package buffer

import (
	"io"
	"log/slog"
	"reflect"
	"testing"

	"code.chimeric.al/dwrz/wen/internal/editor/buffer/line"
)

func newTestBuffer(lines ...string) *Buffer {
	var b = &Buffer{
		cursor: &Cursor{},
		lines:  make([]*line.Line, 0, len(lines)),
		log:    slog.New(slog.NewTextHandler(io.Discard, nil)),
		offset: &offset{},
	}
	for _, s := range lines {
		b.lines = append(b.lines, line.New(s))
	}
	if len(b.lines) == 0 {
		b.lines = append(b.lines, &line.Line{})
	}

	return b
}

func bufferLines(b *Buffer) []string {
	var out = make([]string, len(b.lines))
	for i, l := range b.lines {
		out[i] = l.String()
	}

	return out
}

type CursorMoveTest struct {
	lines  []string
	action func(b *Buffer)
	want   Cursor
}

func TestCursorMovement(t *testing.T) {
	var tests = []CursorMoveTest{
		{
			lines:  []string{"ab", "cd"},
			action: func(b *Buffer) { b.CursorRight() },
			want:   Cursor{line: 0, index: 1, glyph: 1},
		},
		{
			lines: []string{"a", "b"},
			action: func(b *Buffer) {
				b.CursorRight()
				b.CursorRight()
			},
			want: Cursor{line: 1, index: 0, glyph: 0},
		},
		{
			lines: []string{"ab", "cd"},
			action: func(b *Buffer) {
				b.CursorDown()
				b.CursorLeft()
			},
			want: Cursor{line: 0, index: 2, glyph: 2},
		},
		{
			lines: []string{"hello", "hi"},
			action: func(b *Buffer) {
				b.CursorEnd()
				b.CursorDown()
			},
			want: Cursor{line: 1, index: 2, glyph: 2},
		},
		{
			lines: []string{"abc", "世界"},
			action: func(b *Buffer) {
				b.CursorRight()
				b.CursorDown()
			},
			want: Cursor{line: 1, index: 0, glyph: 0},
		},
		{
			lines: []string{"abc", "世界"},
			action: func(b *Buffer) {
				b.CursorEnd()
				b.CursorDown()
			},
			want: Cursor{line: 1, index: 3, glyph: 2},
		},
	}

	for n, test := range tests {
		b := newTestBuffer(test.lines...)
		test.action(b)
		if got := b.Cursor(); got != test.want {
			t.Errorf(
				"#%d: expected cursor %+v, but got %+v",
				n, test.want, got,
			)
		}
	}
}

type EditTest struct {
	lines      []string
	action     func(b *Buffer)
	wantLines  []string
	wantCursor Cursor
}

func TestEdit(t *testing.T) {
	var tests = []EditTest{
		{
			lines: []string{""},
			action: func(b *Buffer) {
				b.Insert('a')
				b.Insert('世')
			},
			wantLines:  []string{"a世"},
			wantCursor: Cursor{line: 0, index: 4, glyph: 3},
		},
		{
			lines:      []string{"hello"},
			action:     func(b *Buffer) { b.Newline() },
			wantLines:  []string{"", "hello"},
			wantCursor: Cursor{line: 1, index: 0, glyph: 0},
		},
		{
			lines: []string{"abcd"},
			action: func(b *Buffer) {
				b.CursorRight()
				b.CursorRight()
				b.Newline()
			},
			wantLines:  []string{"ab", "cd"},
			wantCursor: Cursor{line: 1, index: 0, glyph: 0},
		},
		{
			lines: []string{"abcd"},
			action: func(b *Buffer) {
				b.CursorEnd()
				b.Newline()
			},
			wantLines:  []string{"abcd", ""},
			wantCursor: Cursor{line: 1, index: 0, glyph: 0},
		},
		{
			lines: []string{"ab", ""},
			action: func(b *Buffer) {
				b.CursorDown()
				b.Backspace()
			},
			wantLines:  []string{"ab"},
			wantCursor: Cursor{line: 0, index: 2, glyph: 2},
		},
		{
			lines: []string{"ab", "cd"},
			action: func(b *Buffer) {
				b.CursorDown()
				b.Backspace()
			},
			wantLines:  []string{"abcd"},
			wantCursor: Cursor{line: 0, index: 2, glyph: 2},
		},
	}

	for n, test := range tests {
		b := newTestBuffer(test.lines...)
		test.action(b)
		if got := bufferLines(b); !reflect.DeepEqual(got, test.wantLines) {
			t.Errorf(
				"#%d: expected lines %q, but got %q",
				n, test.wantLines, got,
			)
		}
		if got := b.Cursor(); got != test.wantCursor {
			t.Errorf(
				"#%d: expected cursor %+v, but got %+v",
				n, test.wantCursor, got,
			)
		}
	}
}