package ui

import (
	"image/color"

	"gioui.org/f32"
	"gioui.org/layout"
	"gioui.org/op"
	"gioui.org/op/clip"
	"gioui.org/op/paint"
	"gioui.org/text"
	"gioui.org/unit"
	"golang.org/x/image/math/fixed"
)

// ShapedText holds the result from ShapeText: width for positioning,
// plus the path data ready to draw. Must be drawn before the next ShapeText call.
type ShapedText struct {
	Width    int           // total width in pixels
	PathSpec clip.PathSpec // glyph path data
	Bitmaps  op.CallOp     // bitmap glyphs (may be empty)
	FirstX   fixed.Int26_6 // first glyph X offset
	FirstY   int32         // first glyph Y offset
}

// ShapeText layouts text and returns width + path data for drawing.
// The returned ShapedText must be drawn before the next ShapeText call.
func (r *Renderer) ShapeText(gtx layout.Context, str string, size unit.Sp) ShapedText {
	r.shp.LayoutString(text.Parameters{
		PxPerEm:  fixed.I(gtx.Sp(size)),
		MinWidth: 0,
		MaxWidth: 1000,
		MaxLines: 1,
	}, str)

	// Collect glyphs and measure width
	var glyphs []text.Glyph
	var cumWidth fixed.Int26_6
	var firstX fixed.Int26_6
	var firstY int32
	for {
		g, ok := r.shp.NextGlyph()
		if !ok {
			break
		}
		if len(glyphs) == 0 {
			firstX = g.X
			firstY = g.Y
		}
		cumWidth += g.Advance
		glyphs = append(glyphs, g)
	}

	// capture path spec
	var spec clip.PathSpec
	var bitmaps op.CallOp

	spec = r.shp.Shape(glyphs)
	bitmaps = r.shp.Bitmaps(glyphs)

	return ShapedText{
		Width:    int(cumWidth >> 6),
		PathSpec: spec,
		Bitmaps:  bitmaps,
		FirstX:   firstX,
		FirstY:   firstY,
	}
}

// DrawShapedText draws a ShapedText at the given position.
func (r *Renderer) DrawShapedText(gtx layout.Context, st ShapedText, x, y Dp, col color.NRGBA) {
	xPx := r.toPx(x)
	yPx := r.toPx(y)

	m := op.Record(gtx.Ops)

	offX := float32(xPx) + float32(st.FirstX)/64.0
	offY := float32(yPx) + float32(st.FirstY)
	t := op.Affine(f32.Affine2D{}.Offset(f32.Pt(offX, offY))).Push(gtx.Ops)

	outline := clip.Outline{Path: st.PathSpec}.Op().Push(gtx.Ops)
	paint.ColorOp{Color: col}.Add(gtx.Ops)
	paint.PaintOp{}.Add(gtx.Ops)
	outline.Pop()

	if st.Bitmaps != (op.CallOp{}) {
		st.Bitmaps.Add(gtx.Ops)
	}

	t.Pop()
	call := m.Stop()
	call.Add(gtx.Ops)
}