package caption

import (
	"image"
	"image/color"

	"github.com/golang/freetype/truetype"
	"golang.org/x/image/draw"
	"golang.org/x/image/font"
	"golang.org/x/image/math/fixed"
)

type Line struct {
	// collection of all text segments
	Data []Segment `json:"data"`
	// applies to all segments; avoid direct assignment and use SetFont instead
	Font []byte `json:"font"`
	// applies to all segments; avoid direct assignment and use SetFont instead
	Options *truetype.Options `json:"options"`

	// contains reference to parsed font, populated once per instance
	face font.Face
}

// SetFont clears line font cache and sets the new font.
func (l *Line) SetFont(v []byte, opts *truetype.Options) { l.face = nil; l.Font = v; l.Options = opts }

type Segment struct {
	Value string      `json:"value"`
	Color color.Color `json:"color"`
}

func (l *Line) Render(frame draw.Image, x, y int) error {
	if l.face == nil {
		if len(l.Font) == 0 {
			l.SetFont(defaultFont, l.Options)
		}
		if f, err := truetype.Parse(l.Font); err != nil {
			return err
		} else {
			l.face = truetype.NewFace(f, l.Options)
		}
	}

	drawer := &font.Drawer{Dst: frame, Face: l.face, Dot: fixed.Point26_6{X: fixed.I(x), Y: fixed.I(y)}}
	for _, seg := range l.Data {
		drawer.Src = image.NewUniform(seg.Color)
		drawer.DrawString(seg.Value)
	}

	return nil
}