package editor

import (
	"testing"

	"pad/internal/ui"
)

// TestCursorPositioning_Basic verifies cursor positioning via GlyphLayout.
func TestCursorPositioning_Basic(t *testing.T) {
	TheState = NewState()
	TheState.Editor.Buffer = "hello\nworld"

	// Two lines: "hello\n" (bytes 0-5) and "world" (bytes 6-10)
	// Line 0 glyphs at Y=70, Line 1 glyphs at Y=140
	TheState.Editor.GlyphLayout = ui.GlyphLayout{
		ByteOffsets: []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10},
		X:           []ui.Dp{10, 20, 30, 40, 50, 10, 20, 30, 40, 50, 60},
		Y:           []ui.Dp{70, 70, 70, 70, 70, 70, 140, 140, 140, 140, 140},
		Advance:     []ui.Dp{10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
	}

	// Test tapping on first line near X=30 (glyph index 2, byteOffset 2)
	SetCursorFromPoint(25, 70)
	if TheState.Editor.CursorPosition < 0 || TheState.Editor.CursorPosition > len(TheState.Editor.Buffer) {
		t.Errorf("cursor position %d out of bounds after first tap", TheState.Editor.CursorPosition)
	}

	// Test tapping on second line
	SetCursorFromPoint(35, 140)
	if TheState.Editor.CursorPosition < 0 || TheState.Editor.CursorPosition > len(TheState.Editor.Buffer) {
		t.Errorf("cursor position %d out of bounds after second tap", TheState.Editor.CursorPosition)
	}
}

// TestCursorPositioning_EmptyDocument verifies cursor positioning handles empty documents.
func TestCursorPositioning_EmptyDocument(t *testing.T) {
	TheState = NewState()
	TheState.Editor.Buffer = ""
	TheState.Editor.GlyphLayout = ui.GlyphLayout{}

	// Should not panic on empty layout
	SetCursorFromPoint(50, 50)

	if TheState.Editor.CursorPosition != 0 {
		t.Errorf("expected cursor at 0 for empty document, got %d", TheState.Editor.CursorPosition)
	}
}

// TestCursorPositioning_IncompleteLayout verifies cursor positioning handles missing layout slices.
func TestCursorPositioning_IncompleteLayout(t *testing.T) {
	TheState = NewState()
	TheState.Editor.Buffer = "test"
	// GlyphLayout with ByteOffsets and X but no Advance (partial data)
	TheState.Editor.GlyphLayout = ui.GlyphLayout{
		ByteOffsets: []int{0, 1, 2, 3},
		X:           []ui.Dp{10, 20, 30, 40},
		Y:           []ui.Dp{70, 70, 70, 70},
		// Advance intentionally omitted
	}

	// Should not panic when Advance is missing
	SetCursorFromPoint(25, 70)
}

// TestHandleCursorMove_Bounds verifies cursor movement stays within buffer bounds.
func TestHandleCursorMove_Bounds(t *testing.T) {
	TheState = NewState()
	TheState.Editor.Buffer = "hello"
	TheState.Editor.CursorPosition = 0

	// Move right 3 times
	HandleCursorMove(1)
	HandleCursorMove(1)
	HandleCursorMove(1)
	if TheState.Editor.CursorPosition != 3 {
		t.Errorf("expected cursor at 3, got %d", TheState.Editor.CursorPosition)
	}

	// Move right past end — should clamp to buffer length
	HandleCursorMove(10)
	if TheState.Editor.CursorPosition != len(TheState.Editor.Buffer) {
		t.Errorf("expected cursor at %d (end of buffer), got %d", len(TheState.Editor.Buffer), TheState.Editor.CursorPosition)
	}

	// Move left past start — should clamp to 0
	HandleCursorMove(-100)
	if TheState.Editor.CursorPosition != 0 {
		t.Errorf("expected cursor at 0, got %d", TheState.Editor.CursorPosition)
	}
}

// TestTapLocalY_WindowRelative is a regression test for the tap-to-position-cursor
// coordinate bug: the tap's text-local Y must be WINDOW-relative (layout.Y==0 is
// the top of the visible window), so it must NOT include the full scroll offset.
// The old code added the full ScrollOffset, which made visualLine a huge
// content-line number that clamped the cursor to the bottom of the viewport on
// any large file.
func TestTapLocalY_WindowRelative(t *testing.T) {
	lh := float64(EditorLineHeight())
	// Tap 100 Dp below a region top that starts at 114 Dp, with a deep scroll
	// (a large file scrolled far down).
	got := tapLocalY(214, 114, 1539464)
	// Expected: (214-114) + (1539464 mod lineHeight) => in [100, 100+lineHeight).
	if got < 100 || got >= 100+lh {
		t.Errorf("tapLocalY = %v, want in [100, %v) (window-relative)", got, 100+lh)
	}
	// Regression: the buggy version returned ~1,539,564 (full scroll leaked in).
	if got > 1000 {
		t.Errorf("tapLocalY = %v, full scroll offset leaked in (must be window-relative)", got)
	}
}

// TestTapToPosition_WindowBaseOffset is a regression test for the
// window-relative GlyphLayout bug: the GlyphLayout is shaped from the visible
// window alone, so its ByteOffsets are relative to the window start
// (IMEWindowStartByte). SetCursorFromPoint must add that base to produce an
// absolute file offset. Before the fix, a tap on a scrolled large file set the
// cursor to a window-relative offset (near the file start), so the IME
// selection snapped to the window top on every tap.
func TestTapToPosition_WindowBaseOffset(t *testing.T) {
	lh := float64(EditorLineHeight())
	const lines = 40
	gl := ui.GlyphLayout{LineHeight: EditorLineHeight()}
	for i := 0; i < lines; i++ {
		for _, x := range []ui.Dp{10, 20} {
			gl.ByteOffsets = append(gl.ByteOffsets, i*2) // window-relative
			gl.X = append(gl.X, x)
			gl.Y = append(gl.Y, ui.Dp(float64(i+1)*lh))
			gl.Advance = append(gl.Advance, 10)
		}
	}
	TheState = NewState()
	TheState.Editor.GlyphLayout = gl
	TheState.Editor.IMEWindowStartByte = 47618 // window starts deep in the file
	TheState.ScrollOffset = 16500

	// Tap ~3 lines below the top of the window.
	regionTop := ui.Dp(114)
	ptY := regionTop + ui.Dp(3*lh)
	localY := tapLocalY(ptY, regionTop, TheState.ScrollOffset)
	SetCursorFromPoint(15, localY)

	// Window line 3 is window-relative byte 6, so the absolute cursor must be
	// base (47618) + 6 = 47624. Before the fix it would be 6 (window-relative),
	// which is the file start, not the tapped line.
	want := 47618 + 6
	if TheState.Editor.CursorPosition < want-2 || TheState.Editor.CursorPosition > want+2 {
		t.Errorf("cursor = %d, want %d (base 47618 + window byte 6); window-relative offset bug?", TheState.Editor.CursorPosition, want)
	}
	// Regression: the buggy cursor would be ~6 (window-relative, near file start).
	if TheState.Editor.CursorPosition < 100 {
		t.Errorf("cursor = %d, window-relative offset leaked (should be absolute ~%d)", TheState.Editor.CursorPosition, want)
	}
}

// TestTapToPosition_LargeFileScrolled is the end-to-end regression: with a
// window-relative GlyphLayout and a deep scroll, a tap a few lines below the top
// of the window must land on that window line, NOT be clamped to the last window
// line (the pre-fix behavior on large files).
func TestTapToPosition_LargeFileScrolled(t *testing.T) {
	lh := float64(EditorLineHeight())
	const lines = 40
	gl := ui.GlyphLayout{LineHeight: EditorLineHeight()}
	for i := 0; i < lines; i++ {
		for _, x := range []ui.Dp{10, 20} {
			gl.ByteOffsets = append(gl.ByteOffsets, i*2)
			gl.X = append(gl.X, x)
			gl.Y = append(gl.Y, ui.Dp(float64(i+1)*lh))
			gl.Advance = append(gl.Advance, 10)
		}
	}
	TheState = NewState()
	TheState.Editor.GlyphLayout = gl
	TheState.ScrollOffset = 1539464 // deep into a large file

	// Tap ~3 lines below the top of the window.
	regionTop := ui.Dp(114)
	ptY := regionTop + ui.Dp(3*lh)
	localY := tapLocalY(ptY, regionTop, TheState.ScrollOffset)
	SetCursorFromPoint(15, localY)

	// Should land on window line 3 (byte offset 6), NOT be clamped to the last
	// window line (line 39, byte offset 78).
	if TheState.Editor.CursorPosition < 4 || TheState.Editor.CursorPosition > 8 {
		t.Errorf("cursor = %d, want window line 3 (byte 6); large-file scroll clamp regression?", TheState.Editor.CursorPosition)
	}
}