 2
	b.Finish.Y = igloY
	b.Set(cols-2, igloY-1, Water)
	b.Set(cols-2, igloY+1, Water)
	return b
}

// Set the tile in column x and row y to val.
func (b *Board) Set(x, y int, val Tile) {
	b.Tiles[y*b.Cols+x] = val
}

// Get the tile in column x and row y.
func (b *Board) Get(x, y int) Tile {
	return b.Tiles[y*b.Cols+x]
}

func (b *Board) String() string {
	var buffer bytes.Buffer

	for y := 0; y < b.Rows; y++ {
		for x := 0; x < b.Cols; x++ {
			buffer.WriteString(b.Get(x, y).String())
		}
		buffer.WriteString(fmt.Sprintln())
	}

	return buffer.String()
}

func (b *Board) WriteJSON(w io.Writer, startCol, startRow, cols, rows int) {
	sc, sr, cols, rows := sanitizeViewPort(b, startCol, startRow, cols, rows)
	fmt.Fprintf(w, "{\"x\":%v,\"y\":%v,\"rows\":%v,\"cols\":%v,\"tiles\":[", sc, sr, cols, rows)

	for y := startRow; y < sr+rows; y++ {
		for x := startCol; x < sc+cols; x++ {
			if !(x == startCol && y == startRow) {
				w.Write([]byte{','})
			}
			t := &jsonTile{x, y, b.Get(x, y).Name(), ""}
			bs, _ := json.Marshal(t)
			w.Write(bs)
		}
	}

	fmt.Fprintf(w, "]}")
}

func sanitizeViewPort(b *Board, startCol, startRow, cols, rows int) (int, int, int, int) {
	if startCol > b.Cols {
		startCol = b.Cols
	}
	if startCol < 0 {
		cols += startCol
		startCol = 0
	}
	if startRow > b.Rows {
		startRow = b.Rows
	}
	if startRow < 0 {
		rows += startRow
		startRow = 0
	}
	if startCol+cols > b.Cols {
		cols = b.Cols - startCol
	}
	if startRow+rows > b.Rows {
		rows = b.Rows - startRow
	}
	if cols < 0 {
		cols = 0
	}
	if rows < 0 {
		rows = 0
	}
	return startCol, startRow, cols, rows
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}