// 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 (
	"encoding/json"
	"fmt"
	"image/color"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"sync"

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

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 yRanges table.
var yRanges = [][]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 tileUpdater struct {
	changes      map[xz]bool
	mapDir       string
	redisAddress string
	colors       *common.Colors
	workers      int
	cond         *sync.Cond
	mu           sync.Mutex
}

type xz struct {
	X int16
	Z int16
}

func (c xz) quantize() xz {
	return xz{X: (c.X - -1936) / 16, Z: (c.Z - -1936) / 16}
}

func newTileUpdater(mapDir, redisAddress string, colors *common.Colors, workers int) *tileUpdater {
	tu := tileUpdater{
		mapDir:       mapDir,
		redisAddress: redisAddress,
		changes:      map[xz]bool{},
		colors:       colors,
		workers:      workers}
	tu.cond = sync.NewCond(&tu.mu)
	return &tu
}

func (tu *tileUpdater) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
	var err error
	var newChanges []xz
	decoder := json.NewDecoder(r.Body)
	if err = decoder.Decode(&newChanges); err != nil {
		log.Printf("WARN: JSON document broken: %s", err)
		http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
		return
	}

	tu.cond.L.Lock()
	for _, c := range newChanges {
		tu.changes[c.quantize()] = true
	}
	tu.cond.L.Unlock()
	tu.cond.Signal()

	rw.WriteHeader(http.StatusOK)
}

func (tu *tileUpdater) doUpdates() (err error) {

	jobs := make(chan xz)

	baseDir := filepath.Join(tu.mapDir, "8")

	for i := 0; i < tu.workers; i++ {
		var client *common.RedisClient
		if client, err = common.NewRedisClient("tcp", tu.redisAddress); err != nil {
			return
		}
		btc := NewBaseTileCreator(client, tu.colors, baseDir, true)
		go btc.run(jobs)
	}

	go func() {
		for {
			var changes map[xz]bool
			tu.cond.L.Lock()
			for len(tu.changes) == 0 {
				tu.cond.Wait()
			}
			changes = tu.changes
			tu.changes = map[xz]bool{}
			tu.cond.L.Unlock()

			for c, _ := range changes {
				log.Printf("job: %+v", c)
				jobs <- c
			}
		}
	}()
	return
}

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

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

func (btc *BaseTileCreator) run(jobs chan xz) {
	for job := range jobs {
		x := job.X*16 + -1936 - 1
		z := job.Z*16 + -1936 - 1
		log.Printf("%d/%d %d/%d", x, z, job.X, job.Z)
		if err := btc.createTile(x, z, int(job.X), int(job.Z)); err != nil {
			log.Printf("WARN: create tile failed: %s", err)
		}
	}
}

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

	var c1, c2 common.Coord

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

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

	for _, yRange := range yRanges {
		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 := common.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 common.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 := common.SaveAsPNG(pathTmp, image); err != nil {
		return err
	}
	return os.Rename(pathTmp, path)
}