package generator

import (
	"strings"
	"testing"

	"mxl-pattern-generator/assets"

	"golang.org/x/image/font"
)

func testFace(t *testing.T, size float64) font.Face {
	t.Helper()
	face, err := NewFace(assets.JetBrainsMono, size)
	if err != nil {
		t.Fatalf("LoadFace: %v", err)
	}
	t.Cleanup(func() { face.Close() })
	return face
}

func TestNewTextOverlay(t *testing.T) {
	const frameW, frameH = 1920, 1080

	o, err := NewTextOverlay("AB", frameW, frameH, 0, 0, "", testFace(t, 48))
	if err != nil {
		t.Fatalf("NewTextOverlay: %v", err)
	}
	if o.w%6 != 0 {
		t.Fatalf("w=%d not a multiple of 6", o.w)
	}
	if o.x%6 != 0 {
		t.Fatalf("x=%d not a multiple of 6", o.x)
	}
	if o.x != 0 || o.y != 0 {
		t.Fatalf("position = (%d,%d), want (0,0)", o.x, o.y)
	}
	if o.blocks == nil || len(o.blocks) != o.h*(o.w/6)*16 {
		t.Fatalf("pre-packed tile has wrong size")
	}
	if o.cov[2*o.w+2] != 0 {
		t.Fatalf("padding pixel (2,2) covered: %d", o.cov[2*o.w+2])
	}
	nonzero, full := 0, 0
	for _, c := range o.cov {
		if c > 0 {
			nonzero++
		}
		if c == 255 {
			full++
		}
	}
	if nonzero < 100 {
		t.Fatalf("too few covered pixels: %d", nonzero)
	}
	if full == 0 {
		t.Fatalf("no fully covered (255) pixels")
	}

	// Text without descenders ("AB") must leave the bottom quarter empty;
	// text with a descender ("Ag") must have coverage there.
	for _, tc := range []struct {
		text    string
		wantAny bool
	}{
		{"AB", false},
		{"Ag", true},
	} {
		o, err := NewTextOverlay(tc.text, frameW, frameH, 0, 0, "", testFace(t, 48))
		if err != nil {
			t.Fatalf("NewTextOverlay(%q): %v", tc.text, err)
		}
		any := false
		for row := o.h * 3 / 4; row < o.h; row++ {
			for col := 0; col < o.w; col++ {
				if o.cov[row*o.w+col] > 0 {
					any = true
				}
			}
		}
		if any != tc.wantAny {
			t.Fatalf("%q: coverage in bottom quarter = %v, want %v", tc.text, any, tc.wantAny)
		}
	}
}

func TestNewTextOverlayPositioning(t *testing.T) {
	const frameW, frameH = 1920, 1080
	face := testFace(t, 48)

	t.Run("explicit", func(t *testing.T) {
		o, err := NewTextOverlay("AB", frameW, frameH, 120, 48, "", face)
		if err != nil {
			t.Fatalf("NewTextOverlay: %v", err)
		}
		if o.x != 120 || o.y != 48 {
			t.Fatalf("position = (%d,%d), want (120,48)", o.x, o.y)
		}
	})

	for _, tc := range []struct {
		name string
		pos  string
		want func(*TextOverlay) bool
	}{
		{name: "top center", pos: "tc", want: func(o *TextOverlay) bool {
			return o.x%6 == 0 && absInt((o.x+o.w/2)-frameW/2) <= 3 && o.y == 0
		}},
		{name: "center", pos: "cc", want: func(o *TextOverlay) bool {
			return o.x%6 == 0 && absInt((o.x+o.w/2)-frameW/2) <= 3 && o.y == (frameH-o.h)/2
		}},
		{name: "bottom right", pos: "br", want: func(o *TextOverlay) bool {
			return o.x+o.w == frameW && o.y+o.h == frameH
		}},
	} {
		t.Run(tc.name, func(t *testing.T) {
			o, err := NewTextOverlay("AB", frameW, frameH, 0, 0, tc.pos, face)
			if err != nil {
				t.Fatalf("NewTextOverlay: %v", err)
			}
			if !tc.want(o) {
				t.Fatalf("unexpected %s position: box=(%d,%d %dx%d)", tc.pos, o.x, o.y, o.w, o.h)
			}
		})
	}
}

func TestNewTextOverlayRejectsInvalidPosition(t *testing.T) {
	const frameW, frameH = 1920, 1080
	face := testFace(t, 48)

	tests := []struct {
		name       string
		x, y       int
		wantErrSub string
	}{
		{name: "unaligned x", x: 7, y: 0, wantErrSub: "divisible by 6"},
		{name: "negative x", x: -6, y: 0, wantErrSub: "must not be negative"},
		{name: "right overflow", x: 1902, y: 0, wantErrSub: "does not fit"},
		{name: "bottom overflow", x: 0, y: 1070, wantErrSub: "does not fit"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			_, err := NewTextOverlay("AB", frameW, frameH, tc.x, tc.y, "", face)
			if err == nil || !strings.Contains(err.Error(), tc.wantErrSub) {
				t.Fatalf("error = %v, want substring %q", err, tc.wantErrSub)
			}
		})
	}
}

func absInt(v int) int {
	if v < 0 {
		return -v
	}
	return v
}

func TestTextOverlayApplyV210(t *testing.T) {
	const frameW, frameH = 1920, 1080
	o, err := NewTextOverlay("MXL", frameW, frameH, 0, 0, "", testFace(t, 48))
	if err != nil {
		t.Fatalf("NewTextOverlay: %v", err)
	}

	frame := make([]byte, V210FrameSize(frameW, frameH))
	for i := range frame {
		frame[i] = 0x5A // marker: untouched regions must survive
	}
	if err := o.ApplyV210(frame); err != nil {
		t.Fatalf("ApplyV210: %v", err)
	}

	// Every box pixel: Y from coverage, neutral chroma at even columns.
	for row := 0; row < o.h; row++ {
		for col := 0; col < o.w; col++ {
			wantY := uint32(64 + (int(o.cov[row*o.w+col])*876+127)/255)
			yc, cb, cr := sampleV210(frame, frameW, o.x+col, o.y+row)
			if yc != wantY {
				t.Fatalf("box pixel (%d,%d): Y=%d, want %d", o.x+col, o.y+row, yc, wantY)
			}
			if (o.x+col)%2 == 0 && (cb != 512 || cr != 512) {
				t.Fatalf("box pixel (%d,%d): Cb=%d Cr=%d, want 512/512", o.x+col, o.y+row, cb, cr)
			}
		}
	}

	// Blocks just outside the box (right edge and below) must be untouched.
	for _, p := range [][2]int{
		{o.x + o.w, o.y},       // right of box, block-aligned
		{o.x, o.y + o.h},       // below box
		{o.x + o.w, o.y + o.h}, // corner
		{100, 1000},            // far away
	} {
		off := p[1]*V210LineSize(frameW) + p[0]/6*16
		for i := 0; i < 16; i++ {
			if frame[off+i] != 0x5A {
				t.Fatalf("block at (%d,%d) modified outside the box", p[0], p[1])
			}
		}
	}
}