package persistence

import (
	"bufio"
	"context"
	"fmt"
	"math"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/domain/errors"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/domain/ports"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/logging"
)

const (
	defaultLogFileName      = "main.log"
	logScannerInitialBuffer = 64 * 1024
	logScannerMaxBuffer     = 8 * 1024 * 1024
)

// LogRepository implements the ports.LogRepository interface
type LogRepository struct {
	cfg    *config.Config
	logDir string
	mu     sync.RWMutex
}

// NewLogRepository creates a new LogRepository
func NewLogRepository(cfg *config.Config) *LogRepository {
	return &LogRepository{
		cfg:    cfg,
		logDir: logging.ResolveLogDirectory(cfg),
	}
}

// ListLogFiles retrieves all log files
func (r *LogRepository) ListLogFiles(ctx context.Context) ([]*ports.LogFileInfo, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	if !r.IsLoggingEnabled() {
		return []*ports.LogFileInfo{}, nil
	}

	logDir := r.GetLogDirectory()
	if logDir == "" {
		return nil, errors.ErrLogDirectoryNotConfigured
	}

	entries, err := os.ReadDir(logDir)
	if err != nil {
		if os.IsNotExist(err) {
			return []*ports.LogFileInfo{}, nil
		}
		return nil, errors.Wrap(errors.InternalError, "failed to list log directory", err)
	}

	files := make([]*ports.LogFileInfo, 0)
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}

		name := entry.Name()
		if !strings.HasPrefix(name, "error-") || !strings.HasSuffix(name, ".log") {
			continue
		}

		info, err := entry.Info()
		if err != nil {
			continue
		}

		files = append(files, &ports.LogFileInfo{
			Name:     name,
			Size:     info.Size(),
			Modified: info.ModTime(),
		})
	}

	// Sort by modified time descending
	sort.Slice(files, func(i, j int) bool {
		return files[i].Modified.After(files[j].Modified)
	})

	return files, nil
}

// ReadLogFile reads a log file with optional filtering
func (r *LogRepository) ReadLogFile(ctx context.Context, filename string, after int64, limit int) (*ports.LogContent, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	if !r.IsLoggingEnabled() {
		return nil, errors.ErrLoggingDisabled
	}

	logDir := r.GetLogDirectory()
	if logDir == "" {
		return nil, errors.ErrLogDirectoryNotConfigured
	}

	// Collect all log files
	files, err := r.collectLogFiles(logDir)
	if err != nil {
		if os.IsNotExist(err) {
			return &ports.LogContent{
				Lines:           []string{},
				LineCount:       0,
				TotalLines:      0,
				LatestTimestamp: after,
			}, nil
		}
		return nil, errors.Wrap(errors.InternalError, "failed to collect log files", err)
	}

	// Accumulate lines
	acc := newLogAccumulator(after, limit)
	for _, file := range files {
		if err := acc.consumeFile(file); err != nil {
			return nil, errors.Wrap(errors.InternalError, fmt.Sprintf("failed to read log file %s", file), err)
		}
	}

	lines, total, latest := acc.result()
	if latest == 0 || latest < after {
		latest = after
	}

	return &ports.LogContent{
		Lines:           lines,
		LineCount:       len(lines),
		TotalLines:      total,
		LatestTimestamp: latest,
	}, nil
}

// DeleteLogFiles removes all log files and truncates the active log
func (r *LogRepository) DeleteLogFiles(ctx context.Context) (*ports.DeleteLogResult, error) {
	r.mu.Lock()
	defer r.mu.Unlock()

	if !r.IsLoggingEnabled() {
		return nil, errors.ErrLoggingDisabled
	}

	logDir := r.GetLogDirectory()
	if logDir == "" {
		return nil, errors.ErrLogDirectoryNotConfigured
	}

	entries, err := os.ReadDir(logDir)
	if err != nil {
		if os.IsNotExist(err) {
			return &ports.DeleteLogResult{
				Success: true,
				Message: "Log directory not found",
				Removed: 0,
			}, nil
		}
		return nil, errors.Wrap(errors.InternalError, "failed to list log directory", err)
	}

	removed := 0
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}

		name := entry.Name()
		fullPath := filepath.Join(logDir, name)

		if name == defaultLogFileName {
			// Truncate active log
			if err := os.Truncate(fullPath, 0); err != nil && !os.IsNotExist(err) {
				return nil, errors.Wrap(errors.InternalError, "failed to truncate log file", err)
			}
			continue
		}

		if r.isRotatedLogFile(name) {
			if err := os.Remove(fullPath); err != nil && !os.IsNotExist(err) {
				return nil, errors.Wrap(errors.InternalError, fmt.Sprintf("failed to remove %s", name), err)
			}
			removed++
		}
	}

	return &ports.DeleteLogResult{
		Success: true,
		Message: "Logs cleared successfully",
		Removed: removed,
	}, nil
}

// GetRequestErrorLogs retrieves error request log files
func (r *LogRepository) GetRequestErrorLogs(ctx context.Context) ([]*ports.LogFileInfo, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	// Return empty if request logging is enabled
	if r.cfg != nil && r.cfg.RequestLog {
		return []*ports.LogFileInfo{}, nil
	}

	logDir := r.GetLogDirectory()
	if logDir == "" {
		return nil, errors.ErrLogDirectoryNotConfigured
	}

	entries, err := os.ReadDir(logDir)
	if err != nil {
		if os.IsNotExist(err) {
			return []*ports.LogFileInfo{}, nil
		}
		return nil, errors.Wrap(errors.InternalError, "failed to list request error logs", err)
	}

	files := make([]*ports.LogFileInfo, 0)
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}

		name := entry.Name()
		if !strings.HasPrefix(name, "error-") || !strings.HasSuffix(name, ".log") {
			continue
		}

		info, err := entry.Info()
		if err != nil {
			continue
		}

		files = append(files, &ports.LogFileInfo{
			Name:     name,
			Size:     info.Size(),
			Modified: info.ModTime(),
		})
	}

	// Sort by modified time descending
	sort.Slice(files, func(i, j int) bool {
		return files[i].Modified.After(files[j].Modified)
	})

	return files, nil
}

// GetRequestLogByID retrieves a specific request log by ID
func (r *LogRepository) GetRequestLogByID(ctx context.Context, requestID string) ([]byte, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	logDir := r.GetLogDirectory()
	if logDir == "" {
		return nil, errors.ErrLogDirectoryNotConfigured
	}

	// Validate request ID
	requestID = strings.TrimSpace(requestID)
	if requestID == "" {
		return nil, errors.New(errors.InvalidInput, "request ID is required")
	}
	if strings.ContainsAny(requestID, "/\\") {
		return nil, errors.New(errors.InvalidInput, "invalid request ID")
	}

	entries, err := os.ReadDir(logDir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, errors.NewNotFoundError("log directory", logDir)
		}
		return nil, errors.Wrap(errors.InternalError, "failed to list log directory", err)
	}

	suffix := "-" + requestID + ".log"
	var matchedFile string
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}
		name := entry.Name()
		if strings.HasSuffix(name, suffix) {
			matchedFile = name
			break
		}
	}

	if matchedFile == "" {
		return nil, errors.NewNotFoundError("log file for request ID", requestID)
	}

	// Security check - ensure file is within log directory
	dirAbs, err := filepath.Abs(logDir)
	if err != nil {
		return nil, errors.Wrap(errors.InternalError, "failed to resolve log directory", err)
	}
	fullPath := filepath.Clean(filepath.Join(dirAbs, matchedFile))
	prefix := dirAbs + string(os.PathSeparator)
	if !strings.HasPrefix(fullPath, prefix) {
		return nil, errors.New(errors.InvalidInput, "invalid log file path")
	}

	// Read file
	data, err := os.ReadFile(fullPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, errors.NewNotFoundError("log file", matchedFile)
		}
		return nil, errors.Wrap(errors.InternalError, "failed to read log file", err)
	}

	return data, nil
}

// DownloadRequestErrorLog downloads a specific error log file
func (r *LogRepository) DownloadRequestErrorLog(ctx context.Context, filename string) ([]byte, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	logDir := r.GetLogDirectory()
	if logDir == "" {
		return nil, errors.ErrLogDirectoryNotConfigured
	}

	// Validate filename
	filename = strings.TrimSpace(filename)
	if filename == "" || strings.Contains(filename, "/") || strings.Contains(filename, "\\") {
		return nil, errors.New(errors.InvalidInput, "invalid log file name")
	}

	if !strings.HasPrefix(filename, "error-") || !strings.HasSuffix(filename, ".log") {
		return nil, errors.NewNotFoundError("log file", filename)
	}

	// Security check
	dirAbs, err := filepath.Abs(logDir)
	if err != nil {
		return nil, errors.Wrap(errors.InternalError, "failed to resolve log directory", err)
	}
	fullPath := filepath.Clean(filepath.Join(dirAbs, filename))
	prefix := dirAbs + string(os.PathSeparator)
	if !strings.HasPrefix(fullPath, prefix) {
		return nil, errors.New(errors.InvalidInput, "invalid log file path")
	}

	// Check if file exists and is not a directory
	info, err := os.Stat(fullPath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, errors.NewNotFoundError("log file", filename)
		}
		return nil, errors.Wrap(errors.InternalError, "failed to stat log file", err)
	}
	if info.IsDir() {
		return nil, errors.New(errors.InvalidInput, "invalid log file")
	}

	// Read file
	data, err := os.ReadFile(fullPath)
	if err != nil {
		return nil, errors.Wrap(errors.InternalError, "failed to read log file", err)
	}

	return data, nil
}

// GetLogDirectory returns the log directory path
func (r *LogRepository) GetLogDirectory() string {
	r.mu.RLock()
	defer r.mu.RUnlock()

	if r.logDir != "" {
		return r.logDir
	}

	if r.cfg != nil {
		return logging.ResolveLogDirectory(r.cfg)
	}

	return ""
}

// IsLoggingEnabled returns whether logging to file is enabled
func (r *LogRepository) IsLoggingEnabled() bool {
	r.mu.RLock()
	defer r.mu.RUnlock()

	if r.cfg == nil {
		return false
	}
	return r.cfg.LoggingToFile
}

// SetConfig updates the configuration
func (r *LogRepository) SetConfig(cfg *config.Config) {
	r.mu.Lock()
	defer r.mu.Unlock()
	r.cfg = cfg
	r.logDir = logging.ResolveLogDirectory(cfg)
}

// collectLogFiles collects all log files in order
func (r *LogRepository) collectLogFiles(dir string) ([]string, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, err
	}

	type candidate struct {
		path  string
		order int64
	}

	cands := make([]candidate, 0, len(entries))
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}

		name := entry.Name()
		if name == defaultLogFileName {
			cands = append(cands, candidate{path: filepath.Join(dir, name), order: 0})
			continue
		}

		if order, ok := r.rotationOrder(name); ok {
			cands = append(cands, candidate{path: filepath.Join(dir, name), order: order})
		}
	}

	if len(cands) == 0 {
		return []string{}, nil
	}

	// Sort by order
	sort.Slice(cands, func(i, j int) bool {
		return cands[i].order < cands[j].order
	})

	// Reverse to get newest first
	paths := make([]string, 0, len(cands))
	for i := len(cands) - 1; i >= 0; i-- {
		paths = append(paths, cands[i].path)
	}

	return paths, nil
}

// isRotatedLogFile checks if a file is a rotated log file
func (r *LogRepository) isRotatedLogFile(name string) bool {
	_, ok := r.rotationOrder(name)
	return ok
}

// rotationOrder determines the rotation order of a log file
func (r *LogRepository) rotationOrder(name string) (int64, bool) {
	if order, ok := r.numericRotationOrder(name); ok {
		return order, true
	}
	if order, ok := r.timestampRotationOrder(name); ok {
		return order, true
	}
	return 0, false
}

// numericRotationOrder extracts numeric rotation order
func (r *LogRepository) numericRotationOrder(name string) (int64, bool) {
	if !strings.HasPrefix(name, defaultLogFileName+".") {
		return 0, false
	}
	suffix := strings.TrimPrefix(name, defaultLogFileName+".")
	if suffix == "" {
		return 0, false
	}
	n, err := strconv.Atoi(suffix)
	if err != nil {
		return 0, false
	}
	return int64(n), true
}

// timestampRotationOrder extracts timestamp rotation order
func (r *LogRepository) timestampRotationOrder(name string) (int64, bool) {
	ext := filepath.Ext(defaultLogFileName)
	base := strings.TrimSuffix(defaultLogFileName, ext)
	if base == "" {
		return 0, false
	}

	prefix := base + "-"
	if !strings.HasPrefix(name, prefix) {
		return 0, false
	}

	clean := strings.TrimPrefix(name, prefix)
	if strings.HasSuffix(clean, ".gz") {
		clean = strings.TrimSuffix(clean, ".gz")
	}
	if ext != "" {
		if !strings.HasSuffix(clean, ext) {
			return 0, false
		}
		clean = strings.TrimSuffix(clean, ext)
	}
	if clean == "" {
		return 0, false
	}

	// Remove any suffix after timestamp
	if idx := strings.IndexByte(clean, '.'); idx != -1 {
		clean = clean[:idx]
	}

	parsed, err := time.ParseInLocation("2006-01-02T15-04-05", clean, time.Local)
	if err != nil {
		return 0, false
	}

	return math.MaxInt64 - parsed.Unix(), true
}

// logAccumulator accumulates log lines
type logAccumulator struct {
	cutoff  int64
	limit   int
	lines   []string
	total   int
	latest  int64
	include bool
}

// newLogAccumulator creates a new log accumulator
func newLogAccumulator(cutoff int64, limit int) *logAccumulator {
	capacity := 256
	if limit > 0 && limit < capacity {
		capacity = limit
	}
	return &logAccumulator{
		cutoff: cutoff,
		limit:  limit,
		lines:  make([]string, 0, capacity),
	}
}

// consumeFile reads and accumulates lines from a file
func (acc *logAccumulator) consumeFile(path string) error {
	file, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	buf := make([]byte, 0, logScannerInitialBuffer)
	scanner.Buffer(buf, logScannerMaxBuffer)

	for scanner.Scan() {
		acc.addLine(scanner.Text())
	}

	return scanner.Err()
}

// addLine adds a line to the accumulator
func (acc *logAccumulator) addLine(raw string) {
	line := strings.TrimRight(raw, "\r")
	acc.total++

	ts := parseTimestamp(line)
	if ts > acc.latest {
		acc.latest = ts
	}

	if ts > 0 {
		acc.include = acc.cutoff == 0 || ts > acc.cutoff
		if acc.cutoff == 0 || acc.include {
			acc.append(line)
		}
		return
	}

	if acc.cutoff == 0 || acc.include {
		acc.append(line)
	}
}

// append adds a line to the lines slice
func (acc *logAccumulator) append(line string) {
	acc.lines = append(acc.lines, line)
	if acc.limit > 0 && len(acc.lines) > acc.limit {
		acc.lines = acc.lines[len(acc.lines)-acc.limit:]
	}
}

// result returns the accumulated result
func (acc *logAccumulator) result() ([]string, int, int64) {
	if acc.lines == nil {
		acc.lines = []string{}
	}
	return acc.lines, acc.total, acc.latest
}

// parseTimestamp parses a timestamp from a log line
func parseTimestamp(line string) int64 {
	if strings.HasPrefix(line, "[") {
		line = line[1:]
	}
	if len(line) < 19 {
		return 0
	}

	candidate := line[:19]
	t, err := time.ParseInLocation("2006-01-02 15:04:05", candidate, time.Local)
	if err != nil {
		return 0
	}

	return t.Unix()
}

// Ensure LogRepository implements the interface
var _ ports.LogRepository = (*LogRepository)(nil)