// 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 common

import (
	"fmt"
	"image/color"
	"log"
	"os"
	"path/filepath"
	"strconv"
)

const (
	tileWidth      = 18
	tileHeight     = 18
	yOrderCapacity = 512
)

// To scan the whole height in terms of the y coordinate
// the database is queried in height units defined in the tileDepths table.
var tileDepths = [...][2]int16{
	{1024, 1934},
	{256, 1023},
	{128, 255},
	{64, 127},
	{32, 63},
	{16, 31},
	{8, 15},
	{4, 7},
	{2, 3},
	{0, 1},
	{-1, 0},
	{-4, -2},
	{-8, -5},
	{-16, -9},
	{-32, -17},
	{-64, -33},
	{-128, -65},
	{-256, -129},
	{-1024, -257},
	{-1934, -1025}}

type BaseTileCreator struct {
	client   *RedisClient
	colors   *Colors
	renderer *Renderer
	yOrder   *YOrder
	baseDir  string
	update   bool
}

func NewBaseTileCreator(
	client *RedisClient,
	colors *Colors,
	baseDir string,
	update bool) *BaseTileCreator {
	renderer := NewRenderer(tileWidth, tileHeight)
	return &BaseTileCreator{
		client:   client,
		colors:   colors,
		renderer: renderer,
		yOrder:   NewYOrder(renderer, yOrderCapacity),
		baseDir:  baseDir,
		update:   update}
}

func (btc *BaseTileCreator) Close() error {
	return btc.client.Close()
}

func (btc *BaseTileCreator) CreateTile(x, z int16, i, j int) error {
	btc.renderer.Reset()
	btc.renderer.SetPos(x, z)
	btc.yOrder.Reset()

	drawBlock := func(block *Block) {
		if err := btc.yOrder.RenderBlock(block, btc.colors.NameIndex); err != nil {
			log.Printf("WARN: rendering block failed: %s", err)
		}
	}

	var c1, c2 Coord

	nareas := make([]Area, 0, tileWidth*tileHeight/2)
	oareas := make([]Area, 1, tileWidth*tileHeight/2)

	oareas[0] = Area{
		X1: 0, Z1: 0,
		X2: int16(tileWidth) - 1, Z2: int16(tileHeight) - 1}

	for _, yRange := range tileDepths {
		c1.Y = yRange[0]
		c2.Y = yRange[1]

		nareas = btc.renderer.UncoveredAreas(nareas, oareas)

		if len(nareas) == 0 {
			break
		}

		for _, area := range nareas {
			c1.X = area.X1 + x
			c1.Z = area.Z1 + z
			c2.X = area.X2 + x
			c2.Z = area.Z2 + z
			query := Cuboid{P1: c1, P2: c2}
			if err := btc.client.QueryCuboid(query, drawBlock); err != nil {
				return err
			}
			if err := btc.yOrder.Drain(btc.colors.NameIndex); err != nil {
				log.Printf("WARN: rendering block failed: %s", err)
			}
		}
		oareas, nareas = nareas, oareas[0:0]
	}

	image := btc.renderer.CreateShadedImage(
		16, 16, (tileWidth-2)*16, (tileHeight-2)*16,
		btc.colors.Colors, color.RGBA{R: 0xff, G: 0xff, B: 0xff, A: 0xff})

	path := filepath.Join(btc.baseDir, strconv.Itoa(i), fmt.Sprintf("%d.png", j))

	log.Printf("Writing (%d, %d) to file %s", x, z, path)

	if !btc.update {
		return SaveAsPNG(path, image)
	}

	// Try to make creation of update "atomic" by first writing to tmp file
	// and rename the tmp file to the original one afterwards.
	pathTmp := path + "tmp"
	pathTmpPre := pathTmp
	tc := 0
	for _, err := os.Stat(pathTmp); err == nil; _, err = os.Stat(pathTmp) {
		pathTmp = fmt.Sprintf("%s%d", pathTmpPre, tc)
		tc++
	}
	if err := SaveAsPNG(pathTmp, image); err != nil {
		return err
	}
	return os.Rename(pathTmp, path)
}