package backend

import (
	"os"
	"os/exec"
	"path/filepath"
	"encoding/json"
	"errors"
	"git.noctra.dev/noctra/servtex/globals"
	"time"
)

func getLocalTime() time.Time {
	timezone, _ := time.LoadLocation(globals.AppConfig.Timezone)
	return time.Now().In(timezone)
}

func getLocalTimePretty() string {
	return getLocalTime().Format("02.01.2006 15:04")
}

func LogLine(message string) {
	logline := "\n" + getLocalTime().Format(time.RFC3339) + " - " + message
	globals.LogFile.WriteString(logline)
}

// Helper for configReader() that does the actual reading
// Also validates the populated fields
func configReaderParse(filePath string, configOptionStorage *globals.Config) error {
	jsonData, err := os.ReadFile(filePath)
	if err == nil {
		err = json.Unmarshal(jsonData, &configOptionStorage)
		if err != nil { 
			return errors.New("Config file could not be read")
		}
	} else {
		return errors.New("Config file does not exist")
	}

	return configValidator(*configOptionStorage)
}

func configValidator(config globals.Config) error {
	return nil
}

// Reads config file and stores the options in configOptionStorage
// Tries executable/path/configFileName
//	 %LOCALAPPDATA%\servtex\configFileName
//	 ~/.config/servtex/configFileName
func ConfigReader(configFileName string, configOptionStorage *globals.Config) error {
	exePath, err := os.Executable()
	if err == nil {
		path := filepath.Join(filepath.Dir(exePath), configFileName)
		err = configReaderParse(path, configOptionStorage)
		if err == nil { return nil }
	}

	localappdata := os.Getenv("LOCALAPPDATA")
	if localappdata != "" {
		path := filepath.Join(localappdata, "servtex", configFileName)
		err = configReaderParse(path, configOptionStorage)
		if err == nil { return nil }
	}

	path := filepath.Join("~", ".config", "servtex", configFileName)
	err = configReaderParse(path, configOptionStorage)
	if err == nil { return nil }

	return err 
}

// Watches a specified directory and calls a function on change
// Optionally, a minimum time to wait for consecutive changes can be specified
func ChangeWatch(path string, callOnChange func()) {
	LogLine("File change noticed")
}

// Intended to be run as goroutine
func LatexCompile(config globals.Config, execution *globals.LatexExecution) error {
	if !execution.ExecutionLock.TryLock() {
		LogLine("LaTeX execution already underway")
		return errors.New("Execution already in progress")
	}
	LogLine("LaTeX execution started")
	execution.ExecutionState = "Started"

	var latexCommand *exec.Cmd
	switch config.LatexEngine {
		case "lualatex":
			latexCommand = exec.Command(
				"lualatex", 
				"-output-directory=" + config.LatexOutputPath, 
				"-jobname=servtex", 
				config.LatexSourceFilePath,
			)
		default:
			execution.ExecutionState = "Unknown Latex Engine"
			execution.Output = []byte{}
			execution.Timestamp = getLocalTimePretty()
			execution.ExecutionLock.Unlock()
			return errors.New("Unknown Latex Engine")
	}

	execution.ExecutionState = "Running"
	stdout, err := latexCommand.Output()
	if err != nil { 
		execution.ExecutionState = "Failed"
		return err 
	}

	execution.Output = stdout
	execution.Timestamp = getLocalTimePretty()
	execution.ExecutionState = "Done"
	execution.ExecutionLock.Unlock()
	return nil
}