package text

import (
	"image/color"
	"math"
	"unicode"
	"unicode/utf8"

	"github.com/faiface/pixel"
	"golang.org/x/image/font"
)

var ASCII []rune

func init() {
	ASCII = make([]rune, unicode.MaxASCII-32)
	for i := range ASCII {
		ASCII[i] = rune(32 + i)
	}
}

func RangeTable(table *unicode.RangeTable) []rune {
	var runes []rune
	for _, rng := range table.R16 {
		for r := rng.Lo; r <= rng.Hi; r += rng.Stride {
			runes = append(runes, rune(r))
		}
	}
	for _, rng := range table.R32 {
		for r := rng.Lo; r <= rng.Hi; r += rng.Stride {
			runes = append(runes, rune(r))
		}
	}
	return runes
}

type Text struct {
	Orig pixel.Vec
	Dot  pixel.Vec

	atlas *Atlas

	lineHeight float64
	tabWidth   float64

	prevR  rune
	bounds pixel.Rect
	glyph  pixel.TrianglesData
	tris   pixel.TrianglesData

	mat    pixel.Matrix
	col    pixel.RGBA
	trans  pixel.TrianglesData
	transD pixel.Drawer
	dirty  bool
}

func New(face font.Face, runeSets ...[]rune) *Text {
	runes := []rune{unicode.ReplacementChar}
	for _, set := range runeSets {
		runes = append(runes, set...)
	}

	atlas := NewAtlas(face, runes)

	txt := &Text{
		atlas:      atlas,
		lineHeight: atlas.LineHeight(),
		tabWidth:   atlas.Glyph(' ').Advance * 4,
		mat:        pixel.IM,
		col:        pixel.Alpha(1),
	}

	txt.glyph.SetLen(6)
	for i := range txt.glyph {
		txt.glyph[i].Color = pixel.Alpha(1)
		txt.glyph[i].Intensity = 1
	}

	txt.transD.Picture = txt.atlas.pic
	txt.transD.Triangles = &txt.trans

	txt.Clear()

	return txt
}

func (txt *Text) Atlas() *Atlas {
	return txt.atlas
}

func (txt *Text) SetMatrix(m pixel.Matrix) {
	if txt.mat != m {
		txt.mat = m
		txt.dirty = true
	}
}

func (txt *Text) SetColorMask(c color.Color) {
	rgba := pixel.ToRGBA(c)
	if txt.col != rgba {
		txt.col = rgba
		txt.dirty = true
	}
}

func (txt *Text) Bounds() pixel.Rect {
	return txt.bounds
}

func (txt *Text) Color(c color.Color) {
	rgba := pixel.ToRGBA(c)
	for i := range txt.glyph {
		txt.glyph[i].Color = rgba
	}
}

func (txt *Text) LineHeight(scale float64) {
	txt.lineHeight = scale
}

func (txt *Text) TabWidth(width float64) {
	txt.tabWidth = width
}

func (txt *Text) Clear() {
	txt.prevR = -1
	txt.bounds = pixel.Rect{}
	txt.tris.SetLen(0)
	txt.dirty = true
}

func (txt *Text) Write(p []byte) (n int, err error) {
	n, err = len(p), nil // always returns this

	if len(p) == 0 {
		return
	}

	for len(p) > 0 {
		r, size := utf8.DecodeRune(p)
		p = p[size:]
		txt.WriteRune(r)
	}

	return
}

func (txt *Text) WriteString(s string) (n int, err error) {
	if len(s) == 0 {
		return
	}

	for _, r := range s {
		txt.WriteRune(r)
	}

	return len(s), nil
}

func (txt *Text) WriteByte(c byte) error {
	//FIXME: this is not correct, what if I want to write a 4-byte rune byte by byte?
	_, err := txt.WriteRune(rune(c))
	return err
}

func (txt *Text) WriteRune(r rune) (n int, err error) {
	n, err = utf8.RuneLen(r), nil // always returns this

	switch r {
	case '\n':
		txt.Dot -= pixel.Y(txt.lineHeight)
		txt.Dot = txt.Dot.WithX(txt.Orig.X())
		return
	case '\r':
		txt.Dot = txt.Dot.WithX(txt.Orig.X())
		return
	case '\t':
		rem := math.Mod(txt.Dot.X()-txt.Orig.X(), txt.tabWidth)
		rem = math.Mod(rem, rem+txt.tabWidth)
		if rem == 0 {
			rem = txt.tabWidth
		}
		txt.Dot += pixel.X(rem)
		return
	}

	if !txt.atlas.Contains(r) {
		r = unicode.ReplacementChar
	}
	if !txt.atlas.Contains(unicode.ReplacementChar) {
		return
	}

	glyph := txt.atlas.Glyph(r)

	if txt.prevR >= 0 {
		txt.Dot += pixel.X(txt.atlas.Kern(txt.prevR, r))
	}

	glyphBounds := glyph.Frame.Moved(txt.Dot - glyph.Orig)
	if glyphBounds.W()*glyphBounds.H() != 0 {
		glyphBounds = pixel.R(
			glyphBounds.Min.X(),
			txt.Dot.Y()-txt.Atlas().Descent(),
			glyphBounds.Max.X(),
			txt.Dot.Y()+txt.Atlas().Ascent(),
		)
		if txt.bounds.W()*txt.bounds.H() == 0 {
			txt.bounds = glyphBounds
		} else {
			txt.bounds = txt.bounds.Union(glyphBounds)
		}
	}

	a := pixel.V(glyph.Frame.Min.X(), glyph.Frame.Min.Y())
	b := pixel.V(glyph.Frame.Max.X(), glyph.Frame.Min.Y())
	c := pixel.V(glyph.Frame.Max.X(), glyph.Frame.Max.Y())
	d := pixel.V(glyph.Frame.Min.X(), glyph.Frame.Max.Y())

	for i, v := range []pixel.Vec{a, b, c, a, c, d} {
		txt.glyph[i].Position = v - glyph.Orig + txt.Dot
		txt.glyph[i].Picture = v
	}

	txt.tris = append(txt.tris, txt.glyph...)

	txt.Dot += pixel.X(glyph.Advance)
	txt.prevR = r

	txt.dirty = true

	return
}

func (txt *Text) Draw(t pixel.Target) {
	if txt.dirty {
		txt.trans.SetLen(txt.tris.Len())
		txt.trans.Update(&txt.tris)
		for i := range txt.trans {
			txt.trans[i].Position = txt.mat.Project(txt.trans[i].Position)
			txt.trans[i].Color = txt.trans[i].Color.Mul(txt.col)
		}
		txt.transD.Dirty()
		txt.dirty = false
	}
	txt.transD.Draw(t)
}