/*
|--------------------------------------------------------------------------
| Manifest
|--------------------------------------------------------------------------
|
| Name:
|   - Log
|
| Purpose:
|   - Provide framework-level structured plaintext logging with
|     deterministic timestamping and persistent platform-aware storage.
|
| Guideline:
|   - Use for framework and software logging.
|   - Writes append-only UTF-8 log entries.
|   - Preserves existing log content.
|   - Uses application metadata to determine storage location.
|   - Does not implement rotation, retention, archival, or compression.
|
| Example:
|   - ObrimLog("SERVICE/FEATURE", "Operation completed.")
|   - ObrimLog("HELPER/LOG", "Log initialized.")
|
|--------------------------------------------------------------------------
*/

/*
|--------------------------------------------------------------------------
| Credit
|--------------------------------------------------------------------------
|
| Contributor:
|   - Rajon Ahmed
|   - Scionite
|
|--------------------------------------------------------------------------
*/

package log

import (
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"time"

	"go/module/essential/visible/service/helper/retriever"
)

// ObrimLog writes a structured log entry.
func ObrimLog(label string, message string) {
	applicationName := obrimLogApplicationResolve()

	timestamp := obrimLogTimestampGenerate()

	entry := obrimLogEntryBuild(
		timestamp,
		label,
		message,
	)

	logDirectory := obrimLogDirectoryResolve(applicationName)

	logFile := obrimLogFileResolve(
		logDirectory,
		applicationName,
	)

	if !obrimLogFileEnsure(logDirectory, logFile) {
		return
	}

	obrimLogWrite(logFile, entry)
}

// obrimLogTimestampGenerate generates deterministic timestamps.
func obrimLogTimestampGenerate() string {
	return time.Now().UTC().Format(time.RFC3339)
}

// obrimLogEntryBuild constructs formatted log entries.
func obrimLogEntryBuild(
	timestamp string,
	label string,
	message string,
) string {
	return fmt.Sprintf(
		"[%s] [%s] %s\n",
		timestamp,
		label,
		message,
	)
}

// obrimLogApplicationResolve resolves the application name.
func obrimLogApplicationResolve() string {
	value := retriever.ObrimRetriever(
		"json",
		map[string]any{
			"resource": "application/metadata",
			"path":     "application.lower",
		},
	)

	name := strings.TrimSpace(fmt.Sprintf("%v", value))

	if name == "" {
		return "application"
	}

	return name
}

// obrimLogDirectoryResolve resolves platform-specific log directory paths.
func obrimLogDirectoryResolve(applicationName string) string {
	switch runtime.GOOS {
	case "windows":
		return obrimLogDirectoryResolveWindows(applicationName)

	case "darwin":
		return obrimLogDirectoryResolveMacOS(applicationName)

	default:
		return obrimLogDirectoryResolveLinux(applicationName)
	}
}

// obrimLogDirectoryResolveLinux resolves Linux log directory paths.
func obrimLogDirectoryResolveLinux(applicationName string) string {
	xdgStateHome := strings.TrimSpace(os.Getenv("XDG_STATE_HOME"))

	if xdgStateHome != "" {
		return filepath.Join(
			xdgStateHome,
			"."+applicationName,
			"logs",
		)
	}

	homeDirectory, errorValue := os.UserHomeDir()

	if errorValue != nil {
		return filepath.Join(
			".",
			"."+applicationName,
			"logs",
		)
	}

	return filepath.Join(
		homeDirectory,
		".local",
		"state",
		"."+applicationName,
		"logs",
	)
}

// obrimLogDirectoryResolveWindows resolves Windows log directory paths.
func obrimLogDirectoryResolveWindows(applicationName string) string {
	localApplicationData := strings.TrimSpace(
		os.Getenv("LOCALAPPDATA"),
	)

	if localApplicationData == "" {
		homeDirectory, errorValue := os.UserHomeDir()

		if errorValue == nil {
			localApplicationData = homeDirectory
		}
	}

	return filepath.Join(
		localApplicationData,
		applicationName,
		"Logs",
	)
}

// obrimLogDirectoryResolveMacOS resolves macOS log directory paths.
func obrimLogDirectoryResolveMacOS(applicationName string) string {
	homeDirectory, errorValue := os.UserHomeDir()

	if errorValue != nil {
		return filepath.Join(
			".",
			"."+applicationName,
		)
	}

	return filepath.Join(
		homeDirectory,
		"Library",
		"Logs",
		"."+applicationName,
	)
}

// obrimLogFileResolve resolves platform-specific log file paths.
func obrimLogFileResolve(
	logDirectory string,
	applicationName string,
) string {
	return filepath.Join(
		logDirectory,
		applicationName+".log",
	)
}

// obrimLogFileEnsure creates and verifies required log directories and files.
func obrimLogFileEnsure(
	logDirectory string,
	logFile string,
) bool {
	errorValue := os.MkdirAll(
		logDirectory,
		0755,
	)

	if errorValue != nil {
		return false
	}

	fileHandle, errorValue := os.OpenFile(
		logFile,
		os.O_CREATE,
		0644,
	)

	if errorValue != nil {
		return false
	}

	_ = fileHandle.Close()

	return true
}

// obrimLogWrite persists log entries to the filesystem.
func obrimLogWrite(
	logFile string,
	entry string,
) {
	fileHandle, errorValue := os.OpenFile(
		logFile,
		os.O_CREATE|os.O_WRONLY|os.O_APPEND,
		0644,
	)

	if errorValue != nil {
		return
	}

	defer fileHandle.Close()

	_, _ = fileHandle.WriteString(entry)
}