package bfcodegen

import (
	"bytes"
	_ "embed"
	"errors"
	"fmt"
	"go/format"
	"gogs.mikescher.com/BlackForestBytes/goext"
	"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"
	"text/template"
)

type EnumDefVal struct {
	VarName     string
	Value       string
	Description *string
}

type EnumDef struct {
	File         string
	FileRelative string
	EnumTypeName string
	Type         string
	Values       []EnumDefVal
}

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

var rexEnumDef = rext.W(regexp.MustCompile(`^\s*type\s+(?P<name>[A-Za-z0-9_]+)\s+(?P<type>[A-Za-z0-9_]+)\s*//\s*(@enum:type).*$`))

var rexEnumValueDef = rext.W(regexp.MustCompile(`^\s*(?P<name>[A-Za-z0-9_]+)\s+(?P<type>[A-Za-z0-9_]+)\s*=\s*(?P<value>("[A-Za-z0-9_:\s\-.]+"|[0-9]+))\s*(//(?P<descr>.*))?.*$`))

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

//go:embed enum-generate.template
var templateEnumGenerateText string

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

	allEnums := make([]EnumDef, 0)

	pkgname := ""

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

		fmt.Printf("\n")

		allEnums = append(allEnums, fileEnums...)

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

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

	fdata, err := format.Source([]byte(fmtEnumOutput(newChecksum, allEnums, pkgname)))
	if err != nil {
		return err
	}

	err = os.WriteFile(destFile, fdata, 0o755)
	if err != nil {
		return err
	}

	return nil
}

func processEnumFile(basedir string, fn string) ([]EnumDef, 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")

	enums := make([]EnumDef, 0)

	pkgname := ""

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

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

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

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

			def := EnumDef{
				File:         fn,
				FileRelative: rfp,
				EnumTypeName: match.GroupByName("name").Value(),
				Type:         match.GroupByName("type").Value(),
				Values:       make([]EnumDefVal, 0),
			}
			enums = append(enums, def)
			fmt.Printf("Found enum definition { '%s' -> '%s' }\n", def.EnumTypeName, def.Type)
		}

		if match, ok := rexEnumValueDef.MatchFirst(line); ok {
			typename := match.GroupByName("type").Value()
			def := EnumDefVal{
				VarName:     match.GroupByName("name").Value(),
				Value:       match.GroupByName("value").Value(),
				Description: match.GroupByNameOrEmpty("descr").ValueOrNil(),
			}

			found := false
			for i, v := range enums {
				if v.EnumTypeName == typename {
					enums[i].Values = append(enums[i].Values, def)
					found = true
					if def.Description != nil {
						fmt.Printf("Found enum value [%s] for '%s'  ('%s')\n", def.Value, def.VarName, *def.Description)
					} else {
						fmt.Printf("Found enum value [%s] for '%s'\n", def.Value, def.VarName)
					}
					break
				}
			}
			if !found {
				fmt.Printf("Found non-enum value [%s] for '%s' ( looks like enum value, but no matching @enum:type )\n", def.Value, def.VarName)
			}
		}
	}

	return enums, pkgname, nil
}

func fmtEnumOutput(cs string, enums []EnumDef, pkgname string) string {

	templ := template.New("enum-generate")

	templ = templ.Funcs(template.FuncMap{
		"boolToStr": func(b bool) string { return langext.Conditional(b, "true", "false") },
		"deref":     func(v *string) string { return *v },
		"trimSpace": func(str string) string { return strings.TrimSpace(str) },
		"hasStr":    func(v EnumDef) bool { return v.Type == "string" },
		"hasDescr": func(v EnumDef) bool {
			return langext.ArrAll(v.Values, func(val EnumDefVal) bool { return val.Description != nil })
		},
	})

	templ = template.Must(templ.Parse(templateEnumGenerateText))

	buffer := bytes.Buffer{}

	err := templ.Execute(&buffer, langext.H{
		"PkgName":      pkgname,
		"Checksum":     cs,
		"GoextVersion": goext.GoextVersion,
		"Enums":        enums,
	})
	if err != nil {
		panic(err)
	}

	return buffer.String()
}