package editor

import (
	"strings"
	"testing"

	"codeberg.org/turbo-editors/turbo-core/buffer"
)

// viewOn returns a view on a buffer holding text, with the cursor placed.
func viewOn(t *testing.T, text string, line, col int) *View {
	t.Helper()

	buf := buffer.New()
	buf.SetText(text)
	v := NewView(buf, &Clipboard{})
	buf.SetCursor(buffer.Position{Line: line, Col: col})
	return v
}

func TestInsertSnippetPutsASingleLineAtTheCursor(t *testing.T) {
	v := viewOn(t, "abcd\n", 0, 2)

	v.InsertSnippet("XY")

	if got := v.Buffer().Text(); got != "abXYcd\n" {
		t.Errorf("the buffer holds %q", got)
	}
}

func TestInsertSnippetIndentsTheLinesAfterTheFirst(t *testing.T) {
	// The case that decides the whole feature: a multi-line snippet dropped
	// into indented code restarts at column zero without this.
	v := viewOn(t, "func f() {\n\t\n}\n", 1, 1)

	v.InsertSnippet("if err != nil {\n\treturn err\n}")

	want := "func f() {\n\tif err != nil {\n\t\treturn err\n\t}\n}\n"
	if got := v.Buffer().Text(); got != want {
		t.Errorf("the buffer holds\n%q\nwant\n%q", got, want)
	}
}

func TestInsertSnippetUsesSpacesWhenTheLineDoes(t *testing.T) {
	v := viewOn(t, "x = [\n    \n]\n", 1, 4)

	v.InsertSnippet("a,\nb,")

	want := "x = [\n    a,\n    b,\n]\n"
	if got := v.Buffer().Text(); got != want {
		t.Errorf("the buffer holds\n%q\nwant\n%q", got, want)
	}
}

func TestInsertSnippetAtColumnZeroAddsNoIndent(t *testing.T) {
	v := viewOn(t, "\n", 0, 0)

	v.InsertSnippet("a\nb\nc")

	if got := v.Buffer().Text(); got != "a\nb\nc\n" {
		t.Errorf("the buffer holds %q", got)
	}
}

func TestInsertSnippetLeavesBlankLinesBlank(t *testing.T) {
	// Trailing whitespace on an empty line is something every formatter then
	// removes, so putting it there is noise in the next diff.
	v := viewOn(t, "func f() {\n\t\n}\n", 1, 1)

	v.InsertSnippet("a\n\nb")

	want := "func f() {\n\ta\n\n\tb\n}\n"
	if got := v.Buffer().Text(); got != want {
		t.Errorf("the buffer holds\n%q\nwant\n%q", got, want)
	}
}

func TestInsertSnippetIsOneUndoStep(t *testing.T) {
	v := viewOn(t, "func f() {\n\t\n}\n", 1, 1)
	before := v.Buffer().Text()

	v.InsertSnippet("if err != nil {\n\treturn err\n}")
	v.Buffer().Undo()

	if got := v.Buffer().Text(); got != before {
		t.Errorf("one undo left\n%q\nwant\n%q", got, before)
	}
}

func TestInsertSnippetLeavesTheCursorAfterTheText(t *testing.T) {
	v := viewOn(t, "func f() {\n\t\n}\n", 1, 1)

	v.InsertSnippet("a\nb")

	cursor := v.Buffer().Cursor()
	if cursor.Line != 2 {
		t.Errorf("the cursor is on line %d, want the last line of the snippet", cursor.Line)
	}
	if got := v.Buffer().Line(cursor.Line); cursor.Col != len([]rune(got)) {
		t.Errorf("the cursor is at column %d of %q, want the end", cursor.Col, got)
	}
}

func TestInsertSnippetCountsAsAChange(t *testing.T) {
	v := viewOn(t, "x\n", 0, 0)
	before := v.Buffer().Revision()

	v.InsertSnippet("y")

	if v.Buffer().Revision() == before {
		t.Error("inserting a snippet did not move the revision, so nothing will re-colour")
	}
	if !v.Buffer().Modified() {
		t.Error("inserting a snippet left the buffer unmodified")
	}
}

func TestInsertingAnEmptySnippetChangesNothing(t *testing.T) {
	// The revision is what says nothing happened; Modified() cannot, because
	// putting the text into the buffer in the first place already set it.
	v := viewOn(t, "x\n", 0, 0)
	before := v.Buffer().Revision()

	v.InsertSnippet("")

	if got := v.Buffer().Text(); got != "x\n" {
		t.Errorf("the buffer holds %q", got)
	}
	if v.Buffer().Revision() != before {
		t.Error("an empty snippet moved the revision")
	}
}

func TestInsertSnippetHandlesAccentsInTheCurrentLine(t *testing.T) {
	// The indent is taken as a byte prefix of the line, so a line whose text
	// has accents must still give back only its whitespace.
	if got := leadingWhitespace("\t  évidemment"); got != "\t  " {
		t.Errorf("leadingWhitespace() = %q, want the tab and two spaces", got)
	}
}

func TestLeadingWhitespaceOfABlankLineIsTheWholeLine(t *testing.T) {
	if got := leadingWhitespace("\t\t"); got != "\t\t" {
		t.Errorf("leadingWhitespace() = %q", got)
	}
	if got := leadingWhitespace(""); got != "" {
		t.Errorf("leadingWhitespace() = %q", got)
	}
}

func TestIndentContinuationLinesLeavesASingleLineAlone(t *testing.T) {
	if got := indentContinuationLines("only", "\t"); got != "only" {
		t.Errorf("got %q, want the text unchanged", got)
	}
	if strings.Contains(indentContinuationLines("only", "\t"), "\t") {
		t.Error("a single-line snippet was indented")
	}
}