package board

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

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 {
	b := &Board{
		Cols:  cols,
		Rows:  rows,
		Tiles: make([]Tile, rows*cols)}

	for y := 0; y < rows; y++ {
		for x := 0; x < cols; x++ {
			b.randomizeTile(x, y)
		}
	}

	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 (b *Board) randomizeTile(x, y int) {

	switch {
	case b.isIglo(x, y):
		b.Set(x, y, Iglo)
		b.Finish.X = x
		b.Finish.Y = y
	case b.isRock(x, y):
		b.Set(x, y, Rock)
	case b.isIce(x, y):
		b.Set(x, y, Ice)
	default:
		b.Set(x, y, Water)
	}

}

func (b *Board) isIglo(x, y int) bool {
	return x == (b.Cols-1) && y == (b.Rows-1)/2
}

func (b *Board) isRock(x, y int) bool {
	return rand.Intn(10) > 7
}

func (b *Board) isIce(x, y int) bool {
	leftLimit := (b.Cols - maxIceWidth) / 2
	rightLimit := b.Cols/2 + maxIceWidth/2
	return x > leftLimit && x < rightLimit && rand.Intn(maxIceWidth) >= abs((b.Cols/2)-x)
}

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