package mime

import (
	"encoding/json"
	"fmt"
	"go/format"
	"io/ioutil"
	"os"
	"path"
	"text/template"
)

type Config struct {
	Source string

	Mimes       map[string][]string
	MimePrefix  string
	MimeTpl     string
	MimeResult  string
	MimePackage string

	Extensions map[string][]string
	ExtPrefix  string
	ExtTpl     string
	ExtResult  string
	ExtPackage string
}

func WithExtTpl(name string) Option {
	return func(c *Config) {
		c.ExtTpl = name
	}
}

func WithExtPacakge(name string) Option {
	return func(c *Config) {
		c.ExtPackage = name
	}
}

func WithExtResult(name string) Option {
	return func(c *Config) {
		c.ExtResult = name
	}
}

func WithMimeTpl(name string) Option {
	return func(c *Config) {
		c.MimeTpl = name
	}
}

func WithMimePackage(name string) Option {
	return func(c *Config) {
		c.MimePackage = name
	}
}

func WithMimeResult(name string) Option {
	return func(c *Config) {
		c.MimeResult = name
	}
}

type Option func(*Config)

func funcMap() template.FuncMap {
	return template.FuncMap{
		"name":  VarName,
		"value": Value,
	}
}

func Generate(fileName string, opts ...Option) error {
	cfg := Config{
		Source: fileName,

		ExtPrefix:  "Ext",
		ExtTpl:     "mime/tpl/extension.text.tmpl",
		ExtResult:  "extension.go",
		Extensions: make(map[string][]string),
		ExtPackage: "mime",

		MimeTpl:     "mime/tpl/mime.text.tmpl",
		Mimes:       make(map[string][]string),
		MimePrefix:  "",
		MimeResult:  "mime.go",
		MimePackage: "mime",
	}

	for _, opt := range opts {
		opt(&cfg)
	}

	data, err := os.ReadFile(fileName)
	if err != nil {
		return fmt.Errorf("read file:%w", err)
	}

	if err := json.Unmarshal(data, &cfg.Mimes); err != nil {
		return fmt.Errorf("unmarshal:%w", err)
	}

	cfg.Extensions = extensions(cfg.Mimes)

	template, err := template.New("mimes").Funcs(funcMap()).ParseFiles(cfg.ExtTpl, cfg.MimeTpl)
	if err != nil {
		return fmt.Errorf("ext template:%w", err)
	}

	extFile, err := os.Create(cfg.ExtResult)
	if err != nil {
		return fmt.Errorf("ext file:%w", err)
	}

	if err := template.ExecuteTemplate(extFile, path.Base(cfg.ExtTpl), cfg); err != nil {
		return fmt.Errorf("ext execute:%w", err)
	}

	if err := Format(extFile.Name()); err != nil {
		return fmt.Errorf("format ext:%w", err)
	}

	mimeFile, err := os.Create(cfg.MimeResult)
	if err != nil {
		return fmt.Errorf("mime file:%w", err)
	}

	if err := template.ExecuteTemplate(mimeFile, path.Base(cfg.MimeTpl), cfg); err != nil {
		return fmt.Errorf("mime execute:%w", err)
	}

	if err := Format(mimeFile.Name()); err != nil {
		return fmt.Errorf("format mime:%w", err)
	}

	return nil
}

// Format file and write it.
func Format(name string) error {
	in, err := ioutil.ReadFile(name)
	if err != nil {
		return err
	}
	out, err := format.Source(in)
	if err != nil {
		return err
	}

	file, err := os.Create(name)
	if err != nil {
		return fmt.Errorf("ext file:%w", err)
	}

	if _, err := file.Write(out); err != nil {
		return fmt.Errorf("write:%w", err)
	}

	return nil
}

func extensions(mimes map[string][]string) map[string][]string {
	out := make(map[string][]string)

	for mime, exts := range mimes {
		for _, ext := range exts {
			if _, ok := out[ext]; ok {
				out[ext] = append(out[ext], mime)
				continue
			}
			out[ext] = []string{ext}
		}
	}

	return out
}