package main

import (
	"crypto/sha512"
	"encoding/base64"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strings"
)

type LicenseHash string

type License struct {
	LicenseType string
	Text        string
	// unique name of a license.
	LicenseName string
}

func hash(data string) string {
	hasher := sha512.New()
	hasher.Write([]byte(data))
	hash := hasher.Sum(nil)
	return base64.StdEncoding.EncodeToString(hash)
}

func detectLicenseType(content string) string {
	content = strings.ToLower(content)
	licenses := map[string]string{
		"mit":                "MIT License",
		"apache license":     "Apache License",
		"bsd":                "BSD License",
		"gnu general public": "GPL",
		"mozilla public":     "Mozilla Public License",
		"isc":                "ISC License",
		"creative commons":   "Creative Commons",
		"unlicense":          "Unlicense",
	}

	for key, license := range licenses {
		if strings.Contains(content, key) {
			return license
		}
	}
	return ""
}

func NewLicense(text string) *License {
	licenseType := detectLicenseType(text)
	return &License{
		LicenseType: licenseType,
		Text:        text,
	}
}

type Licenses map[string]*License

type Dependency struct {
	Module  string
	Version string
	Direct  bool
	License *License
}

func NewDependency(module string, version string, direct bool, license *License) *Dependency {
	return &Dependency{
		Module:  module,
		Version: version,
		Direct:  direct,
		License: license,
	}
}

type Dependencies []*Dependency

type Module struct {
	Licenses     Licenses
	Dependencies Dependencies
}

func NewModule(modules []ModuleDependency) *Module {
	module := &Module{
		Licenses:     Licenses{},
		Dependencies: Dependencies{},
	}
	for _, mod := range modules {
		if mod.Dir == "" {
			continue // Skip modules without local copies
		}
		license, err := module.findLicense(mod.Dir)
		if err != nil {
			log.Printf("ERROR: %v", err)
			continue
		}
		module.Licenses[hash(license.Text)] = license
		dependency := NewDependency(mod.Path, mod.Version, !mod.Indirect, license)
		module.Dependencies = append(module.Dependencies, dependency)
	}
	sort.Slice(module.Dependencies, func(i, j int) bool {
		direct1 := module.Dependencies[i].Direct
		direct2 := module.Dependencies[j].Direct
		if direct1 != direct2 {
			if direct1 {
				return true
			}
			return false
		}
		return module.Dependencies[i].Module < module.Dependencies[j].Module
	})

	return module
}

func (module Module) GenerateLicenseNames() {
	usedNames := make(map[string]bool)
	for _, license := range module.Licenses {
		basename := strings.ReplaceAll(license.LicenseType, " ", "_")
		i := 0
		name := fmt.Sprintf("%s-%d", basename, i)
		for usedNames[name] {
			i++
			name = fmt.Sprintf("%s-%d", basename, i)
		}
		license.LicenseName = name
		usedNames[name] = true
	}
}

func (module Module) DumpOverview() {
	// Find and print license information for each module
	fmt.Printf("%-50s %-20s %-10s %-20s %-20s\n", "MODULE", "VERSION", "DIRECT", "LICENSE", "HASH")
	fmt.Println()
	for _, dependency := range module.Dependencies {
		fmt.Printf("%-50s %-20s %-10v %-20s %-20s\n",
			truncateString(dependency.Module, 49),
			truncateString(dependency.Version, 19),
			dependency.Direct,
			dependency.License.LicenseType,
			dependency.License.LicenseName)
	}
}

func (module Module) DumpText(directOnly bool) {
	for _, dependency := range module.Dependencies {
		if directOnly && !dependency.Direct {
			continue
		}
		fmt.Println(strings.Repeat("=", 80))
		if dependency.Direct {
			fmt.Printf("Direct dependency")
		} else {
			fmt.Printf("Indirect dependency")
		}
		fmt.Printf(" %s %s\n", dependency.Module, dependency.Version)
		fmt.Printf("LICENSE\n\n %s\n\n",
			dependency.License.Text)
	}
}

func (module *Module) findLicense(dir string) (*License, error) {
	licenseFiles := []string{
		"LICENSE",
		"LICENSE.txt",
		"LICENSE.md",
		"license",
		"license.txt",
		"license.md",
	}

	for _, file := range licenseFiles {
		path := filepath.Join(dir, file)
		if _, err := os.Stat(path); err == nil {
			// Read first line of license file
			contentBytes, err := os.ReadFile(path)
			if err == nil {
				content := string(contentBytes)
				content = strings.TrimSpace(content)
				if len(content) > 0 {
					hashcode := hash(content)
					license := module.Licenses[hashcode]
					if license != nil {
						return license, nil
					}
					return NewLicense(content), nil
				}
			}
		}
	}
	return nil, fmt.Errorf("No license found in '%s'", dir)
}