code

src/parser.go

@@ -0,0 +1,130 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+type State struct {
+	Offset		int64 	`json:"offset"`
+}
+
+func starter() {
+
+	destinationDirectory := flag.String("destDir", "", "Destination Directory")
+	flag.StringVar(destinationDirectory, "d", "", "Destination Directory (shorthand)")
+	source := flag.String("source", "", "Source Log File")
+	flag.StringVar(source, "s", "", "Source Log File (shorthand)")
+
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s --destDir <dir> --source <file>\n", os.Args[0])
+		flag.PrintDefaults()
+	}
+
+	flag.Parse()
+
+	if *destinationDirectory == "" || *source == "" {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	checkParameters(*destinationDirectory, *source)
+
+}
+
+/*
+ * TODO: This function does not check read/write permissions yet
+ */
+func checkParameters(destinationDirectory string, source string) {
+
+
+	if _, err := os.Stat(source); os.IsNotExist(err) {
+		fmt.Fprintf(os.Stderr, "Error: source file does not exist: %s\n", source)
+		os.Exit(1)
+	} else if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: failed reading source file: %s with error: %s\n", source, err)
+		os.Exit(1)
+	}
+
+	if _, err := os.Stat(destinationDirectory); os.IsNotExist(err){
+		err = os.MkdirAll(destinationDirectory, 0755)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Error: failed creating directory file: %s with error: %s\n", source, err)
+			os.Exit(1)
+		}
+	} else if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: failed reading directory file: %s with error: %s\nDid not try to create.", source, err)
+		os.Exit(1)
+	}
+
+	stateFile, err := initState(destinationDirectory)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error: failed initialising state file: %s\n", err)
+		os.Exit(1)
+	}
+
+	parseFile(stateFile, source, destinationDirectory)
+}
+
+func initState(destinationDirectory string) (stateFilePath string, err error) {
+
+	stateFile := filepath.Join(destinationDirectory, "state.json")
+
+	if _, err := os.Stat(stateFile); err == nil {
+		return stateFile, nil
+	} else if os.IsNotExist(err) {
+		fmt.Println("No state file found, creating...")
+	}
+
+	state := State{
+		Offset: 0,
+	}
+	data, err := json.MarshalIndent(state, "", "  ")
+	if err != nil {
+		return "", err
+	}
+
+	err = os.WriteFile(stateFile, data, 0644)
+	if err != nil {
+		return "", err
+	}
+
+	fmt.Printf("State file initialised: %s\n", stateFile)
+	return stateFile, nil
+}
+
+func checkState(stateFile string)  State {
+
+	data, err := os.ReadFile(stateFile)
+	if err != nil {
+		fmt.Printf("Error opening file: %v", err)
+		return State{}
+	}
+
+	var state State
+
+	err = json.Unmarshal(data, &state)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error reading state file: %s", err)
+		return State{}
+	}
+	return state
+}
+
+func updateState(stateFile string, newState State) error {
+
+	data, err := json.MarshalIndent(newState, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	err = os.WriteFile(stateFile, data, 0644)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}