package data

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

var (
	// FIXME: My poor understanding of the .obj format prevents me from
	// successfully loading these files
	objBlacklist = []string{
		/* Lots of unexpected magic values, disable the check for now
		"15_rocks.obj", // Unexpected magic value: 19726564 (expected 21102801)
		"2_cath.obj",   // Unexpected magic value: 21364973 (expected 21102801)
		"2nd_flor.obj", // Unexpected magic value: 22151377 (expected 21102801)
		"3_cath.obj",   // Unexpected magic value: 21102809 (expected 21102801)
		"4_cath.obj",   // Unexpected magic value: 21496017 (expected 21102801)
		"BODIES.obj",   // Unexpected magic value: 21627103 (expected 21102801)
		"BRDG_TIL.OBJ", // Unexpected magic value: 17957074 (expected 21102801)
		"Cheveron.obj", // Unexpected magic value: 10879118 (expected 21102801)

		"Heavy_Plasma_Effect.obj",      // Unexpected magic value: 14811345 (expected 21102801)
		"Heavy_Plasma_Mask.obj",        // Unexpected magic value: 14811345 (expected 21102801)
		"Heavy_Plasma_Pain_Effect.obj", // Unexpected magic value: 14811345 (expected 21102801)
		"Heavy_Plasma_Pain_Mask.obj",   // Unexpected magic value: 14811345 (expected 21102801)

		"Ht_drt.obj", // Unexpected magic value: 22806737 (expected 21102801)
		"Ht_grs.obj", // Unexpected magic value: 22806737 (expected 21102801)

		"IVY02.OBJ", // Unexpected magic value: 18481399 (expected 21102801)
		"J_top2.obj", // Unexpected magic value: 22347993 (expected 21102801)

		"Lascannon_Effect.obj", // Unexpected magic value: 14811345 (expected 21102801)
		"Lascannon_Mask.obj",   // Unexpected magic value: 14811345 (expected 21102801)
		"Lascannon_Pain_Effect.obj", // Unexpected magic value: 14811345 (expected 21102801)
		"Lascannon_Pain_Mask.obj", // Unexpected magic value: 14811136 (expected 21102801)

		"Man_Shadow.obj", // Unexpected magic value: 22479091 (expected 21102801)

		"Melta_Effect.obj", // Unexpected magic value: 14745777 (expected 21102801)
		"Melta_Mask.obj", // Unexpected magic value: 14811345 (expected 21102801)
		"Melta_Pain_Effect.obj", // Unexpected magic value: 14745777 (expected 21102801)
		"Melta_Pain_Mask.obj", // Unexpected magic value: 14811345 (expected 21102801)

		"Multi_Melta_Effect.obj",
		"Multi_Melta_Mask.obj",
		"Multi_Melta_Pain_Effect.obj",
		"Multi_Melta_Pain_Mask.obj",

		"Plasma_Effect.obj",      // Unexpected magic value: 14811345 (expected 21102801)
		"Plasma_Mask.obj",        // Unexpected magic value: 14811345 (expected 21102801)
		"Plasma_Pain_Effect.obj", // Unexpected magic value: 14811345 (expected 21102801)
		"Plasma_Pain_Mask.obj",   // Unexpected magic value: 14811345 (expected 21102801)

		"TZEENTCH.OBJ", // Unexpected magic value: 18088209 (expected 21102801)

		"altar.obj", // Unexpected magic value: 18219222 (expected 21102801)
		*/

		"j_tree2.obj", // ObjectHeader is completely empty
		"inven.obj",   // Main header padding contains unknown values: [134744072 134744072 134744072]
	}
	objFrameMagic = uint32(0x014200D1)
)

func init() {
	sort.Strings(objBlacklist)
}

type FrameHeader struct {
	Magic     uint32
	Width     uint16 // FIXME: I'm not certain this is what these are. If they are, they may be the wrong way around
	Height    uint16
	Padding1  uint32 // I don't think this is used. Could be wrong.
	PixelSize uint32 // Size of PixelData, excluding this frame header
	Padding2  uint64 // I don't think this is used either. Could be wrong.
}

func (f FrameHeader) Check(expectedSize uint32) error {
	// There seem to be different frame types, keyed by the magic value?
	// if f.Magic != objFrameMagic {
	// 	return fmt.Errorf("Unexpected magic value: %d (expected %d)", f.Magic, objFrameMagic)
	// }

	if f.Padding1 != 0 || f.Padding2 != 0 {
		return fmt.Errorf("Frame header padding contains unknown values: %d %d", f.Padding1, f.Padding2)
	}

	// Remove 24 bytes from passed-in size to account for the header
	if f.PixelSize != expectedSize-24 {
		return fmt.Errorf("Advertised pixel size: %d differs from expected: %v", f.PixelSize, expectedSize-24)
	}

	return nil
}

type Frame struct {
	FrameHeader

	PixelData []byte
}

type frameInfoHeader struct {
	Offset uint32 // Offset of the frame relative to the frame data segment
	Size   uint32 // Size of the frame in bytes, including the header
}

func (f frameInfoHeader) Check() error {
	if f.Size < 24 {
		return fmt.Errorf("Unexpected frame size: %d (expected >= 24)", f.Size)
	}

	return nil
}

// ObjectHeader totals 32 bytes on disk
type ObjectHeader struct {
	NumFrames       uint32 // How many frames does this object have?
	MainHeaderSize  uint32 // Number of bytes taken by this header. Should always be `32`
	FrameInfoSize   uint32 // Number of bytes taken up by the next block. 8 * NumFrames
	FrameDataOffset uint32 // The starting point of the frame data
	FrameDataSize   uint32 // frame data should take up this many bytes

	Padding [3]uint32 // Unused, as far as I can see
}

func (h ObjectHeader) ExpectedFrameInfoSize() uint32 {
	return h.NumFrames * 8
}

func (h ObjectHeader) Check() error {
	if h.MainHeaderSize != 32 {
		return fmt.Errorf("Unexpected main header size: %d (expected 32)", h.MainHeaderSize)
	}

	if h.ExpectedFrameInfoSize() != h.FrameInfoSize {
		return fmt.Errorf("Unexpected frame info size: %d (expected %d)", h.FrameInfoSize, h.ExpectedFrameInfoSize())
	}

	if h.Padding[0] != 0 || h.Padding[1] != 0 || h.Padding[2] != 0 {
		return fmt.Errorf("Main header padding contains unknown values: %+v", h.Padding)
	}

	return nil
}

type Object struct {
	ObjectHeader

	Filename string
	Frames   []*Frame
}

func LoadObject(filename string) (*Object, error) {
	f, err := os.Open(filename)
	if err != nil {
		return nil, err
	}

	defer f.Close()

	out := &Object{Filename: filename}
	if err := binary.Read(f, binary.LittleEndian, &out.ObjectHeader); err != nil {
		return nil, err
	}

	if err := out.ObjectHeader.Check(); err != nil {
		return nil, err
	}

	// Now load all frames into memory

	framesInfo := make([]frameInfoHeader, out.NumFrames)
	if err := binary.Read(f, binary.LittleEndian, &framesInfo); err != nil {
		return nil, err
	}

	if _, err := f.Seek(int64(out.FrameDataOffset), io.SeekStart); err != nil {
		return nil, err
	}

	// FIXME: this might - *might* - load interstitial data we don't really
	// need, so wasting memory.
	data, err := ioutil.ReadAll(f)
	if err != nil {
		return nil, err
	}

	buf := bytes.NewReader(data)

	for _, frameInfo := range framesInfo {
		if err := frameInfo.Check(); err != nil {
			return nil, err
		}

		if _, err := buf.Seek(int64(frameInfo.Offset), io.SeekStart); err != nil {
			return nil, err
		}

		frame := &Frame{}

		if err := binary.Read(buf, binary.LittleEndian, &frame.FrameHeader); err != nil {
			return nil, err
		}

		if err := frame.Check(frameInfo.Size); err != nil {
			return nil, err
		}

		// It's safe to assume that a `bytes.Reader` will always satisfy the
		// requested read size.
		frame.PixelData = make([]byte, frame.PixelSize)
		if _, err := buf.Read(frame.PixelData); err != nil {
			return nil, err
		}

		out.Frames = append(out.Frames, frame)
	}

	return out, nil
}

func readObjFrame(f io.Reader, obj *Object) error {
	return nil
}

func LoadObjects(dir string) (map[string]*Object, error) {
	fis, err := ioutil.ReadDir(dir)
	if err != nil {
		return nil, err
	}

	out := make(map[string]*Object, len(fis))

	for _, fi := range fis {
		filename := filepath.Join(dir, fi.Name())
		basename := filepath.Base(filename)
		extname := filepath.Ext(filename)

		// Don't try to load non-.obj files
		if !strings.EqualFold(extname, ".obj") {
			continue
		}

		i := sort.SearchStrings(objBlacklist, basename)
		if i >= len(objBlacklist) || objBlacklist[i] == basename {
			continue
		}

		obj, err := LoadObject(filename)
		if err != nil {
			return nil, fmt.Errorf("%s: %v", filename, err)
		}

		out[basename] = obj
	}

	return out, nil
}