package bfcodegen

import (
	"errors"
	"fmt"
	"gogs.mikescher.com/BlackForestBytes/goext"
	"gogs.mikescher.com/BlackForestBytes/goext/cmdext"
	"gogs.mikescher.com/BlackForestBytes/goext/cryptext"
	"gogs.mikescher.com/BlackForestBytes/goext/langext"
	"gogs.mikescher.com/BlackForestBytes/goext/rext"
	"io"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strings"
	"time"
)

type CSIDDef struct {
	File         string
	FileRelative string
	Name         string
	Prefix       string
}

var rexCSIDPackage = rext.W(regexp.MustCompile(`^package\s+(?P<name>[A-Za-z0-9_]+)\s*$`))

var rexCSIDDef = rext.W(regexp.MustCompile(`^\s*type\s+(?P<name>[A-Za-z0-9_]+)\s+string\s*//\s*(@csid:type)\s+\[(?P<prefix>[A-Z0-9]{3})].*$`))

var rexCSIDChecksumConst = rext.W(regexp.MustCompile(`const ChecksumCharsetIDGenerator = "(?P<cs>[A-Za-z0-9_]*)"`))

func GenerateCharsetIDSpecs(sourceDir string, destFile string) error {

	files, err := os.ReadDir(sourceDir)
	if err != nil {
		return err
	}

	oldChecksum := "N/A"
	if _, err := os.Stat(destFile); !os.IsNotExist(err) {
		content, err := os.ReadFile(destFile)
		if err != nil {
			return err
		}
		if m, ok := rexCSIDChecksumConst.MatchFirst(string(content)); ok {
			oldChecksum = m.GroupByName("cs").Value()
		}
	}

	files = langext.ArrFilter(files, func(v os.DirEntry) bool { return v.Name() != path.Base(destFile) })
	files = langext.ArrFilter(files, func(v os.DirEntry) bool { return strings.HasSuffix(v.Name(), ".go") })
	files = langext.ArrFilter(files, func(v os.DirEntry) bool { return !strings.HasSuffix(v.Name(), "_gen.go") })
	langext.SortBy(files, func(v os.DirEntry) string { return v.Name() })

	newChecksumStr := goext.GoextVersion
	for _, f := range files {
		content, err := os.ReadFile(path.Join(sourceDir, f.Name()))
		if err != nil {
			return err
		}
		newChecksumStr += "\n" + f.Name() + "\t" + cryptext.BytesSha256(content)
	}

	newChecksum := cryptext.BytesSha256([]byte(newChecksumStr))

	if newChecksum != oldChecksum {
		fmt.Printf("[IDGenerate] Checksum has changed ( %s -> %s ), will generate new file\n\n", oldChecksum, newChecksum)
	} else {
		fmt.Printf("[IDGenerate] Checksum unchanged ( %s ), nothing to do\n", oldChecksum)
		return nil
	}

	allIDs := make([]CSIDDef, 0)

	pkgname := ""

	for _, f := range files {
		fmt.Printf("========= %s =========\n\n", f.Name())
		fileIDs, pn, err := processCSIDFile(sourceDir, path.Join(sourceDir, f.Name()))
		if err != nil {
			return err
		}

		fmt.Printf("\n")

		allIDs = append(allIDs, fileIDs...)

		if pn != "" {
			pkgname = pn
		}
	}

	if pkgname == "" {
		return errors.New("no package name found in any file")
	}

	err = os.WriteFile(destFile, []byte(fmtCSIDOutput(newChecksum, allIDs, pkgname)), 0o755)
	if err != nil {
		return err
	}

	res, err := cmdext.RunCommand("go", []string{"fmt", destFile}, langext.Ptr(2*time.Second))
	if err != nil {
		return err
	}

	if res.CommandTimedOut {
		fmt.Println(res.StdCombined)
		return errors.New("go fmt timed out")
	}
	if res.ExitCode != 0 {
		fmt.Println(res.StdCombined)
		return errors.New("go fmt did not succeed")
	}

	return nil
}

func processCSIDFile(basedir string, fn string) ([]CSIDDef, string, error) {
	file, err := os.Open(fn)
	if err != nil {
		return nil, "", err
	}

	defer func() { _ = file.Close() }()

	bin, err := io.ReadAll(file)
	if err != nil {
		return nil, "", err
	}

	lines := strings.Split(string(bin), "\n")

	ids := make([]CSIDDef, 0)

	pkgname := ""

	for i, line := range lines {
		if i == 0 && strings.HasPrefix(line, "// Code generated by") {
			break
		}

		if match, ok := rexCSIDPackage.MatchFirst(line); i == 0 && ok {
			pkgname = match.GroupByName("name").Value()
			continue
		}

		if match, ok := rexCSIDDef.MatchFirst(line); ok {

			rfp, err := filepath.Rel(basedir, fn)
			if err != nil {
				return nil, "", err
			}

			def := CSIDDef{
				File:         fn,
				FileRelative: rfp,
				Name:         match.GroupByName("name").Value(),
				Prefix:       match.GroupByName("prefix").Value(),
			}
			fmt.Printf("Found ID definition { '%s' }\n", def.Name)
			ids = append(ids, def)
		}
	}

	return ids, pkgname, nil
}

func fmtCSIDOutput(cs string, ids []CSIDDef, pkgname string) string {
	str := "// Code generated by id-generate.go DO NOT EDIT.\n"
	str += "\n"
	str += "package " + pkgname + "\n"
	str += "\n"

	str += `import "crypto/rand"` + "\n"
	str += `import "fmt"` + "\n"
	str += `import "github.com/go-playground/validator/v10"` + "\n"
	str += `import "github.com/rs/zerolog/log"` + "\n"
	str += `import "gogs.mikescher.com/BlackForestBytes/goext/exerr"` + "\n"
	str += `import "gogs.mikescher.com/BlackForestBytes/goext/langext"` + "\n"
	str += `import "gogs.mikescher.com/BlackForestBytes/goext/rext"` + "\n"
	str += `import "math/big"` + "\n"
	str += `import "reflect"` + "\n"
	str += `import "regexp"` + "\n"
	str += `import "strings"` + "\n"
	str += "\n"

	str += "const ChecksumCharsetIDGenerator = \"" + cs + "\" // GoExtVersion: " + goext.GoextVersion + "\n"
	str += "\n"

	str += "const idlen = 24\n"
	str += "\n"
	str += "const checklen = 1\n"
	str += "\n"
	str += `const idCharset = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"` + "\n"
	str += "const idCharsetLen = len(idCharset)\n"
	str += "\n"
	str += "var charSetReverseMap = generateCharsetMap()\n"
	str += "\n"
	str += "const (\n"
	for _, iddef := range ids {
		str += "	prefix" + iddef.Name + " = \"" + iddef.Prefix + "\"" + "\n"
	}
	str += ")\n"
	str += "\n"
	str += "var (\n"
	for _, iddef := range ids {
		str += "	regex" + iddef.Name + " = generateRegex(prefix" + iddef.Name + ")" + "\n"
	}
	str += ")\n"
	str += "\n"
	str += "func generateRegex(prefix string) rext.Regex {\n"
	str += "	return rext.W(regexp.MustCompile(fmt.Sprintf(\"^%s[%s]{%d}[%s]{%d}$\", prefix, idCharset, idlen-len(prefix)-checklen, idCharset, checklen)))\n"
	str += "}\n"
	str += "\n"

	str += `func generateCharsetMap() []int {` + "\n"
	str += `	result := make([]int, 128)` + "\n"
	str += `	for i := 0; i < len(result); i++ {` + "\n"
	str += `		result[i] = -1` + "\n"
	str += `	}` + "\n"
	str += `	for idx, chr := range idCharset {` + "\n"
	str += `		result[int(chr)] = idx` + "\n"
	str += `	}` + "\n"
	str += `	return result` + "\n"
	str += `}` + "\n"
	str += "\n"
	str += `func generateID(prefix string) string {` + "\n"
	str += `	k := ""` + "\n"
	str += `	max := big.NewInt(int64(idCharsetLen))` + "\n"
	str += `	checksum := 0` + "\n"
	str += `	for i := 0; i < idlen-len(prefix)-checklen; i++ {` + "\n"
	str += `		v, err := rand.Int(rand.Reader, max)` + "\n"
	str += `		if err != nil {` + "\n"
	str += `			panic(err)` + "\n"
	str += `		}` + "\n"
	str += `		v64 := v.Int64()` + "\n"
	str += `		k += string(idCharset[v64])` + "\n"
	str += `		checksum = (checksum + int(v64)) % (idCharsetLen)` + "\n"
	str += `	}` + "\n"
	str += `	checkstr := string(idCharset[checksum%idCharsetLen])` + "\n"
	str += `	return prefix + k + checkstr` + "\n"
	str += `}` + "\n"
	str += "\n"
	str += `func validateID(prefix string, value string) error {` + "\n"
	str += `	if len(value) != idlen {` + "\n"
	str += `		return exerr.New(exerr.TypeInvalidCSID, "id has the wrong length").Str("value", value).Build()` + "\n"
	str += `	}` + "\n"
	str += "\n"
	str += `	if !strings.HasPrefix(value, prefix) {` + "\n"
	str += `		return exerr.New(exerr.TypeInvalidCSID, "id is missing the correct prefix").Str("value", value).Str("prefix", prefix).Build()` + "\n"
	str += `	}` + "\n"
	str += "\n"
	str += `	checksum := 0` + "\n"
	str += `	for i := len(prefix); i < len(value)-checklen; i++ {` + "\n"
	str += `		ichr := int(value[i])` + "\n"
	str += `		if ichr < 0 || ichr >= len(charSetReverseMap) || charSetReverseMap[ichr] == -1 {` + "\n"
	str += `			return exerr.New(exerr.TypeInvalidCSID, "id contains invalid characters").Str("value", value).Build()` + "\n"
	str += `		}` + "\n"
	str += `		checksum = (checksum + charSetReverseMap[ichr]) % (idCharsetLen)` + "\n"
	str += `	}` + "\n"
	str += "\n"
	str += `	checkstr := string(idCharset[checksum%idCharsetLen])` + "\n"
	str += "\n"
	str += `	if !strings.HasSuffix(value, checkstr) {` + "\n"
	str += `		return exerr.New(exerr.ErrInvalidCSID, "id checkstring is invalid").Str("value", value).Str("checkstr", checkstr).Build()` + "\n"
	str += `	}` + "\n"
	str += "\n"
	str += `	return nil` + "\n"
	str += `}` + "\n"
	str += "\n"
	str += `func getRawData(prefix string, value string) string {` + "\n"
	str += `	if len(value) != idlen {` + "\n"
	str += `		return ""` + "\n"
	str += `	}` + "\n"
	str += `	return value[len(prefix) : idlen-checklen]` + "\n"
	str += `}` + "\n"
	str += "\n"
	str += `func getCheckString(prefix string, value string) string {` + "\n"
	str += `	if len(value) != idlen {` + "\n"
	str += `		return ""` + "\n"
	str += `	}` + "\n"
	str += `	return value[idlen-checklen:]` + "\n"
	str += `}` + "\n"
	str += "\n"
	str += `func ValidateEntityID(vfl validator.FieldLevel) bool {` + "\n"
	str += `	if !vfl.Field().CanInterface() {` + "\n"
	str += `		log.Error().Msgf("Failed to validate EntityID (cannot interface ?!?)")` + "\n"
	str += `		return false` + "\n"
	str += `	}` + "\n"
	str += "\n"
	str += `	ifvalue := vfl.Field().Interface()` + "\n"
	str += "\n"
	str += `	if value1, ok := ifvalue.(EntityID); ok {` + "\n"
	str += "\n"
	str += `		if vfl.Field().Type().Kind() == reflect.Pointer && langext.IsNil(value1) {` + "\n"
	str += `			return true` + "\n"
	str += `		}` + "\n"
	str += "\n"
	str += `		if err := value1.Valid(); err != nil {` + "\n"
	str += `			log.Debug().Msgf("Failed to validate EntityID '%s' (%s)", value1.String(), err.Error())` + "\n"
	str += `			return false` + "\n"
	str += `		} else {` + "\n"
	str += `			return true` + "\n"
	str += `		}` + "\n"
	str += "\n"
	str += `	} else {` + "\n"
	str += `		log.Error().Msgf("Failed to validate EntityID (wrong type: %T)", ifvalue)` + "\n"
	str += `		return false` + "\n"
	str += `	}` + "\n"
	str += `}` + "\n"
	str += "\n"

	for _, iddef := range ids {

		str += "// ================================ " + iddef.Name + " (" + iddef.FileRelative + ") ================================" + "\n"
		str += "" + "\n"

		str += "func New" + iddef.Name + "() " + iddef.Name + " {" + "\n"
		str += "	return " + iddef.Name + "(generateID(prefix" + iddef.Name + "))" + "\n"
		str += "}" + "\n"

		str += "" + "\n"

		str += "func (id " + iddef.Name + ") Valid() error {" + "\n"
		str += "	return validateID(prefix" + iddef.Name + ", string(id))" + "\n"
		str += "}" + "\n"

		str += "" + "\n"

		str += "func (i " + iddef.Name + ") String() string {" + "\n"
		str += "	return string(i)" + "\n"
		str += "}" + "\n"

		str += "" + "\n"

		str += "func (i " + iddef.Name + ") Prefix() string {" + "\n"
		str += "	return prefix" + iddef.Name + "" + "\n"
		str += "}" + "\n"

		str += "" + "\n"

		str += "func (id " + iddef.Name + ") Raw() string {" + "\n"
		str += "	return getRawData(prefix" + iddef.Name + ", string(id))" + "\n"
		str += "}" + "\n"

		str += "" + "\n"

		str += "func (id " + iddef.Name + ") CheckString() string {" + "\n"
		str += "	return getCheckString(prefix" + iddef.Name + ", string(id))" + "\n"
		str += "}" + "\n"

		str += "" + "\n"

		str += "func (id " + iddef.Name + ") Regex() rext.Regex {" + "\n"
		str += "	return regex" + iddef.Name + "" + "\n"
		str += "}" + "\n"

		str += "" + "\n"

	}

	return str
}