package database

import (
	"context"
	"database/sql"
	"net"
	"sync"
	"testing"
	"time"

	"git.eeqj.de/sneak/routewatch/internal/config"
	"git.eeqj.de/sneak/routewatch/internal/logger"
)

// tempStoreMemory is the PRAGMA temp_store value meaning "hold temp B-trees in
// memory"; the DSN change must leave temp_store below this so they spill to disk.
const tempStoreMemory = 2

// heldConnections is how many pooled connections the pragma test holds open at
// once so each is a distinct SQLite connection that parsed the DSN.
const heldConnections = 5

// Parameters for the checkpoint-contention regression test.
const (
	// contentionIterations is how many batch writes race the checkpoint loop.
	contentionIterations = 400
	// contendedASNCount is the small set of ASNs the batches reuse, so most
	// batches update existing rows and exercise the read-before-write path.
	contendedASNCount = 16
	// asnSecondBand offsets a second ASN per batch so each batch writes more
	// than one row.
	asnSecondBand = 100
)

func TestIPToUint32(t *testing.T) {
	tests := []struct {
		name     string
		ip       string
		expected uint32
	}{
		{
			name:     "Simple IP",
			ip:       "192.168.1.1",
			expected: 3232235777, // 192<<24 + 168<<16 + 1<<8 + 1
		},
		{
			name:     "Minimum IP",
			ip:       "0.0.0.0",
			expected: 0,
		},
		{
			name:     "Maximum IP",
			ip:       "255.255.255.255",
			expected: 4294967295,
		},
		{
			name:     "10.0.0.0",
			ip:       "10.0.0.0",
			expected: 167772160,
		},
		{
			name:     "172.16.0.0",
			ip:       "172.16.0.0",
			expected: 2886729728,
		},
		{
			name:     "8.8.8.8",
			ip:       "8.8.8.8",
			expected: 134744072,
		},
		{
			name:     "1.2.3.4",
			ip:       "1.2.3.4",
			expected: 16909060,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			ip := net.ParseIP(tt.ip)
			if ip == nil {
				t.Fatalf("Failed to parse IP: %s", tt.ip)
			}

			result := ipToUint32(ip)
			if result != tt.expected {
				t.Errorf("ipToUint32(%s) = %d, want %d", tt.ip, result, tt.expected)
			}

			// Test with IPv4-mapped IPv6 address
			ip6 := net.ParseIP(tt.ip).To16()
			if ip6 != nil {
				result6 := ipToUint32(ip6)
				if result6 != tt.expected {
					t.Errorf("ipToUint32(%s as IPv6) = %d, want %d", tt.ip, result6, tt.expected)
				}
			}
		})
	}
}

func TestCalculateIPv4Range(t *testing.T) {
	tests := []struct {
		name      string
		cidr      string
		wantStart uint32
		wantEnd   uint32
		wantErr   bool
	}{
		{
			name:      "Single IP /32",
			cidr:      "192.168.1.1/32",
			wantStart: 3232235777,
			wantEnd:   3232235777,
		},
		{
			name:      "Class C /24",
			cidr:      "192.168.1.0/24",
			wantStart: 3232235776, // 192.168.1.0
			wantEnd:   3232236031, // 192.168.1.255
		},
		{
			name:      "Class B /16",
			cidr:      "192.168.0.0/16",
			wantStart: 3232235520, // 192.168.0.0
			wantEnd:   3232301055, // 192.168.255.255
		},
		{
			name:      "Class A /8",
			cidr:      "10.0.0.0/8",
			wantStart: 167772160, // 10.0.0.0
			wantEnd:   184549375, // 10.255.255.255
		},
		{
			name:      "Entire IPv4 space /0",
			cidr:      "0.0.0.0/0",
			wantStart: 0,
			wantEnd:   4294967295,
		},
		{
			name:      "Small subnet /30",
			cidr:      "192.168.1.0/30",
			wantStart: 3232235776, // 192.168.1.0
			wantEnd:   3232235779, // 192.168.1.3
		},
		{
			name:      "Medium subnet /20",
			cidr:      "172.16.0.0/20",
			wantStart: 2886729728, // 172.16.0.0
			wantEnd:   2886733823, // 172.16.15.255
		},
		{
			name:      "Private range 172.16/12",
			cidr:      "172.16.0.0/12",
			wantStart: 2886729728, // 172.16.0.0
			wantEnd:   2887778303, // 172.31.255.255
		},
		{
			name:      "Google DNS /29",
			cidr:      "8.8.8.8/29",
			wantStart: 134744072, // 8.8.8.8 (network is actually 8.8.8.8 with /29)
			wantEnd:   134744079, // 8.8.8.15
		},
		{
			name:      "Non-zero host bits",
			cidr:      "192.168.1.5/24",
			wantStart: 3232235776, // 192.168.1.0 (network address)
			wantEnd:   3232236031, // 192.168.1.255
		},
		{
			name:    "Invalid CIDR",
			cidr:    "192.168.1.1/33",
			wantErr: true,
		},
		{
			name:    "Invalid IP",
			cidr:    "256.256.256.256/24",
			wantErr: true,
		},
		{
			name:    "IPv6 CIDR",
			cidr:    "2001:db8::/32",
			wantErr: true,
		},
		{
			name:    "Empty CIDR",
			cidr:    "",
			wantErr: true,
		},
		{
			name:    "Missing mask",
			cidr:    "192.168.1.1",
			wantErr: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			start, end, err := CalculateIPv4Range(tt.cidr)

			if tt.wantErr {
				if err == nil {
					t.Errorf("CalculateIPv4Range(%s) expected error, got nil", tt.cidr)
				}
				return
			}

			if err != nil {
				t.Errorf("CalculateIPv4Range(%s) unexpected error: %v", tt.cidr, err)
				return
			}

			if start != tt.wantStart {
				t.Errorf("CalculateIPv4Range(%s) start = %d, want %d", tt.cidr, start, tt.wantStart)
			}

			if end != tt.wantEnd {
				t.Errorf("CalculateIPv4Range(%s) end = %d, want %d", tt.cidr, end, tt.wantEnd)
			}

			// Verify that start <= end
			if start > end {
				t.Errorf("CalculateIPv4Range(%s) start (%d) > end (%d)", tt.cidr, start, end)
			}

			// Verify the range size matches the CIDR mask
			if !tt.wantErr && tt.cidr != "" {
				_, ipNet, _ := net.ParseCIDR(tt.cidr)
				if ipNet != nil {
					ones, bits := ipNet.Mask.Size()
					expectedSize := uint32(1) << uint(bits-ones)
					actualSize := end - start + 1
					if actualSize != expectedSize {
						t.Errorf("CalculateIPv4Range(%s) range size = %d, want %d", tt.cidr, actualSize, expectedSize)
					}
				}
			}
		})
	}
}

func TestIPv4RangeIntegration(t *testing.T) {
	// Test that our functions work correctly together
	tests := []struct {
		name          string
		cidr          string
		testIPs       []string
		shouldContain []bool
	}{
		{
			name: "192.168.1.0/24",
			cidr: "192.168.1.0/24",
			testIPs: []string{
				"192.168.1.0",
				"192.168.1.1",
				"192.168.1.255",
				"192.168.0.255",
				"192.168.2.0",
			},
			shouldContain: []bool{true, true, true, false, false},
		},
		{
			name: "10.0.0.0/8",
			cidr: "10.0.0.0/8",
			testIPs: []string{
				"10.0.0.0",
				"10.255.255.255",
				"10.1.2.3",
				"9.255.255.255",
				"11.0.0.0",
			},
			shouldContain: []bool{true, true, true, false, false},
		},
		{
			name: "172.16.0.0/12",
			cidr: "172.16.0.0/12",
			testIPs: []string{
				"172.16.0.0",
				"172.31.255.255",
				"172.20.1.1",
				"172.15.255.255",
				"172.32.0.0",
			},
			shouldContain: []bool{true, true, true, false, false},
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			start, end, err := CalculateIPv4Range(tt.cidr)
			if err != nil {
				t.Fatalf("Failed to calculate range for %s: %v", tt.cidr, err)
			}

			for i, testIP := range tt.testIPs {
				ip := net.ParseIP(testIP)
				if ip == nil {
					t.Fatalf("Failed to parse test IP: %s", testIP)
				}

				ipUint := ipToUint32(ip)
				contained := ipUint >= start && ipUint <= end

				if contained != tt.shouldContain[i] {
					t.Errorf("IP %s in range %s: got %v, want %v", testIP, tt.cidr, contained, tt.shouldContain[i])
				}
			}
		})
	}
}

// TestConnectionPoolPragmas holds several pooled connections open at once and
// checks each one carries the per-connection settings from the DSN, plus the
// process-wide hard heap limit.
func TestConnectionPoolPragmas(t *testing.T) {
	cfg := &config.Config{StateDir: t.TempDir()}

	db, err := New(cfg, logger.New())
	if err != nil {
		t.Fatalf("failed to create database: %v", err)
	}
	defer func() { _ = db.Close() }()

	ctx := context.Background()

	// Hold distinct connections open simultaneously so the pool must open a new
	// one (each parsing the DSN) rather than hand back the same connection.
	conns := make([]*sql.Conn, 0, heldConnections)
	defer func() {
		for _, c := range conns {
			_ = c.Close()
		}
	}()

	for i := 0; i < heldConnections; i++ {
		c, err := db.db.Conn(ctx)
		if err != nil {
			t.Fatalf("failed to open connection %d: %v", i, err)
		}
		conns = append(conns, c)
	}

	for i, c := range conns {
		var cacheSize int
		if err := c.QueryRowContext(ctx, "PRAGMA cache_size").Scan(&cacheSize); err != nil {
			t.Fatalf("conn %d: failed to read cache_size: %v", i, err)
		}
		if cacheSize != sqliteCacheSizeKiB {
			t.Errorf("conn %d: cache_size = %d, want %d", i, cacheSize, sqliteCacheSizeKiB)
		}

		var busyTimeout int
		if err := c.QueryRowContext(ctx, "PRAGMA busy_timeout").Scan(&busyTimeout); err != nil {
			t.Fatalf("conn %d: failed to read busy_timeout: %v", i, err)
		}
		if busyTimeout != sqliteBusyTimeoutMs {
			t.Errorf("conn %d: busy_timeout = %d, want %d", i, busyTimeout, sqliteBusyTimeoutMs)
		}

		var tempStore int
		if err := c.QueryRowContext(ctx, "PRAGMA temp_store").Scan(&tempStore); err != nil {
			t.Fatalf("conn %d: failed to read temp_store: %v", i, err)
		}
		if tempStore == tempStoreMemory {
			t.Errorf("conn %d: temp_store = %d, want anything but %d (MEMORY)", i, tempStore, tempStoreMemory)
		}

		var hardHeapLimit int64
		if err := c.QueryRowContext(ctx, "PRAGMA hard_heap_limit").Scan(&hardHeapLimit); err != nil {
			t.Fatalf("conn %d: failed to read hard_heap_limit: %v", i, err)
		}
		if hardHeapLimit != sqliteHardHeapLimitBytes {
			t.Errorf("conn %d: hard_heap_limit = %d, want %d", i, hardHeapLimit, sqliteHardHeapLimitBytes)
		}
	}
}

// TestBatchWriteDuringCheckpoint reproduces issue #25. A batch write reads
// (SELECT) before it writes (INSERT/UPDATE). Under the default deferred locking
// the transaction begins as a reader and, when the maintainer's WAL checkpoint
// holds the write lock, its upgrade to writer fails immediately with "database
// is locked" without honouring busy_timeout, dropping the batch. With
// _txlock=immediate the transaction takes the write lock at BEGIN and waits, so
// no batch is dropped. The checkpoint runs without the Database mutex, exactly
// as the background maintainer does in production.
func TestBatchWriteDuringCheckpoint(t *testing.T) {
	cfg := &config.Config{StateDir: t.TempDir()}

	db, err := New(cfg, logger.New())
	if err != nil {
		t.Fatalf("failed to create database: %v", err)
	}
	defer func() { _ = db.Close() }()

	ctx, cancel := context.WithCancel(context.Background())

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		for {
			select {
			case <-ctx.Done():
				return
			default:
				_ = db.Checkpoint(ctx) // errors are the checkpoint's own to absorb
			}
		}
	}()

	ts := time.Now().UTC()
	for i := 0; i < contentionIterations; i++ {
		asns := map[int]time.Time{
			i % contendedASNCount:                   ts,
			(i % contendedASNCount) + asnSecondBand: ts,
		}
		if err := db.GetOrCreateASNBatch(asns); err != nil {
			cancel()
			wg.Wait()
			t.Fatalf("batch write failed under checkpoint contention: %v", err)
		}
	}

	cancel()
	wg.Wait()
}

func BenchmarkIPToUint32(b *testing.B) {
	ip := net.ParseIP("192.168.1.1")
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_ = ipToUint32(ip)
	}
}

func BenchmarkCalculateIPv4Range(b *testing.B) {
	cidr := "192.168.0.0/16"
	b.ResetTimer()

	for i := 0; i < b.N; i++ {
		_, _, _ = CalculateIPv4Range(cidr)
	}
}