/*
Copyright © 2026 Craig Williams <craig@avsdev.uk>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package logging

import (
	"log/slog"
	"os"
	"reflect"
	"unsafe"

	"github.com/lmittmann/tint"
)

// ---------- Standard log handling (terminal or file based) ----------

var logLevel slog.LevelVar
var fileLogger *os.File

// Set the logging to a particular level, quietly
func SetLevel(level slog.Level) {
	logLevel.Set(level)
}

// Enable debug level logging
func EnableDebug() {
	if logLevel.Level() > slog.LevelDebug {
		logLevel.Set(slog.LevelDebug)
		slog.Debug("Debug logging enabled")
	}
}

func LogToFile(logfile string) error {
	if fileLogger != nil {
		(*fileLogger).Close()
	}

	// Open the log file
	fileLogger, err := os.OpenFile(logfile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
	if err != nil {
		return err
	}

	opts := &slog.HandlerOptions{
		Level: &logLevel,
	}
	handler := slog.NewJSONHandler(fileLogger, opts)
	logger := slog.New(handler)
	slog.SetDefault(logger)

	return nil
}

func Shutdown() error {
	var err error = nil
	if fileLogger != nil {
		err = (*fileLogger).Close()
		fileLogger = nil
	}
	return err
}

func LogToTerminal() {
	opts := &tint.Options{
		Level:      &logLevel,
		TimeFormat: "*",
	}
	handler := tint.NewTextHandler(os.Stdout, opts)
	logger := slog.New(handler)
	slog.SetDefault(logger)
}

func IsJSONHandler(h slog.Handler) bool {
	val := reflect.ValueOf(h)

	// Ensure we are working with a pointer to a struct (*JSONHandler or *TextHandler or derived)
	if val.Kind() != reflect.Pointer || val.Elem().Kind() != reflect.Struct {
		return false
	}

	// Both JSONHandler and TextHandler wrap an unexported field named 'commonHandler'
	commonHandlerField := val.Elem().FieldByName("commonHandler")
	if !commonHandlerField.IsValid() {
		return false
	}

	// Get the underlying *commonHandler struct pointer
	// commonHandlerField is unexported, so we must use unsafe to bypass Go's safety checks
	ptr := reflect.NewAt(
		commonHandlerField.Type().Elem(),
		unsafe.Pointer(commonHandlerField.Pointer()),
	)

	// Find the unexported 'json' boolean field inside commonHandler
	jsonField := ptr.Elem().FieldByName("json")
	if !jsonField.IsValid() {
		return false
	}

	// Read the boolean value using unsafe
	return *(*bool)(unsafe.Pointer(jsonField.UnsafeAddr()))
}

func IsFileLogger() bool {
	return fileLogger != nil
}

func IsDebugEnabled() bool {
	return logLevel.Level() <= slog.LevelDebug
}