package browser

import (
	"testing"
)

// --- Test: Scroll Clamp Minimum ---

func TestScrollClamp_Minimum(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 500
	s.VisibleCount = 20

	// Set scroll index below minimum
	s.ScrollIndex = -10

	// Apply scroll clamp
	HandleScroll(s, -5)

	// ScrollIndex should be clamped to 0
	if s.ScrollIndex != 0 {
		t.Errorf("expected ScrollIndex=0 (clamped), got %d", s.ScrollIndex)
	}
}

// --- Test: Scroll Clamp Maximum ---

func TestScrollClamp_Maximum(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 500
	s.VisibleCount = 20

	// Set scroll index above maximum
	s.ScrollIndex = 1000

	// Apply scroll clamp
	HandleScroll(s, 100)

	// ScrollIndex should be clamped to max (TotalEntries - VisibleCount)
	maxScroll := s.TotalEntries - s.VisibleCount
	if s.ScrollIndex != maxScroll {
		t.Errorf("expected ScrollIndex=%d (clamped to max), got %d", maxScroll, s.ScrollIndex)
	}
}

// --- Test: Scroll Delta Computation ---

func TestScrollDelta_Computation(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 1000
	s.VisibleCount = 20
	s.ScrollIndex = 100

	// Scroll down by 5 entries (positive delta)
	HandleScroll(s, 5)

	if s.ScrollIndex != 105 {
		t.Errorf("expected ScrollIndex=105 after scrolling down 5, got %d", s.ScrollIndex)
	}

	// Scroll up by 3 entries (negative delta)
	HandleScroll(s, -3)

	if s.ScrollIndex != 102 {
		t.Errorf("expected ScrollIndex=102 after scrolling up 3, got %d", s.ScrollIndex)
	}
}

// --- Test: Scroll Prefetch Triggered ---

func TestScroll_PrefetchTriggered(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 2000
	s.VisibleCount = 20
	s.ScrollIndex = 500 // Page 5

	// Load some pages around current position
	entries := make([]Entry, 2000)
	for i := 0; i < 2000; i++ {
		entries[i] = NewEntry("/test/file.txt", "file.txt", 100, s.TapTimestamp, false)
	}
	// Build position map for the default sort mode (NameAsc)
	s.SortIndex = &DirectoryIndex{
		Entries:    entries,
		SortOrders: map[string][]int{"name_asc": buildPositionMap(entries, SortModeNameAsc)},
	}
	for pageIdx := 3; pageIdx <= 7; pageIdx++ {
		p := loadPageFromIndex(s, pageIdx)
		if p != nil {
			s.Pages[pageIdx] = p
		}
	}

	// Record current page count
	pagesBefore := len(s.Pages)

	// Scroll to trigger prefetch
	HandleScroll(s, 200) // Scroll to page 7+

	// After scroll, prefetch should have been triggered
	// (exact behavior depends on implementation)
	// For now, verify that scroll happened correctly
	if s.ScrollIndex <= 500 {
		t.Errorf("expected ScrollIndex > 500 after scrolling, got %d", s.ScrollIndex)
	}

	// Page count may have increased due to prefetch
	if len(s.Pages) < pagesBefore {
		t.Errorf("expected page count to not decrease after scroll, before=%d, after=%d", pagesBefore, len(s.Pages))
	}
}

// --- Test: Scroll Eviction Triggered ---

func TestScroll_EvictionTriggered(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 5000
	s.VisibleCount = 20
	s.ScrollIndex = 0

	// Load pages at various positions
	entries := make([]Entry, 5000)
	for i := 0; i < 5000; i++ {
		entries[i] = NewEntry("/test/file.txt", "file.txt", 100, s.TapTimestamp, false)
	}
	// Build position map for the default sort mode (NameAsc)
	s.SortIndex = &DirectoryIndex{
		Entries:    entries,
		SortOrders: map[string][]int{"name_asc": buildPositionMap(entries, SortModeNameAsc)},
	}
	for pageIdx := 0; pageIdx <= 10; pageIdx++ {
		p := loadPageFromIndex(s, pageIdx)
		if p != nil {
			s.Pages[pageIdx] = p
		}
	}

	// Scroll far away from initial position
	HandleScroll(s, 4000) // Scroll to page 40+

	// Pages far from current position should be evicted
	// Check that page 0 was evicted (it's far from page 40)
	if page, exists := s.Pages[0]; exists && page.Loaded {
		t.Error("expected page 0 to be evicted after scrolling far away")
	}
}

// --- Test: Scroll With Search Results ---

func TestScroll_WithSearchResults(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 100
	s.VisibleCount = 20
	s.ScrollIndex = 0

	// Set up search results
	s.SearchResults = []int{5, 15, 25, 35, 45}

	// Scroll should work normally even with search results
	HandleScroll(s, 10)

	if s.ScrollIndex != 10 {
		t.Errorf("expected ScrollIndex=10, got %d", s.ScrollIndex)
	}
}

// --- Test: Scroll To Beginning ---

func TestScroll_ToBeginning(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 1000
	s.VisibleCount = 20
	s.ScrollIndex = 500

	// Scroll all the way to the beginning
	HandleScroll(s, -500)

	if s.ScrollIndex != 0 {
		t.Errorf("expected ScrollIndex=0 at beginning, got %d", s.ScrollIndex)
	}
}

// --- Test: Scroll To End ---

func TestScroll_ToEnd(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 1000
	s.VisibleCount = 20
	s.ScrollIndex = 0

	// Scroll all the way to the end
	HandleScroll(s, 1000)

	maxScroll := s.TotalEntries - s.VisibleCount
	if s.ScrollIndex != maxScroll {
		t.Errorf("expected ScrollIndex=%d at end, got %d", maxScroll, s.ScrollIndex)
	}
}

// --- Test: Scroll With Small Directory ---

func TestScroll_SmallDirectory(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 10 // Smaller than VisibleCount
	s.VisibleCount = 20
	s.ScrollIndex = 0

	// Try to scroll down (should be clamped)
	HandleScroll(s, 100)

	// ScrollIndex should be 0 (can't scroll beyond available entries)
	if s.ScrollIndex != 0 {
		t.Errorf("expected ScrollIndex=0 for small directory, got %d", s.ScrollIndex)
	}
}

// --- Test: Scroll Prefetch Triggered On Page Boundary ---

func TestScroll_PrefetchTriggeredOnPageBoundary(t *testing.T) {
	s := NewBrowserState()
	s.TotalEntries = 500
	s.VisibleCount = 20
	s.ScrollIndex = 90 // Near page boundary (page 0 ends at 100)

	// Load page 0
	entries := make([]Entry, 500)
	for i := 0; i < 500; i++ {
		entries[i] = NewEntry("/test/file.txt", "file.txt", 100, s.TapTimestamp, false)
	}
	// Build position map for the default sort mode (NameAsc)
	s.SortIndex = &DirectoryIndex{
		Entries:    entries,
		SortOrders: map[string][]int{"name_asc": buildPositionMap(entries, SortModeNameAsc)},
	}
	s.Pages[0] = loadPageFromIndex(s, 0)

	// Scroll across page boundary
	HandleScroll(s, 15) // Should cross into page 1

	// Verify scroll happened
	if s.ScrollIndex != 105 {
		t.Errorf("expected ScrollIndex=105, got %d", s.ScrollIndex)
	}
}