internal/logging/request_logger.go

// Package logging provides request logging functionality for the CLI Proxy API server.
// It handles capturing and storing detailed HTTP request and response data when enabled
// through configuration, supporting both regular and streaming responses.
package logging

import (
	"bytes"
	"compress/flate"
	"compress/gzip"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"sync/atomic"
	"time"

	"github.com/andybalholm/brotli"
	"github.com/klauspost/compress/zstd"
	log "github.com/sirupsen/logrus"

	"github.com/router-for-me/CLIProxyAPI/v6/internal/buildinfo"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/interfaces"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
)

var requestLogID atomic.Uint64

// RequestLogger defines the interface for logging HTTP requests and responses.
// It provides methods for logging both regular and streaming HTTP request/response cycles.
type RequestLogger interface {
	// LogRequest logs a complete non-streaming request/response cycle.
	//
	// Parameters:
	//   - url: The request URL
	//   - method: The HTTP method
	//   - requestHeaders: The request headers
	//   - body: The request body
	//   - statusCode: The response status code
	//   - responseHeaders: The response headers
	//   - response: The raw response data
	//   - apiRequest: The API request data
	//   - apiResponse: The API response data
	//   - requestID: Optional request ID for log file naming
	//
	// Returns:
	//   - error: An error if logging fails, nil otherwise
	LogRequest(url, method string, requestHeaders map[string][]string, body []byte, statusCode int, responseHeaders map[string][]string, response, apiRequest, apiResponse []byte, apiResponseErrors []*interfaces.ErrorMessage, requestID string) error

	// LogStreamingRequest initiates logging for a streaming request and returns a writer for chunks.
	//
	// Parameters:
	//   - url: The request URL
	//   - method: The HTTP method
	//   - headers: The request headers
	//   - body: The request body
	//   - requestID: Optional request ID for log file naming
	//
	// Returns:
	//   - StreamingLogWriter: A writer for streaming response chunks
	//   - error: An error if logging initialization fails, nil otherwise
	LogStreamingRequest(url, method string, headers map[string][]string, body []byte, requestID string) (StreamingLogWriter, error)

	// IsEnabled returns whether request logging is currently enabled.
	//
	// Returns:
	//   - bool: True if logging is enabled, false otherwise
	IsEnabled() bool
}

// StreamingLogWriter handles real-time logging of streaming response chunks.
// It provides methods for writing streaming response data asynchronously.
type StreamingLogWriter interface {
	// WriteChunkAsync writes a response chunk asynchronously (non-blocking).
	//
	// Parameters:
	//   - chunk: The response chunk to write
	WriteChunkAsync(chunk []byte)

	// WriteStatus writes the response status and headers to the log.
	//
	// Parameters:
	//   - status: The response status code
	//   - headers: The response headers
	//
	// Returns:
	//   - error: An error if writing fails, nil otherwise
	WriteStatus(status int, headers map[string][]string) error

	// WriteAPIRequest writes the upstream API request details to the log.
	// This should be called before WriteStatus to maintain proper log ordering.
	//
	// Parameters:
	//   - apiRequest: The API request data (typically includes URL, headers, body sent upstream)
	//
	// Returns:
	//   - error: An error if writing fails, nil otherwise
	WriteAPIRequest(apiRequest []byte) error

	// WriteAPIResponse writes the upstream API response details to the log.
	// This should be called after the streaming response is complete.
	//
	// Parameters:
	//   - apiResponse: The API response data
	//
	// Returns:
	//   - error: An error if writing fails, nil otherwise
	WriteAPIResponse(apiResponse []byte) error

	// Close finalizes the log file and cleans up resources.
	//
	// Returns:
	//   - error: An error if closing fails, nil otherwise
	Close() error
}

// FileRequestLogger implements RequestLogger using file-based storage.
// It provides file-based logging functionality for HTTP requests and responses.
type FileRequestLogger struct {
	// enabled indicates whether request logging is currently enabled.
	enabled bool

	// logsDir is the directory where log files are stored.
	logsDir string
}

// NewFileRequestLogger creates a new file-based request logger.
//
// Parameters:
//   - enabled: Whether request logging should be enabled
//   - logsDir: The directory where log files should be stored (can be relative)
//   - configDir: The directory of the configuration file; when logsDir is
//     relative, it will be resolved relative to this directory
//
// Returns:
//   - *FileRequestLogger: A new file-based request logger instance
func NewFileRequestLogger(enabled bool, logsDir string, configDir string) *FileRequestLogger {
	// Resolve logsDir relative to the configuration file directory when it's not absolute.
	if !filepath.IsAbs(logsDir) {
		// If configDir is provided, resolve logsDir relative to it.
		if configDir != "" {
			logsDir = filepath.Join(configDir, logsDir)
		}
	}
	return &FileRequestLogger{
		enabled: enabled,
		logsDir: logsDir,
	}
}

// IsEnabled returns whether request logging is currently enabled.
//
// Returns:
//   - bool: True if logging is enabled, false otherwise
func (l *FileRequestLogger) IsEnabled() bool {
	return l.enabled
}

// SetEnabled updates the request logging enabled state.
// This method allows dynamic enabling/disabling of request logging.
//
// Parameters:
//   - enabled: Whether request logging should be enabled
func (l *FileRequestLogger) SetEnabled(enabled bool) {
	l.enabled = enabled
}

// LogRequest logs a complete non-streaming request/response cycle to a file.
//
// Parameters:
//   - url: The request URL
//   - method: The HTTP method
//   - requestHeaders: The request headers
//   - body: The request body
//   - statusCode: The response status code
//   - responseHeaders: The response headers
//   - response: The raw response data
//   - apiRequest: The API request data
//   - apiResponse: The API response data
//   - requestID: Optional request ID for log file naming
//
// Returns:
//   - error: An error if logging fails, nil otherwise
func (l *FileRequestLogger) LogRequest(url, method string, requestHeaders map[string][]string, body []byte, statusCode int, responseHeaders map[string][]string, response, apiRequest, apiResponse []byte, apiResponseErrors []*interfaces.ErrorMessage, requestID string) error {
	return l.logRequest(url, method, requestHeaders, body, statusCode, responseHeaders, response, apiRequest, apiResponse, apiResponseErrors, false, requestID)
}

// LogRequestWithOptions logs a request with optional forced logging behavior.
// The force flag allows writing error logs even when regular request logging is disabled.
func (l *FileRequestLogger) LogRequestWithOptions(url, method string, requestHeaders map[string][]string, body []byte, statusCode int, responseHeaders map[string][]string, response, apiRequest, apiResponse []byte, apiResponseErrors []*interfaces.ErrorMessage, force bool, requestID string) error {
	return l.logRequest(url, method, requestHeaders, body, statusCode, responseHeaders, response, apiRequest, apiResponse, apiResponseErrors, force, requestID)
}

func (l *FileRequestLogger) logRequest(url, method string, requestHeaders map[string][]string, body []byte, statusCode int, responseHeaders map[string][]string, response, apiRequest, apiResponse []byte, apiResponseErrors []*interfaces.ErrorMessage, force bool, requestID string) error {
	if !l.enabled && !force {
		return nil
	}

	// Ensure logs directory exists
	if errEnsure := l.ensureLogsDir(); errEnsure != nil {
		return fmt.Errorf("failed to create logs directory: %w", errEnsure)
	}

	// Generate filename with request ID
	filename := l.generateFilename(url, requestID)
	if force && !l.enabled {
		filename = l.generateErrorFilename(url, requestID)
	}
	filePath := filepath.Join(l.logsDir, filename)

	requestBodyPath, errTemp := l.writeRequestBodyTempFile(body)
	if errTemp != nil {
		log.WithError(errTemp).Warn("failed to create request body temp file, falling back to direct write")
	}
	if requestBodyPath != "" {
		defer func() {
			if errRemove := os.Remove(requestBodyPath); errRemove != nil {
				log.WithError(errRemove).Warn("failed to remove request body temp file")
			}
		}()
	}

	responseToWrite, decompressErr := l.decompressResponse(responseHeaders, response)
	if decompressErr != nil {
		// If decompression fails, continue with original response and annotate the log output.
		responseToWrite = response
	}

	logFile, errOpen := os.OpenFile(filePath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
	if errOpen != nil {
		return fmt.Errorf("failed to create log file: %w", errOpen)
	}

	writeErr := l.writeNonStreamingLog(
		logFile,
		url,
		method,
		requestHeaders,
		body,
		requestBodyPath,
		apiRequest,
		apiResponse,
		apiResponseErrors,
		statusCode,
		responseHeaders,
		responseToWrite,
		decompressErr,
	)
	if errClose := logFile.Close(); errClose != nil {
		log.WithError(errClose).Warn("failed to close request log file")
		if writeErr == nil {
			return errClose
		}
	}
	if writeErr != nil {
		return fmt.Errorf("failed to write log file: %w", writeErr)
	}

	if force && !l.enabled {
		if errCleanup := l.cleanupOldErrorLogs(); errCleanup != nil {
			log.WithError(errCleanup).Warn("failed to clean up old error logs")
		}
	}

	return nil
}

// LogStreamingRequest initiates logging for a streaming request.
//
// Parameters:
//   - url: The request URL
//   - method: The HTTP method
//   - headers: The request headers
//   - body: The request body
//   - requestID: Optional request ID for log file naming
//
// Returns:
//   - StreamingLogWriter: A writer for streaming response chunks
//   - error: An error if logging initialization fails, nil otherwise
func (l *FileRequestLogger) LogStreamingRequest(url, method string, headers map[string][]string, body []byte, requestID string) (StreamingLogWriter, error) {
	if !l.enabled {
		return &NoOpStreamingLogWriter{}, nil
	}

	// Ensure logs directory exists
	if err := l.ensureLogsDir(); err != nil {
		return nil, fmt.Errorf("failed to create logs directory: %w", err)
	}

	// Generate filename with request ID
	filename := l.generateFilename(url, requestID)
	filePath := filepath.Join(l.logsDir, filename)

	requestHeaders := make(map[string][]string, len(headers))
	for key, values := range headers {
		headerValues := make([]string, len(values))
		copy(headerValues, values)
		requestHeaders[key] = headerValues
	}

	requestBodyPath, errTemp := l.writeRequestBodyTempFile(body)
	if errTemp != nil {
		return nil, fmt.Errorf("failed to create request body temp file: %w", errTemp)
	}

	responseBodyFile, errCreate := os.CreateTemp(l.logsDir, "response-body-*.tmp")
	if errCreate != nil {
		_ = os.Remove(requestBodyPath)
		return nil, fmt.Errorf("failed to create response body temp file: %w", errCreate)
	}
	responseBodyPath := responseBodyFile.Name()

	// Create streaming writer
	writer := &FileStreamingLogWriter{
		logFilePath:      filePath,
		url:              url,
		method:           method,
		timestamp:        time.Now(),
		requestHeaders:   requestHeaders,
		requestBodyPath:  requestBodyPath,
		responseBodyPath: responseBodyPath,
		responseBodyFile: responseBodyFile,
		chunkChan:        make(chan []byte, 100), // Buffered channel for async writes
		closeChan:        make(chan struct{}),
		errorChan:        make(chan error, 1),
	}

	// Start async writer goroutine
	go writer.asyncWriter()

	return writer, nil
}

// generateErrorFilename creates a filename with an error prefix to differentiate forced error logs.
func (l *FileRequestLogger) generateErrorFilename(url string, requestID ...string) string {
	return fmt.Sprintf("error-%s", l.generateFilename(url, requestID...))
}

// ensureLogsDir creates the logs directory if it doesn't exist.
//
// Returns:
//   - error: An error if directory creation fails, nil otherwise
func (l *FileRequestLogger) ensureLogsDir() error {
	if _, err := os.Stat(l.logsDir); os.IsNotExist(err) {
		return os.MkdirAll(l.logsDir, 0755)
	}
	return nil
}

// generateFilename creates a sanitized filename from the URL path and current timestamp.
// Format: v1-responses-2025-12-23T195811-a1b2c3d4.log
//
// Parameters:
//   - url: The request URL
//   - requestID: Optional request ID to include in filename
//
// Returns:
//   - string: A sanitized filename for the log file
func (l *FileRequestLogger) generateFilename(url string, requestID ...string) string {
	// Extract path from URL
	path := url
	if strings.Contains(url, "?") {
		path = strings.Split(url, "?")[0]
	}

	// Remove leading slash
	if strings.HasPrefix(path, "/") {
		path = path[1:]
	}

	// Sanitize path for filename
	sanitized := l.sanitizeForFilename(path)

	// Add timestamp
	timestamp := time.Now().Format("2006-01-02T150405")

	// Use request ID if provided, otherwise use sequential ID
	var idPart string
	if len(requestID) > 0 && requestID[0] != "" {
		idPart = requestID[0]
	} else {
		id := requestLogID.Add(1)
		idPart = fmt.Sprintf("%d", id)
	}

	return fmt.Sprintf("%s-%s-%s.log", sanitized, timestamp, idPart)
}

// sanitizeForFilename replaces characters that are not safe for filenames.
//
// Parameters:
//   - path: The path to sanitize
//
// Returns:
//   - string: A sanitized filename
func (l *FileRequestLogger) sanitizeForFilename(path string) string {
	// Replace slashes with hyphens
	sanitized := strings.ReplaceAll(path, "/", "-")

	// Replace colons with hyphens
	sanitized = strings.ReplaceAll(sanitized, ":", "-")

	// Replace other problematic characters with hyphens
	reg := regexp.MustCompile(`[<>:"|?*\s]`)
	sanitized = reg.ReplaceAllString(sanitized, "-")

	// Remove multiple consecutive hyphens
	reg = regexp.MustCompile(`-+`)
	sanitized = reg.ReplaceAllString(sanitized, "-")

	// Remove leading/trailing hyphens
	sanitized = strings.Trim(sanitized, "-")

	// Handle empty result
	if sanitized == "" {
		sanitized = "root"
	}

	return sanitized
}

// cleanupOldErrorLogs keeps only the newest 10 forced error log files.
func (l *FileRequestLogger) cleanupOldErrorLogs() error {
	entries, errRead := os.ReadDir(l.logsDir)
	if errRead != nil {
		return errRead
	}

	type logFile struct {
		name    string
		modTime time.Time
	}

	var files []logFile
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}
		name := entry.Name()
		if !strings.HasPrefix(name, "error-") || !strings.HasSuffix(name, ".log") {
			continue
		}
		info, errInfo := entry.Info()
		if errInfo != nil {
			log.WithError(errInfo).Warn("failed to read error log info")
			continue
		}
		files = append(files, logFile{name: name, modTime: info.ModTime()})
	}

	if len(files) <= 10 {
		return nil
	}

	sort.Slice(files, func(i, j int) bool {
		return files[i].modTime.After(files[j].modTime)
	})

	for _, file := range files[10:] {
		if errRemove := os.Remove(filepath.Join(l.logsDir, file.name)); errRemove != nil {
			log.WithError(errRemove).Warnf("failed to remove old error log: %s", file.name)
		}
	}

	return nil
}

func (l *FileRequestLogger) writeRequestBodyTempFile(body []byte) (string, error) {
	tmpFile, errCreate := os.CreateTemp(l.logsDir, "request-body-*.tmp")
	if errCreate != nil {
		return "", errCreate
	}
	tmpPath := tmpFile.Name()

	if _, errCopy := io.Copy(tmpFile, bytes.NewReader(body)); errCopy != nil {
		_ = tmpFile.Close()
		_ = os.Remove(tmpPath)
		return "", errCopy
	}
	if errClose := tmpFile.Close(); errClose != nil {
		_ = os.Remove(tmpPath)
		return "", errClose
	}
	return tmpPath, nil
}

func (l *FileRequestLogger) writeNonStreamingLog(
	w io.Writer,
	url, method string,
	requestHeaders map[string][]string,
	requestBody []byte,
	requestBodyPath string,
	apiRequest []byte,
	apiResponse []byte,
	apiResponseErrors []*interfaces.ErrorMessage,
	statusCode int,
	responseHeaders map[string][]string,
	response []byte,
	decompressErr error,
) error {
	if errWrite := writeRequestInfoWithBody(w, url, method, requestHeaders, requestBody, requestBodyPath, time.Now()); errWrite != nil {
		return errWrite
	}
	if errWrite := writeAPISection(w, "=== API REQUEST ===\n", "=== API REQUEST", apiRequest); errWrite != nil {
		return errWrite
	}
	if errWrite := writeAPIErrorResponses(w, apiResponseErrors); errWrite != nil {
		return errWrite
	}
	if errWrite := writeAPISection(w, "=== API RESPONSE ===\n", "=== API RESPONSE", apiResponse); errWrite != nil {
		return errWrite
	}
	return writeResponseSection(w, statusCode, true, responseHeaders, bytes.NewReader(response), decompressErr, true)
}

func writeRequestInfoWithBody(
	w io.Writer,
	url, method string,
	headers map[string][]string,
	body []byte,
	bodyPath string,
	timestamp time.Time,
) error {
	if _, errWrite := io.WriteString(w, "=== REQUEST INFO ===\n"); errWrite != nil {
		return errWrite
	}
	if _, errWrite := io.WriteString(w, fmt.Sprintf("Version: %s\n", buildinfo.Version)); errWrite != nil {
		return errWrite
	}
	if _, errWrite := io.WriteString(w, fmt.Sprintf("URL: %s\n", url)); errWrite != nil {
		return errWrite
	}
	if _, errWrite := io.WriteString(w, fmt.Sprintf("Method: %s\n", method)); errWrite != nil {
		return errWrite
	}
	if _, errWrite := io.WriteString(w, fmt.Sprintf("Timestamp: %s\n", timestamp.Format(time.RFC3339Nano))); errWrite != nil {
		return errWrite
	}
	if _, errWrite := io.WriteString(w, "\n"); errWrite != nil {
		return errWrite
	}

	if _, errWrite := io.WriteString(w, "=== HEADERS ===\n"); errWrite != nil {
		return errWrite
	}
	for key, values := range headers {
		for _, value := range values {
			masked := util.MaskSensitiveHeaderValue(key, value)
			if _, errWrite := io.WriteString(w, fmt.Sprintf("%s: %s\n", key, masked)); errWrite != nil {
				return errWrite
			}
		}
	}
	if _, errWrite := io.WriteString(w, "\n"); errWrite != nil {
		return errWrite
	}

	if _, errWrite := io.WriteString(w, "=== REQUEST BODY ===\n"); errWrite != nil {
		return errWrite
	}

	if bodyPath != "" {
		bodyFile, errOpen := os.Open(bodyPath)
		if errOpen != nil {
			return errOpen
		}
		if _, errCopy := io.Copy(w, bodyFile); errCopy != nil {
			_ = bodyFile.Close()
			return errCopy
		}
		if errClose := bodyFile.Close(); errClose != nil {
			log.WithError(errClose).Warn("failed to close request body temp file")
		}
	} else if _, errWrite := w.Write(body); errWrite != nil {
		return errWrite
	}

	if _, errWrite := io.WriteString(w, "\n\n"); errWrite != nil {
		return errWrite
	}
	return nil
}

func writeAPISection(w io.Writer, sectionHeader string, sectionPrefix string, payload []byte) error {
	if len(payload) == 0 {
		return nil
	}

	if bytes.HasPrefix(payload, []byte(sectionPrefix)) {
		if _, errWrite := w.Write(payload); errWrite != nil {
			return errWrite
		}
		if !bytes.HasSuffix(payload, []byte("\n")) {
			if _, errWrite := io.WriteString(w, "\n"); errWrite != nil {
				return errWrite
			}
		}
	} else {
		if _, errWrite := io.WriteString(w, sectionHeader); errWrite != nil {
			return errWrite
		}
		if _, errWrite := w.Write(payload); errWrite != nil {
			return errWrite
		}
		if _, errWrite := io.WriteString(w, "\n"); errWrite != nil {
			return errWrite
		}
	}

	if _, errWrite := io.WriteString(w, "\n"); errWrite != nil {
		return errWrite
	}
	return nil
}

func writeAPIErrorResponses(w io.Writer, apiResponseErrors []*interfaces.ErrorMessage) error {
	for i := 0; i < len(apiResponseErrors); i++ {
		if apiResponseErrors[i] == nil {
			continue
		}
		if _, errWrite := io.WriteString(w, "=== API ERROR RESPONSE ===\n"); errWrite != nil {
			return errWrite
		}
		if _, errWrite := io.WriteString(w, fmt.Sprintf("HTTP Status: %d\n", apiResponseErrors[i].StatusCode)); errWrite != nil {
			return errWrite
		}
		if apiResponseErrors[i].Error != nil {
			if _, errWrite := io.WriteString(w, apiResponseErrors[i].Error.Error()); errWrite != nil {
				return errWrite
			}
		}
		if _, errWrite := io.WriteString(w, "\n\n"); errWrite != nil {
			return errWrite
		}
	}
	return nil
}

func writeResponseSection(w io.Writer, statusCode int, statusWritten bool, responseHeaders map[string][]string, responseReader io.Reader, decompressErr error, trailingNewline bool) error {
	if _, errWrite := io.WriteString(w, "=== RESPONSE ===\n"); errWrite != nil {
		return errWrite
	}
	if statusWritten {
		if _, errWrite := io.WriteString(w, fmt.Sprintf("Status: %d\n", statusCode)); errWrite != nil {
			return errWrite
		}
	}

	if responseHeaders != nil {
		for key, values := range responseHeaders {
			for _, value := range values {
				if _, errWrite := io.WriteString(w, fmt.Sprintf("%s: %s\n", key, value)); errWrite != nil {
					return errWrite
				}
			}
		}
	}

	if _, errWrite := io.WriteString(w, "\n"); errWrite != nil {
		return errWrite
	}

	if responseReader != nil {
		if _, errCopy := io.Copy(w, responseReader); errCopy != nil {
			return errCopy
		}
	}
	if decompressErr != nil {
		if _, errWrite := io.WriteString(w, fmt.Sprintf("\n[DECOMPRESSION ERROR: %v]", decompressErr)); errWrite != nil {
			return errWrite
		}
	}

	if trailingNewline {
		if _, errWrite := io.WriteString(w, "\n"); errWrite != nil {
			return errWrite
		}
	}
	return nil
}

// formatLogContent creates the complete log content for non-streaming requests.
//
// Parameters:
//   - url: The request URL
//   - method: The HTTP method
//   - headers: The request headers
//   - body: The request body
//   - apiRequest: The API request data
//   - apiResponse: The API response data
//   - response: The raw response data
//   - status: The response status code
//   - responseHeaders: The response headers
//
// Returns:
//   - string: The formatted log content
func (l *FileRequestLogger) formatLogContent(url, method string, headers map[string][]string, body, apiRequest, apiResponse, response []byte, status int, responseHeaders map[string][]string, apiResponseErrors []*interfaces.ErrorMessage) string {
	var content strings.Builder

	// Request info
	content.WriteString(l.formatRequestInfo(url, method, headers, body))

	if len(apiRequest) > 0 {
		if bytes.HasPrefix(apiRequest, []byte("=== API REQUEST")) {
			content.Write(apiRequest)
			if !bytes.HasSuffix(apiRequest, []byte("\n")) {
				content.WriteString("\n")
			}
		} else {
			content.WriteString("=== API REQUEST ===\n")
			content.Write(apiRequest)
			content.WriteString("\n")
		}
		content.WriteString("\n")
	}

	for i := 0; i < len(apiResponseErrors); i++ {
		content.WriteString("=== API ERROR RESPONSE ===\n")
		content.WriteString(fmt.Sprintf("HTTP Status: %d\n", apiResponseErrors[i].StatusCode))
		content.WriteString(apiResponseErrors[i].Error.Error())
		content.WriteString("\n\n")
	}

	if len(apiResponse) > 0 {
		if bytes.HasPrefix(apiResponse, []byte("=== API RESPONSE")) {
			content.Write(apiResponse)
			if !bytes.HasSuffix(apiResponse, []byte("\n")) {
				content.WriteString("\n")
			}
		} else {
			content.WriteString("=== API RESPONSE ===\n")
			content.Write(apiResponse)
			content.WriteString("\n")
		}
		content.WriteString("\n")
	}

	// Response section
	content.WriteString("=== RESPONSE ===\n")
	content.WriteString(fmt.Sprintf("Status: %d\n", status))

	if responseHeaders != nil {
		for key, values := range responseHeaders {
			for _, value := range values {
				content.WriteString(fmt.Sprintf("%s: %s\n", key, value))
			}
		}
	}

	content.WriteString("\n")
	content.Write(response)
	content.WriteString("\n")

	return content.String()
}

// decompressResponse decompresses response data based on Content-Encoding header.
//
// Parameters:
//   - responseHeaders: The response headers
//   - response: The response data to decompress
//
// Returns:
//   - []byte: The decompressed response data
//   - error: An error if decompression fails, nil otherwise
func (l *FileRequestLogger) decompressResponse(responseHeaders map[string][]string, response []byte) ([]byte, error) {
	if responseHeaders == nil || len(response) == 0 {
		return response, nil
	}

	// Check Content-Encoding header
	var contentEncoding string
	for key, values := range responseHeaders {
		if strings.ToLower(key) == "content-encoding" && len(values) > 0 {
			contentEncoding = strings.ToLower(values[0])
			break
		}
	}

	switch contentEncoding {
	case "gzip":
		return l.decompressGzip(response)
	case "deflate":
		return l.decompressDeflate(response)
	case "br":
		return l.decompressBrotli(response)
	case "zstd":
		return l.decompressZstd(response)
	default:
		// No compression or unsupported compression
		return response, nil
	}
}

// decompressGzip decompresses gzip-encoded data.
//
// Parameters:
//   - data: The gzip-encoded data to decompress
//
// Returns:
//   - []byte: The decompressed data
//   - error: An error if decompression fails, nil otherwise
func (l *FileRequestLogger) decompressGzip(data []byte) ([]byte, error) {
	reader, err := gzip.NewReader(bytes.NewReader(data))
	if err != nil {
		return nil, fmt.Errorf("failed to create gzip reader: %w", err)
	}
	defer func() {
		if errClose := reader.Close(); errClose != nil {
			log.WithError(errClose).Warn("failed to close gzip reader in request logger")
		}
	}()

	decompressed, err := io.ReadAll(reader)
	if err != nil {
		return nil, fmt.Errorf("failed to decompress gzip data: %w", err)
	}

	return decompressed, nil
}

// decompressDeflate decompresses deflate-encoded data.
//
// Parameters:
//   - data: The deflate-encoded data to decompress
//
// Returns:
//   - []byte: The decompressed data
//   - error: An error if decompression fails, nil otherwise
func (l *FileRequestLogger) decompressDeflate(data []byte) ([]byte, error) {
	reader := flate.NewReader(bytes.NewReader(data))
	defer func() {
		if errClose := reader.Close(); errClose != nil {
			log.WithError(errClose).Warn("failed to close deflate reader in request logger")
		}
	}()

	decompressed, err := io.ReadAll(reader)
	if err != nil {
		return nil, fmt.Errorf("failed to decompress deflate data: %w", err)
	}

	return decompressed, nil
}

// decompressBrotli decompresses brotli-encoded data.
//
// Parameters:
//   - data: The brotli-encoded data to decompress
//
// Returns:
//   - []byte: The decompressed data
//   - error: An error if decompression fails, nil otherwise
func (l *FileRequestLogger) decompressBrotli(data []byte) ([]byte, error) {
	reader := brotli.NewReader(bytes.NewReader(data))

	decompressed, err := io.ReadAll(reader)
	if err != nil {
		return nil, fmt.Errorf("failed to decompress brotli data: %w", err)
	}

	return decompressed, nil
}

// decompressZstd decompresses zstd-encoded data.
//
// Parameters:
//   - data: The zstd-encoded data to decompress
//
// Returns:
//   - []byte: The decompressed data
//   - error: An error if decompression fails, nil otherwise
func (l *FileRequestLogger) decompressZstd(data []byte) ([]byte, error) {
	decoder, err := zstd.NewReader(bytes.NewReader(data))
	if err != nil {
		return nil, fmt.Errorf("failed to create zstd reader: %w", err)
	}
	defer decoder.Close()

	decompressed, err := io.ReadAll(decoder)
	if err != nil {
		return nil, fmt.Errorf("failed to decompress zstd data: %w", err)
	}

	return decompressed, nil
}

// formatRequestInfo creates the request information section of the log.
//
// Parameters:
//   - url: The request URL
//   - method: The HTTP method
//   - headers: The request headers
//   - body: The request body
//
// Returns:
//   - string: The formatted request information
func (l *FileRequestLogger) formatRequestInfo(url, method string, headers map[string][]string, body []byte) string {
	var content strings.Builder

	content.WriteString("=== REQUEST INFO ===\n")
	content.WriteString(fmt.Sprintf("Version: %s\n", buildinfo.Version))
	content.WriteString(fmt.Sprintf("URL: %s\n", url))
	content.WriteString(fmt.Sprintf("Method: %s\n", method))
	content.WriteString(fmt.Sprintf("Timestamp: %s\n", time.Now().Format(time.RFC3339Nano)))
	content.WriteString("\n")

	content.WriteString("=== HEADERS ===\n")
	for key, values := range headers {
		for _, value := range values {
			masked := util.MaskSensitiveHeaderValue(key, value)
			content.WriteString(fmt.Sprintf("%s: %s\n", key, masked))
		}
	}
	content.WriteString("\n")

	content.WriteString("=== REQUEST BODY ===\n")
	content.Write(body)
	content.WriteString("\n\n")

	return content.String()
}

// FileStreamingLogWriter implements StreamingLogWriter for file-based streaming logs.
// It spools streaming response chunks to a temporary file to avoid retaining large responses in memory.
// The final log file is assembled when Close is called.
type FileStreamingLogWriter struct {
	// logFilePath is the final log file path.
	logFilePath string

	// url is the request URL (masked upstream in middleware).
	url string

	// method is the HTTP method.
	method string

	// timestamp is captured when the streaming log is initialized.
	timestamp time.Time

	// requestHeaders stores the request headers.
	requestHeaders map[string][]string

	// requestBodyPath is a temporary file path holding the request body.
	requestBodyPath string

	// responseBodyPath is a temporary file path holding the streaming response body.
	responseBodyPath string

	// responseBodyFile is the temp file where chunks are appended by the async writer.
	responseBodyFile *os.File

	// chunkChan is a channel for receiving response chunks to spool.
	chunkChan chan []byte

	// closeChan is a channel for signaling when the writer is closed.
	closeChan chan struct{}

	// errorChan is a channel for reporting errors during writing.
	errorChan chan error

	// responseStatus stores the HTTP status code.
	responseStatus int

	// statusWritten indicates whether a non-zero status was recorded.
	statusWritten bool

	// responseHeaders stores the response headers.
	responseHeaders map[string][]string

	// apiRequest stores the upstream API request data.
	apiRequest []byte

	// apiResponse stores the upstream API response data.
	apiResponse []byte
}

// WriteChunkAsync writes a response chunk asynchronously (non-blocking).
//
// Parameters:
//   - chunk: The response chunk to write
func (w *FileStreamingLogWriter) WriteChunkAsync(chunk []byte) {
	if w.chunkChan == nil {
		return
	}

	// Make a copy of the chunk to avoid data races
	chunkCopy := make([]byte, len(chunk))
	copy(chunkCopy, chunk)

	// Non-blocking send
	select {
	case w.chunkChan <- chunkCopy:
	default:
		// Channel is full, skip this chunk to avoid blocking
	}
}

// WriteStatus buffers the response status and headers for later writing.
//
// Parameters:
//   - status: The response status code
//   - headers: The response headers
//
// Returns:
//   - error: Always returns nil (buffering cannot fail)
func (w *FileStreamingLogWriter) WriteStatus(status int, headers map[string][]string) error {
	if status == 0 {
		return nil
	}

	w.responseStatus = status
	if headers != nil {
		w.responseHeaders = make(map[string][]string, len(headers))
		for key, values := range headers {
			headerValues := make([]string, len(values))
			copy(headerValues, values)
			w.responseHeaders[key] = headerValues
		}
	}
	w.statusWritten = true
	return nil
}

// WriteAPIRequest buffers the upstream API request details for later writing.
//
// Parameters:
//   - apiRequest: The API request data (typically includes URL, headers, body sent upstream)
//
// Returns:
//   - error: Always returns nil (buffering cannot fail)
func (w *FileStreamingLogWriter) WriteAPIRequest(apiRequest []byte) error {
	if len(apiRequest) == 0 {
		return nil
	}
	w.apiRequest = bytes.Clone(apiRequest)
	return nil
}

// WriteAPIResponse buffers the upstream API response details for later writing.
//
// Parameters:
//   - apiResponse: The API response data
//
// Returns:
//   - error: Always returns nil (buffering cannot fail)
func (w *FileStreamingLogWriter) WriteAPIResponse(apiResponse []byte) error {
	if len(apiResponse) == 0 {
		return nil
	}
	w.apiResponse = bytes.Clone(apiResponse)
	return nil
}

// Close finalizes the log file and cleans up resources.
// It writes all buffered data to the file in the correct order:
// API REQUEST -> API RESPONSE -> RESPONSE (status, headers, body chunks)
//
// Returns:
//   - error: An error if closing fails, nil otherwise
func (w *FileStreamingLogWriter) Close() error {
	if w.chunkChan != nil {
		close(w.chunkChan)
	}

	// Wait for async writer to finish spooling chunks
	if w.closeChan != nil {
		<-w.closeChan
		w.chunkChan = nil
	}

	select {
	case errWrite := <-w.errorChan:
		w.cleanupTempFiles()
		return errWrite
	default:
	}

	if w.logFilePath == "" {
		w.cleanupTempFiles()
		return nil
	}

	logFile, errOpen := os.OpenFile(w.logFilePath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
	if errOpen != nil {
		w.cleanupTempFiles()
		return fmt.Errorf("failed to create log file: %w", errOpen)
	}

	writeErr := w.writeFinalLog(logFile)
	if errClose := logFile.Close(); errClose != nil {
		log.WithError(errClose).Warn("failed to close request log file")
		if writeErr == nil {
			writeErr = errClose
		}
	}

	w.cleanupTempFiles()
	return writeErr
}

// asyncWriter runs in a goroutine to buffer chunks from the channel.
// It continuously reads chunks from the channel and appends them to a temp file for later assembly.
func (w *FileStreamingLogWriter) asyncWriter() {
	defer close(w.closeChan)

	for chunk := range w.chunkChan {
		if w.responseBodyFile == nil {
			continue
		}
		if _, errWrite := w.responseBodyFile.Write(chunk); errWrite != nil {
			select {
			case w.errorChan <- errWrite:
			default:
			}
			if errClose := w.responseBodyFile.Close(); errClose != nil {
				select {
				case w.errorChan <- errClose:
				default:
				}
			}
			w.responseBodyFile = nil
		}
	}

	if w.responseBodyFile == nil {
		return
	}
	if errClose := w.responseBodyFile.Close(); errClose != nil {
		select {
		case w.errorChan <- errClose:
		default:
		}
	}
	w.responseBodyFile = nil
}

func (w *FileStreamingLogWriter) writeFinalLog(logFile *os.File) error {
	if errWrite := writeRequestInfoWithBody(logFile, w.url, w.method, w.requestHeaders, nil, w.requestBodyPath, w.timestamp); errWrite != nil {
		return errWrite
	}
	if errWrite := writeAPISection(logFile, "=== API REQUEST ===\n", "=== API REQUEST", w.apiRequest); errWrite != nil {
		return errWrite
	}
	if errWrite := writeAPISection(logFile, "=== API RESPONSE ===\n", "=== API RESPONSE", w.apiResponse); errWrite != nil {
		return errWrite
	}

	responseBodyFile, errOpen := os.Open(w.responseBodyPath)
	if errOpen != nil {
		return errOpen
	}
	defer func() {
		if errClose := responseBodyFile.Close(); errClose != nil {
			log.WithError(errClose).Warn("failed to close response body temp file")
		}
	}()

	return writeResponseSection(logFile, w.responseStatus, w.statusWritten, w.responseHeaders, responseBodyFile, nil, false)
}

func (w *FileStreamingLogWriter) cleanupTempFiles() {
	if w.requestBodyPath != "" {
		if errRemove := os.Remove(w.requestBodyPath); errRemove != nil {
			log.WithError(errRemove).Warn("failed to remove request body temp file")
		}
		w.requestBodyPath = ""
	}

	if w.responseBodyPath != "" {
		if errRemove := os.Remove(w.responseBodyPath); errRemove != nil {
			log.WithError(errRemove).Warn("failed to remove response body temp file")
		}
		w.responseBodyPath = ""
	}
}

// NoOpStreamingLogWriter is a no-operation implementation for when logging is disabled.
// It implements the StreamingLogWriter interface but performs no actual logging operations.
type NoOpStreamingLogWriter struct{}

// WriteChunkAsync is a no-op implementation that does nothing.
//
// Parameters:
//   - chunk: The response chunk (ignored)
func (w *NoOpStreamingLogWriter) WriteChunkAsync(_ []byte) {}

// WriteStatus is a no-op implementation that does nothing and always returns nil.
//
// Parameters:
//   - status: The response status code (ignored)
//   - headers: The response headers (ignored)
//
// Returns:
//   - error: Always returns nil
func (w *NoOpStreamingLogWriter) WriteStatus(_ int, _ map[string][]string) error {
	return nil
}

// WriteAPIRequest is a no-op implementation that does nothing and always returns nil.
//
// Parameters:
//   - apiRequest: The API request data (ignored)
//
// Returns:
//   - error: Always returns nil
func (w *NoOpStreamingLogWriter) WriteAPIRequest(_ []byte) error {
	return nil
}

// WriteAPIResponse is a no-op implementation that does nothing and always returns nil.
//
// Parameters:
//   - apiResponse: The API response data (ignored)
//
// Returns:
//   - error: Always returns nil
func (w *NoOpStreamingLogWriter) WriteAPIResponse(_ []byte) error {
	return nil
}

// Close is a no-op implementation that does nothing and always returns nil.
//
// Returns:
//   - error: Always returns nil
func (w *NoOpStreamingLogWriter) Close() error { return nil }