package editor

import (
	"fmt"
	"testing"

	"git.gophernest.net/azpect/TextEditor/internal/action"
)

// NOTE: AI Generated tests

// generateLines creates n lines of content
func generateLines(n int) []string {
	lines := make([]string, n)
	for i := range n {
		lines[i] = fmt.Sprintf("line %d", i+1)
	}
	return lines
}

func TestScrollBasic(t *testing.T) {
	t.Run("small file does not scroll", func(t *testing.T) {
		// 10 lines, viewport 24 -> no scrolling needed
		lines := generateLines(10)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 0}, 80, 24)
		sendKeys(tm, "G") // go to bottom

		m := getFinalModel(t, tm)
		if m.ScrollY() != 0 {
			t.Errorf("ScrollY() = %d, want 0", m.ScrollY())
		}
	})

	t.Run("scrolls down when cursor moves past bottom margin", func(t *testing.T) {
		// 50 lines, viewport 20, scrollOff 8
		// Viewport shows lines 0-18 (19 lines, -1 for status bar)
		// Safe zone: lines 8 to 10 (19-1-8=10)
		// Moving to line 11+ should trigger scroll
		lines := generateLines(50)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 0}, 80, 20)

		// Move down 15 times to get to line 15
		for range 15 {
			sendKeys(tm, "j")
		}

		m := getFinalModel(t, tm)
		if m.CursorY() != 15 {
			t.Errorf("CursorY() = %d, want 15", m.CursorY())
		}
		// With scrollOff=8, viewport=19, cursor at 15 means:
		// cursor should be at position 10 from top (19-1-8=10)
		// so scrollY = 15 - 10 = 5
		if m.ScrollY() < 1 {
			t.Errorf("ScrollY() = %d, want > 0 (should have scrolled)", m.ScrollY())
		}
	})

	t.Run("scrolls up when cursor moves past top margin", func(t *testing.T) {
		// Start at line 20, move up
		lines := generateLines(50)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 20}, 80, 20)

		// First, let the model adjust (it will scroll to show cursor)
		// Then move up 15 times
		for range 15 {
			sendKeys(tm, "k")
		}

		m := getFinalModel(t, tm)
		if m.CursorY() != 5 {
			t.Errorf("CursorY() = %d, want 5", m.CursorY())
		}
		// Cursor at line 5 with scrollOff=8 means scrollY should be 0
		// (can't scroll negative, and cursor is within safe zone from top)
		if m.ScrollY() != 0 {
			t.Errorf("ScrollY() = %d, want 0", m.ScrollY())
		}
	})

	t.Run("G jumps to bottom and scrolls", func(t *testing.T) {
		lines := generateLines(100)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 0}, 80, 20)
		sendKeys(tm, "G")

		m := getFinalModel(t, tm)
		if m.CursorY() != 99 {
			t.Errorf("CursorY() = %d, want 99", m.CursorY())
		}
		// With 100 lines and viewport 19, max scrollY = 100 - 19 = 81
		// Cursor at 99 with scrollOff=8 means cursor at position 10 from top
		// scrollY = 99 - 10 = 89, but clamped to maxScroll = 81
		if m.ScrollY() != 81 {
			t.Errorf("ScrollY() = %d, want 81", m.ScrollY())
		}
	})

	t.Run("gg jumps to top and scrolls", func(t *testing.T) {
		lines := generateLines(100)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 50}, 80, 20)
		sendKeys(tm, "g", "g")

		m := getFinalModel(t, tm)
		if m.CursorY() != 0 {
			t.Errorf("CursorY() = %d, want 0", m.CursorY())
		}
		if m.ScrollY() != 0 {
			t.Errorf("ScrollY() = %d, want 0", m.ScrollY())
		}
	})
}

func TestScrollEdgeCases(t *testing.T) {
	t.Run("scrollY never goes negative", func(t *testing.T) {
		lines := generateLines(50)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 0}, 80, 20)

		// Try to move up from top
		for range 5 {
			sendKeys(tm, "k")
		}

		m := getFinalModel(t, tm)
		if m.ScrollY() < 0 {
			t.Errorf("ScrollY() = %d, want >= 0", m.ScrollY())
		}
	})

	t.Run("scrollY clamped to max scroll", func(t *testing.T) {
		lines := generateLines(30)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 0}, 80, 20)
		sendKeys(tm, "G")

		m := getFinalModel(t, tm)
		// 30 lines, viewport 19 -> maxScroll = 30 - 19 = 11
		maxScroll := 30 - 19
		if m.ScrollY() > maxScroll {
			t.Errorf("ScrollY() = %d, want <= %d", m.ScrollY(), maxScroll)
		}
	})

	t.Run("cursor stays visible after delete at bottom", func(t *testing.T) {
		lines := generateLines(30)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 29}, 80, 20)

		// Delete some lines at bottom
		sendKeys(tm, "d", "d", "d", "d")

		m := getFinalModel(t, tm)
		// Cursor should still be visible
		viewportHeight := 19
		if m.CursorY() < m.ScrollY() || m.CursorY() >= m.ScrollY()+viewportHeight {
			t.Errorf("Cursor at %d not visible in viewport [%d, %d)",
				m.CursorY(), m.ScrollY(), m.ScrollY()+viewportHeight)
		}
	})
}

func TestScrollWithCount(t *testing.T) {
	t.Run("5j scrolls appropriately", func(t *testing.T) {
		lines := generateLines(50)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 5}, 80, 20)

		sendKeys(tm, "1", "0", "j") // move down 10 lines

		m := getFinalModel(t, tm)
		if m.CursorY() != 15 {
			t.Errorf("CursorY() = %d, want 15", m.CursorY())
		}
		// Should have scrolled since we moved past the safe zone
		if m.ScrollY() == 0 {
			t.Errorf("ScrollY() = %d, want > 0", m.ScrollY())
		}
	})

	t.Run("5k scrolls appropriately", func(t *testing.T) {
		lines := generateLines(50)
		tm := newTestModelWithTermSize(t, lines, action.Position{Col: 0, Line: 25}, 80, 20)

		sendKeys(tm, "1", "5", "k") // move up 15 lines

		m := getFinalModel(t, tm)
		if m.CursorY() != 10 {
			t.Errorf("CursorY() = %d, want 10", m.CursorY())
		}
	})
}