// Copyright ©2020 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package font_test

import (
	"errors"
	"testing"

	stdfnt "golang.org/x/image/font"
	"golang.org/x/image/font/sfnt"
	"golang.org/x/image/math/fixed"
	"gonum.org/v1/plot/font"
	"gonum.org/v1/plot/font/liberation"
)

func TestFontExtends(t *testing.T) {
	cache := font.NewCache(liberation.Collection())
	for _, tc := range []struct {
		font font.Font
		want map[font.Length]font.Extents
	}{
		// values obtained when gonum/plot used the package
		// github.com/freetype/truetype for handling fonts.
		{
			font: font.Font{Typeface: "Liberation", Variant: "Serif"},
			want: map[font.Length]font.Extents{
				10: {
					Ascent:  8.9111328125,
					Descent: 2.1630859375,
					Height:  11.4990234375,
				},
				12: {
					Ascent:  10.693359375,
					Descent: 2.595703125,
					Height:  13.798828125,
				},
				24: {
					Ascent:  21.38671875,
					Descent: 5.19140625,
					Height:  27.59765625,
				},
			},
		},
		{
			font: font.Font{Typeface: "Liberation", Variant: "Serif", Weight: stdfnt.WeightBold},
			want: map[font.Length]font.Extents{
				10: {
					Ascent:  8.9111328125,
					Descent: 2.1630859375,
					Height:  11.4990234375,
				},
				12: {
					Ascent:  10.693359375,
					Descent: 2.595703125,
					Height:  13.798828125,
				},
				24: {
					Ascent:  21.38671875,
					Descent: 5.19140625,
					Height:  27.59765625,
				},
			},
		},
		{
			font: font.Font{Typeface: "Liberation", Variant: "Serif", Style: stdfnt.StyleItalic},
			want: map[font.Length]font.Extents{
				10: {
					Ascent:  8.9111328125,
					Descent: 2.1630859375,
					Height:  11.4990234375,
				},
				12: {
					Ascent:  10.693359375,
					Descent: 2.595703125,
					Height:  13.798828125,
				},
				24: {
					Ascent:  21.38671875,
					Descent: 5.19140625,
					Height:  27.59765625,
				},
			},
		},
		{
			font: font.Font{Typeface: "Liberation", Variant: "Serif", Style: stdfnt.StyleItalic, Weight: stdfnt.WeightBold},
			want: map[font.Length]font.Extents{
				10: {
					Ascent:  8.9111328125,
					Descent: 2.1630859375,
					Height:  11.4990234375,
				},
				12: {
					Ascent:  10.693359375,
					Descent: 2.595703125,
					Height:  13.798828125,
				},
				24: {
					Ascent:  21.38671875,
					Descent: 5.19140625,
					Height:  27.59765625,
				},
			},
		},
	} {
		for _, size := range []font.Length{10, 12, 24} {
			fnt := cache.Lookup(tc.font, size)
			got := fnt.Extents()
			if got, want := got, tc.want[size]; got != want {
				t.Errorf(
					"invalid font extents for %q, size=%v:\ngot= %#v\nwant=%#v",
					tc.font.Name(), size, got, want,
				)
			}
		}
	}
}

func TestFontWidth(t *testing.T) {
	cache := font.NewCache(liberation.Collection())
	fnt := cache.Lookup(font.Font{Typeface: "Liberation", Variant: "Serif"}, 12)

	for _, tc := range []struct {
		txt  string
		want font.Length
	}{
		// values obtained when gonum/plot used the package
		// github.com/freetype/truetype for handling fonts.
		{" ", 3},
		{"i", 3.333984375},
		{"q", 6},
		{"A", 8.666015625},
		{"F", 6.673828125},
		{"T", 7.330078125},
		{"V", 8.666015625},
		{"Δ", 7.716796875},
		{"∇", 9.333984375},
		{"  ", 6},
		{"AA", 17.33203125},
		{"Aq", 14.666015625},
		{"Fi", 10.0078125},
		{"Ti", 10.2421875},
		{"AV", 15.78515625},
		{"A∇", 18},
		{"VA", 15.78515625},
		{"VΔ", 16.3828125},
		{"∇Δ", 17.05078125},
		{"   ", 9},
		{"T T", 17.2265625},
	} {
		t.Run(tc.txt, func(t *testing.T) {
			got := fnt.Width(tc.txt)
			if got, want := got, tc.want; got != want {
				t.Fatalf(
					"invalid width: got=%v, want=%v",
					got, want,
				)
			}
		})
	}
}

func TestFontKern(t *testing.T) {
	cache := font.NewCache(liberation.Collection())
	fnt := cache.Lookup(font.Font{Typeface: "Liberation", Variant: "Serif"}, 12)

	for _, tc := range []struct {
		txt  string
		want fixed.Int26_6
	}{
		// values obtained when gonum/plot used the package
		// github.com/freetype/truetype for handling fonts.
		{"AV", -264},
		{"A∇", 0}, // Liberation has no kerning information for greek symbols
		{"AΔ", 0},
		{"AA", 0},
		{"VA", -264},
		{"∇A", 0}, // Liberation has no kerning information for greek symbols
		{"∇Δ", 0}, // Liberation has no kerning information for greek symbols
	} {
		t.Run(tc.txt, func(t *testing.T) {
			var (
				t0 = rune(tc.txt[0])
				t1 = rune(tc.txt[1])

				buf  sfnt.Buffer
				ppem = fixed.Int26_6(fnt.Face.UnitsPerEm())
			)

			i0, err := fnt.Face.GlyphIndex(&buf, t0)
			if err != nil {
				t.Fatalf("could not find glyph %q: %+v", t0, err)
			}
			i1, err := fnt.Face.GlyphIndex(&buf, t1)
			if err != nil {
				t.Fatalf("could not find glyph %q: %+v", t1, err)
			}
			kern, err := fnt.Face.Kern(&buf, i0, i1, ppem, stdfnt.HintingNone)
			switch {
			case err == nil:
				// ok
			case errors.Is(err, sfnt.ErrNotFound):
				kern = 0
			default:
				t.Fatalf("could not find kerning for %q/%q: %+v", t0, t1, err)
			}

			if got, want := kern, tc.want; got != want {
				t.Fatalf("invalid kerning: got=%v, want=%v", got, want)
			}
		})
	}
}

func TestFontName(t *testing.T) {
	for _, tc := range []struct {
		font *font.Font
		want string
	}{
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Sans",
				Style:    stdfnt.StyleNormal,
				Weight:   stdfnt.WeightNormal,
			},
			want: "LiberationSans-Regular",
		},
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Sans",
				Style:    stdfnt.StyleItalic,
				Weight:   stdfnt.WeightNormal,
			},
			want: "LiberationSans-Italic",
		},
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Sans",
				Style:    stdfnt.StyleNormal,
				Weight:   stdfnt.WeightBold,
			},
			want: "LiberationSans-Bold",
		},
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Sans",
				Style:    stdfnt.StyleItalic,
				Weight:   stdfnt.WeightBold,
			},
			want: "LiberationSans-BoldItalic",
		},
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Mono",
				Style:    stdfnt.StyleNormal,
				Weight:   stdfnt.WeightNormal,
			},
			want: "LiberationMono-Regular",
		},
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Mono",
				Style:    stdfnt.StyleItalic,
				Weight:   stdfnt.WeightNormal,
			},
			want: "LiberationMono-Italic",
		},
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Mono",
				Style:    stdfnt.StyleNormal,
				Weight:   stdfnt.WeightBold,
			},
			want: "LiberationMono-Bold",
		},
		{
			font: &font.Font{
				Typeface: "Liberation",
				Variant:  "Mono",
				Style:    stdfnt.StyleItalic,
				Weight:   stdfnt.WeightBold,
			},
			want: "LiberationMono-BoldItalic",
		},
	} {
		got := tc.font.Name()
		if got != tc.want {
			t.Errorf("invalid name: got=%q, want=%q", got, tc.want)
		}
	}
}