package preview

import (
	"strings"
	"testing"
)

var testColors = Colors{
	Background: "#100F0F", Text: "#CECDC3", Heading: "#D14D41", Code: "#879A39", Link: "#4385BE",
}

func renderPreview(t *testing.T, md string) string {
	t.Helper()
	m := New("dark")
	m.SetColors(testColors)
	m.SetSize(40, 20)
	if err := m.Render(md); err != nil {
		t.Fatal(err)
	}
	return m.View()
}

// H1 text must sit on the heading background, not the paper background.
func TestH1BackgroundBehindText(t *testing.T) {
	out := renderPreview(t, "# glint\n")
	if !strings.Contains(out, "48;2;209;77;65") {
		t.Fatalf("H1 missing heading background (209;77;65):\n%q", out)
	}
	// the word "glint" itself must carry the heading bg, not paper (16;15;15)
	if !strings.Contains(out, "48;2;209;77;65;1mglint") {
		t.Fatalf("H1 text not painted on heading background:\n%q", out)
	}
}

// Every ANSI reset must be followed by a re-assert of the paper background so
// unstyled regions (table borders, cell padding) never fall back to the
// terminal default — the table-background-between-themes bug.
func TestPaperBackgroundReassertedAfterResets(t *testing.T) {
	out := renderPreview(t, "| Key | Action |\n| --- | --- |\n| `Tab` | indent |\n")
	paper := "\x1b[38;2;206;205;195;48;2;16;15;15m" // text fg + paper bg
	resets := strings.Count(out, "\x1b[0m")
	reasserted := strings.Count(out, "\x1b[0m"+paper)
	if resets == 0 {
		t.Fatal("expected some resets in table output")
	}
	if resets != reasserted {
		t.Fatalf("bare resets remain: %d resets, %d re-asserted paper bg", resets, reasserted)
	}
}

// The bare "\x1b[m" reset form must also be followed by paper, else those
// regions fall back to the terminal background (cream-over-dark / dark-over-light
// bleed reported on real terminals).
func TestBareResetAlsoReassertsPaper(t *testing.T) {
	out := renderPreview(t, "# glint\n\n| Key | Action |\n| --- | --- |\n| `Tab` | indent |\n")
	paper := "\x1b[38;2;206;205;195;48;2;16;15;15m" // text fg + paper bg
	// Walk every ESC[m occurrence; each must be immediately followed by paper.
	for i := 0; ; {
		j := strings.Index(out[i:], "\x1b[m")
		if j < 0 {
			break
		}
		at := i + j
		if !strings.HasPrefix(out[at+len("\x1b[m"):], paper) {
			t.Fatalf("bare reset at %d not followed by paper bg: %q", at, out[at:min(at+24, len(out))])
		}
		i = at + len("\x1b[m")
	}
}

// H1 heading text must use the legible color for the heading background, not the
// prose text color (which can be illegible on the heading bar in light themes).
func TestH1TextUsesLegibleColor(t *testing.T) {
	out := renderPreview(t, "# glint\n")
	want := legibleText(testColors.Heading) // e.g. #FFFCF0 -> 255;252;240
	rgb := hexToRGB(want)
	if !strings.Contains(out, "38;2;"+rgb+";48;2;209;77;65;1mglint") {
		t.Fatalf("H1 text not using legible color %s (%s):\n%q", want, rgb, out)
	}
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}