package output

import (
	"io"
	"log/slog"
	"os"

	"edp.buildth.ing/DevFW-CICD/forgejo-runner-resource-collector/internal/metrics"
)

// LogFormat specifies the log output format
type LogFormat string

const (
	LogFormatJSON LogFormat = "json"
	LogFormatText LogFormat = "text"
)

// LoggerWriter outputs metrics using structured logging
type LoggerWriter struct {
	logger *slog.Logger
	level  slog.Level
}

// LoggerConfig holds configuration for the logger
type LoggerConfig struct {
	Output io.Writer
	Format LogFormat
	Level  slog.Level
}

// NewLoggerWriter creates a new logger-based writer
func NewLoggerWriter(cfg LoggerConfig) *LoggerWriter {
	if cfg.Output == nil {
		cfg.Output = os.Stdout
	}

	var handler slog.Handler
	opts := &slog.HandlerOptions{
		Level: cfg.Level,
	}

	switch cfg.Format {
	case LogFormatText:
		handler = slog.NewTextHandler(cfg.Output, opts)
	default:
		handler = slog.NewJSONHandler(cfg.Output, opts)
	}

	return &LoggerWriter{
		logger: slog.New(handler),
		level:  cfg.Level,
	}
}

// topCPUEntry is a lightweight struct for JSON serialization of top CPU processes
type topCPUEntry struct {
	PID        int     `json:"pid"`
	Name       string  `json:"name"`
	CPUPercent float64 `json:"cpu_percent"`
}

// topMemEntry is a lightweight struct for JSON serialization of top memory processes
type topMemEntry struct {
	PID      int    `json:"pid"`
	Name     string `json:"name"`
	RSSBytes uint64 `json:"rss_bytes"`
}

// Write outputs the metrics using structured logging
func (w *LoggerWriter) Write(m *metrics.SystemMetrics) error {
	// Build top CPU process entries
	topCPU := make([]topCPUEntry, 0, len(m.TopCPU))
	for _, p := range m.TopCPU {
		topCPU = append(topCPU, topCPUEntry{
			PID:        p.PID,
			Name:       p.Name,
			CPUPercent: p.CPUPercent,
		})
	}

	// Build top memory process entries
	topMem := make([]topMemEntry, 0, len(m.TopMemory))
	for _, p := range m.TopMemory {
		topMem = append(topMem, topMemEntry{
			PID:      p.PID,
			Name:     p.Name,
			RSSBytes: p.MemRSS,
		})
	}

	w.logger.Info("metrics_collected",
		slog.Time("collection_time", m.Timestamp),
		slog.Int("total_processes", m.TotalProcesses),
		slog.Group("cpu",
			slog.Float64("total_percent", m.CPU.TotalPercent),
			slog.Float64("user_percent", m.CPU.UserPercent),
			slog.Float64("system_percent", m.CPU.SystemPercent),
			slog.Float64("idle_percent", m.CPU.IdlePercent),
			slog.Float64("iowait_percent", m.CPU.IOWaitPercent),
		),
		slog.Group("memory",
			slog.Uint64("total_bytes", m.Memory.TotalBytes),
			slog.Uint64("used_bytes", m.Memory.UsedBytes),
			slog.Uint64("free_bytes", m.Memory.FreeBytes),
			slog.Uint64("available_bytes", m.Memory.AvailableBytes),
			slog.Float64("used_percent", m.Memory.UsedPercent),
			slog.Uint64("total_rss_bytes", m.Memory.TotalRSSBytes),
			slog.Float64("rss_percent", m.Memory.RSSPercent),
		),
		slog.Any("top_cpu", topCPU),
		slog.Any("top_memory", topMem),
	)

	return nil
}

// Close is a no-op for the logger writer
func (w *LoggerWriter) Close() error {
	return nil
}

// ParseLogLevel parses a log level string
func ParseLogLevel(level string) slog.Level {
	switch level {
	case "debug":
		return slog.LevelDebug
	case "warn", "warning":
		return slog.LevelWarn
	case "error":
		return slog.LevelError
	default:
		return slog.LevelInfo
	}
}

// ParseLogFormat parses a log format string
func ParseLogFormat(format string) LogFormat {
	switch format {
	case "text":
		return LogFormatText
	default:
		return LogFormatJSON
	}
}