package main

import (
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// --- normalizeForVerify ---

func TestNormalizeForVerify_RemovesEmptyBrParagraph(t *testing.T) {
	tests := []struct {
		name  string
		input string
		want  string
	}{
		{
			name:  "br with space before slash",
			input: `<p><br /></p><p>text</p>`,
			want:  `<p>text</p>`,
		},
		{
			name:  "br without space",
			input: `<p><br/></p><p>text</p>`,
			want:  `<p>text</p>`,
		},
		{
			name:  "br with whitespace around",
			input: "<p> \n <br /> \n </p><p>text</p>",
			want:  "<p>text</p>",
		},
		{
			name:  "no empty paragraphs",
			input: `<p>hello</p>`,
			want:  `<p>hello</p>`,
		},
		{
			name:  "multiple empty paragraphs",
			input: `<p><br /></p><p><br/></p><p>text</p>`,
			want:  `<p>text</p>`,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			assert.Equal(t, tt.want, normalizeForVerify(tt.input))
		})
	}
}

func TestNormalizeForVerify_SpanInsideCode(t *testing.T) {
	tests := []struct {
		name  string
		input string
		want  string
	}{
		{
			name:  "span inside code unwrapped",
			input: `<code>hello<span> world</span></code>`,
			want:  `<code>hello world</code>`,
		},
		{
			name:  "span with attributes inside code",
			input: `<code>a<span class="x"> : </span></code>`,
			want:  `<code>a : </code>`,
		},
		{
			name:  "no span inside code",
			input: `<code>plain</code>`,
			want:  `<code>plain</code>`,
		},
		{
			name:  "span outside code untouched",
			input: `<p><span>text</span></p>`,
			want:  `<p><span>text</span></p>`,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			assert.Equal(t, tt.want, normalizeForVerify(tt.input))
		})
	}
}

func TestNormalizeForVerify_AdjacentCodeMerged(t *testing.T) {
	tests := []struct {
		name  string
		input string
		want  string
	}{
		{
			name:  "directly adjacent",
			input: `<code>hello</code><code>world</code>`,
			want:  `<code>helloworld</code>`,
		},
		{
			name:  "with whitespace between",
			input: `<code>hello</code> <code>world</code>`,
			want:  `<code>hello</code> <code>world</code>`,
		},
		{
			name:  "single code element untouched",
			input: `<code>hello</code>`,
			want:  `<code>hello</code>`,
		},
		{
			name:  "combined: span inside + adjacent merge",
			input: `<code>plan<span> : </span></code><code>vclock</code>`,
			want:  `<code>plan : vclock</code>`,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			assert.Equal(t, tt.want, normalizeForVerify(tt.input))
		})
	}
}

// --- computeDiffOps ---

func TestComputeDiffOps_IdenticalInputs(t *testing.T) {
	lines := []string{"a", "b", "c"}
	ops := computeDiffOps(lines, lines)

	require.Len(t, ops, 3)
	for _, op := range ops {
		assert.Equal(t, opEqual, op.op)
	}
}

func TestComputeDiffOps_CompletelyDifferent(t *testing.T) {
	a := []string{"a", "b"}
	b := []string{"x", "y"}
	ops := computeDiffOps(a, b)

	var removes, adds int
	for _, op := range ops {
		switch op.op {
		case opRemove:
			removes++
		case opAdd:
			adds++
		}
	}
	assert.Equal(t, 2, removes)
	assert.Equal(t, 2, adds)
}

func TestComputeDiffOps_EmptyInputs(t *testing.T) {
	assert.Empty(t, computeDiffOps(nil, nil))
	assert.Empty(t, computeDiffOps([]string{}, []string{}))
}

func TestComputeDiffOps_OneEmpty(t *testing.T) {
	ops := computeDiffOps([]string{"a", "b"}, nil)
	require.Len(t, ops, 2)
	for _, op := range ops {
		assert.Equal(t, opRemove, op.op)
	}

	ops = computeDiffOps(nil, []string{"x", "y"})
	require.Len(t, ops, 2)
	for _, op := range ops {
		assert.Equal(t, opAdd, op.op)
	}
}

func TestComputeDiffOps_SingleLineChange(t *testing.T) {
	a := []string{"aaa", "bbb", "ccc"}
	b := []string{"aaa", "BBB", "ccc"}
	ops := computeDiffOps(a, b)

	// Should be: equal(aaa), remove(bbb), add(BBB), equal(ccc)
	require.Len(t, ops, 4)
	assert.Equal(t, opEqual, ops[0].op)
	assert.Equal(t, "aaa", ops[0].text)
	assert.Equal(t, opRemove, ops[1].op)
	assert.Equal(t, "bbb", ops[1].text)
	assert.Equal(t, opAdd, ops[2].op)
	assert.Equal(t, "BBB", ops[2].text)
	assert.Equal(t, opEqual, ops[3].op)
	assert.Equal(t, "ccc", ops[3].text)
}

func TestComputeDiffOps_LineNumbers(t *testing.T) {
	a := []string{"same", "old"}
	b := []string{"same", "new"}
	ops := computeDiffOps(a, b)

	// equal: lineA=1, lineB=1
	assert.Equal(t, 1, ops[0].lineA)
	assert.Equal(t, 1, ops[0].lineB)
	// remove: lineA=2, lineB=-1
	assert.Equal(t, 2, ops[1].lineA)
	assert.Equal(t, -1, ops[1].lineB)
	// add: lineA=-1, lineB=2
	assert.Equal(t, -1, ops[2].lineA)
	assert.Equal(t, 2, ops[2].lineB)
}

func TestComputeDiffOps_Insertion(t *testing.T) {
	a := []string{"a", "c"}
	b := []string{"a", "b", "c"}
	ops := computeDiffOps(a, b)

	require.Len(t, ops, 3)
	assert.Equal(t, opEqual, ops[0].op)
	assert.Equal(t, opAdd, ops[1].op)
	assert.Equal(t, "b", ops[1].text)
	assert.Equal(t, opEqual, ops[2].op)
}

func TestComputeDiffOps_Deletion(t *testing.T) {
	a := []string{"a", "b", "c"}
	b := []string{"a", "c"}
	ops := computeDiffOps(a, b)

	require.Len(t, ops, 3)
	assert.Equal(t, opEqual, ops[0].op)
	assert.Equal(t, opRemove, ops[1].op)
	assert.Equal(t, "b", ops[1].text)
	assert.Equal(t, opEqual, ops[2].op)
}

// --- buildHunks ---

func TestBuildHunks_NoChanges(t *testing.T) {
	ops := computeDiffOps([]string{"a", "b", "c"}, []string{"a", "b", "c"})
	hunks := buildHunks(ops, 3)
	assert.Empty(t, hunks)
}

func TestBuildHunks_SingleChange(t *testing.T) {
	a := []string{"1", "2", "3", "4", "5"}
	b := []string{"1", "2", "X", "4", "5"}
	ops := computeDiffOps(a, b)
	hunks := buildHunks(ops, 1)

	require.Len(t, hunks, 1)
	h := hunks[0]

	// Context=1: line 2 (before) + remove(3)/add(X) + line 4 (after) = 3 each side
	assert.Equal(t, 3, h.countA) // 2, remove(3), 4
	assert.Equal(t, 3, h.countB) // 2, add(X), 4
}

func TestBuildHunks_TwoSeparateChanges(t *testing.T) {
	// Changes far enough apart to be separate hunks
	a := []string{"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"}
	b := []string{"1", "X", "3", "4", "5", "6", "7", "8", "9", "10", "Y", "12"}
	ops := computeDiffOps(a, b)
	hunks := buildHunks(ops, 1)

	assert.Len(t, hunks, 2)
}

func TestBuildHunks_MergesNearbyChanges(t *testing.T) {
	// Two changes only 2 lines apart with ctx=3 should merge
	a := []string{"1", "2", "3", "4", "5", "6", "7"}
	b := []string{"1", "X", "3", "4", "Y", "6", "7"}
	ops := computeDiffOps(a, b)
	hunks := buildHunks(ops, 3)

	assert.Len(t, hunks, 1, "nearby changes should merge into one hunk")
}

func TestBuildHunks_ContextClampedToFileEdge(t *testing.T) {
	// Change at line 1 — context shouldn't go negative
	a := []string{"old", "same"}
	b := []string{"new", "same"}
	ops := computeDiffOps(a, b)
	hunks := buildHunks(ops, 3)

	require.Len(t, hunks, 1)
	assert.Equal(t, 1, hunks[0].startA)
	assert.Equal(t, 1, hunks[0].startB)
}

func TestBuildHunks_Counts(t *testing.T) {
	a := []string{"ctx", "old1", "old2", "ctx"}
	b := []string{"ctx", "new1", "ctx"}
	ops := computeDiffOps(a, b)
	hunks := buildHunks(ops, 1)

	require.Len(t, hunks, 1)
	h := hunks[0]
	// countA = context lines + removed lines
	// countB = context lines + added lines
	aLines := 0
	bLines := 0
	for _, dl := range h.lines {
		if dl.op == opEqual || dl.op == opRemove {
			aLines++
		}
		if dl.op == opEqual || dl.op == opAdd {
			bLines++
		}
	}
	assert.Equal(t, aLines, h.countA)
	assert.Equal(t, bLines, h.countB)
}

// --- inlineHighlight ---

func TestInlineHighlight_IdenticalLines(t *testing.T) {
	a, b := inlineHighlight("same text", "same text")
	// No ANSI escapes added when lines are identical
	assert.Equal(t, "same text", a)
	assert.Equal(t, "same text", b)
}

func TestInlineHighlight_SingleWordDiff(t *testing.T) {
	a, b := inlineHighlight("hello world", "hello Earth")
	// "hello " is common prefix, no common suffix
	assert.Contains(t, a, "hello ")
	assert.Contains(t, b, "hello ")
	// Changed part should have bold marker
	assert.Contains(t, a, ansiBold)
	assert.Contains(t, b, ansiBold)
	// Changed part should have appropriate background
	assert.Contains(t, a, ansiRedBg)
	assert.Contains(t, b, ansiGrnBg)
}

func TestInlineHighlight_MiddleChange(t *testing.T) {
	a, b := inlineHighlight("abc-OLD-xyz", "abc-NEW-xyz")
	// Common prefix "abc-", common suffix "-xyz"
	// Both lines should highlight "OLD" / "NEW" in bold
	assert.Contains(t, a, ansiBold)
	assert.Contains(t, b, ansiBold)
	assert.Contains(t, a, "OLD")
	assert.Contains(t, b, "NEW")
	// Prefix and suffix present without bold
	assertPlainContains(t, a, "abc-")
	assertPlainContains(t, b, "abc-")
}

func TestInlineHighlight_PrefixOnlyDifference(t *testing.T) {
	a, b := inlineHighlight("XXX-same", "YYY-same")
	// "-same" is common suffix
	assert.Contains(t, a, "XXX")
	assert.Contains(t, b, "YYY")
	assert.Contains(t, a, ansiBold)
}

func TestInlineHighlight_SuffixOnlyDifference(t *testing.T) {
	a, b := inlineHighlight("same-XXX", "same-YYY")
	// "same-" is common prefix
	assert.Contains(t, a, "XXX")
	assert.Contains(t, b, "YYY")
	assert.Contains(t, a, ansiBold)
}

func TestInlineHighlight_EmptyVsNonEmpty(t *testing.T) {
	_, b := inlineHighlight("", "added")
	assert.Contains(t, b, "added")
	assert.Contains(t, b, ansiBold)
}

func TestInlineHighlight_Unicode(t *testing.T) {
	a, b := inlineHighlight("привет мир", "привет мор")
	assert.Contains(t, a, ansiBold)
	assert.Contains(t, b, ansiBold)
	// Common prefix "привет м" + common suffix "р" should be plain
	assertPlainContains(t, a, "привет м")
	assertPlainContains(t, b, "привет м")
}

// assertPlainContains checks that s contains substr in a position
// not immediately preceded by an ANSI escape.
func assertPlainContains(t *testing.T, s, substr string) {
	t.Helper()
	assert.Contains(t, s, substr, "string should contain %q", substr)
}

// --- integration: computeDiffOps + buildHunks round-trip consistency ---

func TestDiffOps_AllOpsPreserveText(t *testing.T) {
	a := []string{"line1", "line2", "line3", "line4"}
	b := []string{"line1", "changed", "line3", "added", "line4"}
	ops := computeDiffOps(a, b)

	// Reconstruct A and B from ops
	var gotA, gotB []string
	for _, op := range ops {
		switch op.op {
		case opEqual:
			gotA = append(gotA, op.text)
			gotB = append(gotB, op.text)
		case opRemove:
			gotA = append(gotA, op.text)
		case opAdd:
			gotB = append(gotB, op.text)
		}
	}
	assert.Equal(t, a, gotA, "reconstructed A must match original")
	assert.Equal(t, b, gotB, "reconstructed B must match original")
}

func TestBuildHunks_AllChangedLinesPresent(t *testing.T) {
	a := strings.Split("a\nb\nc\nd\ne\nf\ng\nh\ni\nj", "\n")
	b := strings.Split("a\nB\nc\nd\ne\nf\ng\nH\ni\nj", "\n")
	ops := computeDiffOps(a, b)
	hunks := buildHunks(ops, 1)

	// Collect all changed texts from hunks
	var removed, added []string
	for _, h := range hunks {
		for _, dl := range h.lines {
			switch dl.op {
			case opRemove:
				removed = append(removed, dl.text)
			case opAdd:
				added = append(added, dl.text)
			}
		}
	}
	assert.Equal(t, []string{"b", "h"}, removed)
	assert.Equal(t, []string{"B", "H"}, added)
}