//go:build ignore

package main

import (
	"archive/tar"
	"bufio"
	"bytes"
	"compress/gzip"
	"errors"
	"flag"
	"fmt"
	"go/format"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"unicode"

	"github.com/kenshaw/snaker"
)

func main() {
	out := flag.String("out", "capvals.go", "out file")
	cache := flag.String("cache", ".cache", "cache directory")
	ver := flag.String("ver", "", "version")
	flag.Parse()
	if err := run(*out, *cache, *ver); err != nil {
		fmt.Fprintf(os.Stderr, "error: %v\n", err)
		os.Exit(1)
	}
}

func run(dest, cache, ver string) error {
	// get version
	ver, err := getVer(ver)
	if err != nil {
		return err
	}
	// get archive
	buf, err := get(cache, ver)
	if err != nil {
		return err
	}
	// load caps file
	caps, err := load(buf, ver)
	if err != nil {
		return err
	}
	// process caps
	buf, err = processCaps(caps)
	if err != nil {
		return err
	}
	// write
	buf, err = format.Source(buf)
	if err != nil {
		return err
	}
	return ioutil.WriteFile(dest, buf, 0o644)
}

func getVer(ver string) (string, error) {
	if ver != "" {
		return ver, nil
	}
	res, err := http.Get("https://ftp.gnu.org/pub/gnu/ncurses/")
	if err != nil {
		return "", err
	}
	defer res.Body.Close()
	buf, err := io.ReadAll(res.Body)
	if err != nil {
		return "", err
	}
	m := verRE.FindAllStringSubmatch(string(buf), -1)
	sort.Slice(m, func(i, j int) bool {
		va, _ := strconv.Atoi(m[i][1])
		vb, _ := strconv.Atoi(m[j][1])
		if va == vb {
			va, _ = strconv.Atoi(m[i][2])
			vb, _ = strconv.Atoi(m[j][2])
			return va > vb
		}
		return va > vb
	})
	return m[0][1] + "." + m[0][2], nil
}

var verRE = regexp.MustCompile(`href="ncurses-([0-9]+)\.([0-9]+)\.tar\.gz"`)

// get retrieves a file either from the the http path, or from disk.
func get(cache, ver string) ([]byte, error) {
	file := fmt.Sprintf("https://ftp.gnu.org/pub/gnu/ncurses/ncurses-%s.tar.gz", ver)
	if err := os.MkdirAll(cache, 0o755); err != nil {
		return nil, err
	}
	// check if the file exists
	cacheFile := filepath.Join(cache, filepath.Base(file))
	fi, err := os.Stat(cacheFile)
	if err == nil && !fi.IsDir() {
		log.Printf("loading %s", cacheFile)
		return ioutil.ReadFile(cacheFile)
	}
	// retrieve
	log.Printf("retrieving %s", file)
	res, err := http.Get(file)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()
	// read
	buf, err := ioutil.ReadAll(res.Body)
	if err != nil {
		return nil, err
	}
	// cache
	log.Printf("saving %s", cacheFile)
	if err := ioutil.WriteFile(cacheFile, buf, 0o644); err != nil {
		return nil, err
	}
	return buf, nil
}

// load extracts a file from a tar.gz.
func load(buf []byte, ver string) ([]byte, error) {
	file := fmt.Sprintf("ncurses-%s/include/Caps", ver)
	// create gzip reader
	gr, err := gzip.NewReader(bytes.NewReader(buf))
	if err != nil {
		return nil, err
	}
	defer gr.Close()
	// walk files in tar
	tr := tar.NewReader(gr)
	for {
		h, err := tr.Next()
		if err == io.EOF {
			break
		} else if err != nil {
			return nil, err
		}
		// found file, read contents
		if h.Name == file {
			b := bytes.NewBuffer(make([]byte, h.Size))
			var n int64
			n, err = io.Copy(b, tr)
			if err != nil {
				return nil, err
			}
			// check that all bytes were copied
			if n != h.Size {
				return nil, errors.New("could not read entire file")
			}
			return b.Bytes(), nil
		}
	}
	return nil, fmt.Errorf("could not load file %s", file)
}

// processCaps processes the data in the Caps file.
func processCaps(capsBuf []byte) ([]byte, error) {
	// create scanner
	s := bufio.NewScanner(bytes.NewReader(capsBuf))
	s.Buffer(make([]byte, 1024*1024), 1024*1024)
	// storage
	bools, nums, strs := new(bytes.Buffer), new(bytes.Buffer), new(bytes.Buffer)
	var boolCount, numCount, stringCount int
	var lastBool, lastNum, lastString string
	var boolNames, numNames, stringNames []string
	// process caps
	var n int
	for s.Scan() {
		// read line
		line := strings.TrimSpace(commentRE.ReplaceAllString(strings.Trim(s.Text(), "\x00"), ""))
		if len(line) == 0 || strings.HasPrefix(line, "capalias") || strings.HasPrefix(line, "infoalias") {
			continue
		}
		// split line's columns
		row := make([]string, 8)
		for i := 0; i < 7; i++ {
			start := strings.IndexFunc(line, unicode.IsSpace)
			end := strings.IndexFunc(line[start:], notSpace)
			row[i] = strings.TrimSpace(line[:start+end])
			line = line[start+end:]
		}
		row[7] = strings.TrimSpace(line)
		// manipulation
		var buf *bytes.Buffer
		var names *[]string
		var typ, isFirst, prefix, suffix string
		// format variable name
		name := snaker.SnakeToCamel(row[0])
		switch row[2] {
		case "bool":
			if boolCount == 0 {
				isFirst = " = iota"
			}
			buf, names, lastBool, prefix, suffix = bools, &boolNames, name, "indicates", ""
			typ = "bool"
			boolCount++
		case "num":
			if numCount == 0 {
				isFirst = " = iota"
			}
			buf, names, lastNum, prefix, suffix = nums, &numNames, name, "is", ""
			typ = "num"
			numCount++
		case "str":
			if stringCount == 0 {
				isFirst = " = iota"
			}
			buf, names, lastString, prefix, suffix = strs, &stringNames, name, "is the", ""
			typ = "string"
			stringCount++
		default:
			return nil, fmt.Errorf("line %d is invalid, has type: %s", n, row[2])
		}
		if isFirst == "" {
			buf.WriteString("\n")
		}
		fmt.Fprintf(buf, "// The %s [%s, %s] %s capability %s\n%s%s", name, row[0], row[1], typ, formatComment(row[7], prefix, suffix), name, isFirst)
		*names = append(*names, row[0], row[1])
		n++
	}
	if err := s.Err(); err != nil {
		return nil, err
	}
	f := new(bytes.Buffer)
	f.WriteString(hdr)
	// add consts
	typs := []string{"Bool", "Num", "String"}
	for i, b := range []*bytes.Buffer{bools, nums, strs} {
		f.WriteString(fmt.Sprintf("// %s capabilities.\nconst (\n", typs[i]))
		b.WriteTo(f)
		f.WriteString(")\n")
	}
	// add counts
	f.WriteString("const (\n")
	f.WriteString(fmt.Sprintf("// CapCountBool is the count of bool capabilities.\nCapCountBool = %s+1\n", lastBool))
	f.WriteString(fmt.Sprintf("// CapCountNum is the count of num capabilities.\nCapCountNum = %s+1\n", lastNum))
	f.WriteString(fmt.Sprintf("// CapCountString is the count of string capabilities.\nCapCountString = %s+1\n", lastString))
	f.WriteString(")\n")
	// add names
	z := []string{"bool", "num", "string"}
	for n, s := range [][]string{boolNames, numNames, stringNames} {
		y := z[n]
		f.WriteString(fmt.Sprintf("// %sCapNames are the %s term cap names.\n", y, y))
		f.WriteString(fmt.Sprintf("var %sCapNames = [...]string{\n", y))
		for i := 0; i < len(s); i += 2 {
			f.WriteString(fmt.Sprintf(`"%s", "%s",`+"\n", s[i], s[i+1]))
		}
		f.WriteString("}\n")
	}
	return f.Bytes(), nil
}

// formatComment formats comments with prefix and suffix.
func formatComment(s, prefix, suffix string) string {
	s = strings.TrimPrefix(s, prefix)
	s = strings.TrimSuffix(s, ".")
	s = strings.TrimSuffix(s, suffix)
	return strings.TrimSpace(prefix+" "+s+" "+suffix) + "."
}

func notSpace(r rune) bool {
	return !unicode.IsSpace(r)
}

var commentRE = regexp.MustCompile(`^#.*`)

const hdr = `package terminfo
	// Code generated by gen.go. DO NOT EDIT.
`