package main

import (
	"errors"
	"flag"
	"fmt"
	"io"
	"os"
	"strings"
	"unicode/utf8"

	"github.com/therootcompany/golib/io/transform/gsheet2csv"
)

const (
	fileSeparator   = "\x1c"
	groupSeparator  = "\x1d"
	recordSeparator = "\x1e"
	unitSeparator   = "\x1f"
)

func main() {
	var commentArg string
	format := "CSV"
	delim := ','
	if strings.Contains(os.Args[0], "tsv") {
		delim = '\t'
		format = "TSV"
	}

	// Parse command-line flags
	flag.StringVar(&commentArg, "comment", "#", "treat lines beginning with this rune as comments")
	outputFile := flag.String("o", "", "Output "+format+" file (default: stdout)")
	delimString := flag.String("d", string(delim), "field delimiter to use for output file ('\\t' for tab, '^_' for Unit Separator, etc)")
	useCRLF := flag.Bool("crlf", false, "use CRLF (\\r\\n) as record separator")
	urlOnly := flag.Bool("print-url", false, "don't download, just print the Google Sheet URL")
	parseOnly := flag.Bool("print-ids", false, "don't download, just print the Doc ID and Sheet ID (gid)")
	rawOnly := flag.Bool("raw", false, "don't parse, just download")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: %s [flags] <google-sheet-url-or-file-path>\n", os.Args[0])
		fmt.Fprintf(os.Stderr, "Converts a Google Sheet to %s format.\n\n", format)
		fmt.Fprintf(os.Stderr, "Flags:\n")
		flag.PrintDefaults()
		fmt.Fprintf(os.Stderr, "\nExample:\n")
		fmt.Fprintf(os.Stderr, "  %s -o output.tsv 'https://docs.google.com/spreadsheets/d/1KdNsc63pk0QRerWDPcIL9cMnGQlG-9Ue9Jlf0PAAA34/edit?gid=559037238#gid=559037238'\n", os.Args[0])
		fmt.Fprintf(os.Stderr, "  %s -o output.tsv 'file://gsheet.csv'\n", os.Args[0])
		fmt.Fprintf(os.Stderr, "  %s -o output.tsv './gsheet.csv'\n", os.Args[0])
	}
	flag.Parse()

	// Check for URL argument
	if len(flag.Args()) != 1 {
		fmt.Fprintf(os.Stderr, "Error: exactly one Google Sheet URL is required\n")
		flag.Usage()
		os.Exit(1)
	}
	url := flag.Args()[0]

	// Prepare output writer
	var out *os.File
	if *outputFile != "" {
		var err error
		out, err = os.Create(*outputFile)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Error creating output file: %v\n", err)
			os.Exit(1)
		}
		defer func() { _ = out.Close() }()
	} else {
		out = os.Stdout
	}

	switch *delimString {
	case "^_", "\\x1f":
		*delimString = unitSeparator
	case "^^", "\\x1e":
		*delimString = recordSeparator
	case "^]", "\\x1d":
		*delimString = groupSeparator
	case "^\\", "\\x1c":
		*delimString = fileSeparator
	case "^L", "\\f":
		*delimString = "\f"
	case "^K", "\\v":
		*delimString = "\v"
	case "^I", "\\t":
		*delimString = "\t"
	}
	delim, _ = utf8.DecodeRuneInString(*delimString)

	var rc io.ReadCloser
	if strings.HasPrefix(url, "https://") || strings.HasPrefix(url, "http://") {
		docid, gid := gsheet2csv.ParseIDs(url)
		if *parseOnly {
			fmt.Printf("docid=%s\ngid=%s\n", docid, gid)
		} else {
			fmt.Fprintf(os.Stderr, "docid=%s\ngid=%s\n", docid, gid)
		}

		sheetURL := gsheet2csv.ToCSVURL(docid, gid)
		if *urlOnly {
			fmt.Printf("%s\n", sheetURL)
		} else {
			fmt.Fprintf(os.Stderr, "downloading %s\n", sheetURL)
		}

		if !*urlOnly {
			resp, err := gsheet2csv.GetSheet(docid, gid)
			if err != nil {
				fmt.Fprintf(os.Stderr, "Error getting url: %v\n", err)
				os.Exit(1)
			}
			defer func() { _ = resp.Body.Close() }()
			rc = resp.Body
		}
	} else {
		url = strings.TrimPrefix(url, "file://")
		fmt.Fprintf(os.Stderr, "opening %s\n", url)
		f, err := os.Open(url)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Error opening file: %v\n", err)
			os.Exit(1)
		}
		rc = f
	}

	if out == os.Stdout {
		fmt.Fprintf(os.Stderr, "\n")
	}

	if *urlOnly || *parseOnly {
		os.Exit(0)
		return
	}

	if *rawOnly {
		if _, err := io.Copy(out, rc); err != nil {
			fmt.Fprintf(os.Stderr, "Error getting url body: %v\n", err)
			os.Exit(1)
		}
		return
	}

	comment, _ := utf8.DecodeRuneInString(commentArg)

	// Create a reader for the Google Sheet
	gsr := gsheet2csv.NewReader(rc)
	gsr.QuotedComments = false
	gsr.Comment = 0
	gsr.ReuseRecord = true

	// Create CSV writer
	csvw := gsheet2csv.NewWriter(out)
	csvw.Comma = delim // Set delimiter to tab for TSV
	csvw.Comment = comment
	csvw.UseCRLF = *useCRLF
	for {
		// Convert each record
		record, err := gsr.Read()
		if err != nil {
			if errors.Is(err, io.EOF) {
				break
			}
			fmt.Fprintf(os.Stderr, "Error reading "+format+": %v\n", err)
			os.Exit(1)
		}

		if err := csvw.Write(record); err != nil {
			fmt.Fprintf(os.Stderr, "Error writing "+format+": %v\n", err)
			os.Exit(1)
		}
	}
	// Flush the writer to ensure all data is written
	csvw.Flush()
	if err := csvw.Error(); err != nil {
		fmt.Fprintf(os.Stderr, "Error flushing "+format+" writer: %v\n", err)
		os.Exit(1)
	}

	if out != os.Stdout {
		fmt.Fprintf(os.Stderr, "wrote %s\n", *outputFile)
	}
}