// Copyright 2014 by Sascha L. Teichmann
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.

package main

import (
	"image"
	"image/color"
	"math"

	"bitbucket.org/s_l_teichmann/mtredisalize/common"
)

type Renderer struct {
	width    int
	height   int
	xOfs     int16
	zOfs     int16
	yBuffer  []int32
	cBuffer  []int32
	filled   int
	Rejected int
}

func NewRenderer(xOfs, zOfs int16, width, height int) (renderer *Renderer) {
	dim := width * height
	pixSize := dim * 16 * 16
	yBuffer := make([]int32, pixSize)
	cBuffer := make([]int32, pixSize)

	for i := 0; i < pixSize; i++ {
		yBuffer[i] = math.MinInt32
		cBuffer[i] = -1
	}

	renderer = &Renderer{
		width:   width,
		height:  height,
		xOfs:    xOfs,
		zOfs:    zOfs,
		yBuffer: yBuffer,
		cBuffer: cBuffer}
	return
}

func (r *Renderer) minY(ofs, w int) (minY int32, filled bool) {
	minY = int32(math.MaxInt32)
	for yEnd := ofs + w<<4; ofs < yEnd; {
		for xEnd := ofs + 16; ofs < xEnd; ofs++ {
			y := r.yBuffer[ofs]
			switch {
			case y == math.MaxInt32:
				return
			case y < minY:
				minY = y
			}
		}
		ofs += w - 16
	}
	filled = true
	return
}

func (r *Renderer) IsFilled() bool {
	return r.filled == r.width<<4*r.height<<4
}

func (r *Renderer) RenderBlock(block *common.Block, nameIndex map[string]int32) (err error) {

	bx := block.Coord.X - r.xOfs
	bz := block.Coord.Z - r.zOfs
	// We do not need to render the block if the whole 16x16 area
	// is already filled and the block is strictly below.
	w := r.width << 4
	ofs := int(bz)*w<<4 + int(bx)<<4
	blockY := int32(block.Coord.Y) << 4
	if minY, filled := r.minY(ofs, w); filled && blockY < minY {
		r.Rejected++
		return
	}

	// Decoding is pretty expensive so it that late.
	var db *DecodedBlock
	if db, err = NewDecodedBlock(block.Data, nameIndex); err != nil {
		return
	}

	for z := 0; z < 16; z++ {
		for x := 0; x < 16; x++ {
			if currentY := r.yBuffer[ofs]; currentY < blockY {
				for y := 15; y >= 0; y-- {
					if c, ok := db.Content(x, y, z); ok {
						if r.cBuffer[ofs] == -1 {
							r.filled++
						}
						r.cBuffer[ofs] = c
						r.yBuffer[ofs] = blockY + int32(y)
						break
					}
				}
			}
			ofs++
		}
		ofs += w - 16
	}

	return
}

func (r *Renderer) CreateImage(colors []color.RGBA, background color.RGBA) *image.RGBA {
	pw, ph := r.width<<4, r.height<<4
	image := image.NewRGBA(image.Rect(0, 0, pw, ph))
	ofs, numCols := 0, int32(len(colors))
	for z := ph - 1; z >= 0; z-- {
		for x := 0; x < pw; x++ {
			colIdx := r.cBuffer[ofs]
			if colIdx >= 0 && colIdx < numCols {
				image.Set(x, z, colors[colIdx])
			} else {
				image.Set(x, z, background)
			}
			ofs++
		}
	}
	return image
}

func safeColor(x int32) uint8 {
	if x < 0 {
		x = 0
	} else if x > 255 {
		x = 255
	}
	return uint8(x)
}

func (r *Renderer) CreateShadedImage(colors []color.RGBA, background color.RGBA) *image.RGBA {
	pw, ph := r.width<<4, r.height<<4
	image := image.NewRGBA(image.Rect(0, 0, pw, ph))
	ofs, numCols := 0, int32(len(colors))
	for z := ph - 1; z >= 0; z-- {
		for x := 0; x < pw; x++ {
			colIdx := r.cBuffer[ofs]
			if colIdx < 0 || colIdx >= numCols {
				image.Set(x, z, background)
			} else {
				var y, y1, y2 int32
				y = r.yBuffer[ofs]
				if x == 0 {
					y1 = y
				} else {
					y1 = r.yBuffer[ofs-1]
				}
				if z == 0 {
					y2 = y
				} else {
					y2 = r.yBuffer[ofs+pw]
				}
				d := ((y - y1) + (y - y2)) * 12
				if d > 36 {
					d = 36
				}
				col := colors[colIdx]
				image.Set(x, z, color.RGBA{
					R: safeColor(int32(col.R) + d),
					G: safeColor(int32(col.G) + d),
					B: safeColor(int32(col.B) + d),
					A: 0xff})
			}
			ofs++
		}
	}
	return image
}