package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"os"
	"path/filepath"

	"dario.cat/mergo"
)

func newCLI(name, usage string) *CLI {
	cli := &CLI{}
	cli.FlagSet = flag.NewFlagSet(name, flag.ExitOnError)

	cli.FlagSet.Usage = func() {
		cli.Printf("Usage:\n")
		cli.Printf("  %s %s\n\n", name, usage)
		cli.FlagSet.PrintDefaults()
		cli.Printf("\n")
	}

	return cli
}

type CLI struct {
	*flag.FlagSet
}

func (cli *CLI) Printf(format string, args ...any) {
	_, _ = fmt.Fprintf(cli.FlagSet.Output(), format, args...)
}

func readFile(match string, dest any) error {
	data, err := os.ReadFile(match)
	if err != nil {
		return err
	}

	return json.Unmarshal(data, dest)
}

func main() {
	cli := newCLI("merge-swagger", "[opts] <glob...>")

	output := cli.String("output", "-", `Specify where the merged file should be written. "-" for stdout.`)

	err := cli.Parse(os.Args[1:])
	if err != nil {
		panic(err)
	}

	if cli.NArg() < 1 {
		cli.Usage()
		return
	}

	var all []string

	for _, arg := range cli.Args() {
		matches, err := filepath.Glob(arg)
		if err != nil {
			panic(err)
		}

		all = append(all, matches...)
	}

	full := map[string]interface{}{}

	for _, match := range all {
		data := map[string]interface{}{}

		err = readFile(match, &data)
		if err != nil {
			panic(err)
		}

		err = mergo.Merge(&full, data, mergo.WithOverride, mergo.WithAppendSlice)
		if err != nil {
			panic(err)
		}
	}

	full["consumes"] = []string{
		"application/json",
	}

	full["produces"] = []string{
		"application/json",
	}

	out := os.Stdout
	if output != nil && *output != "-" && *output != "" {
		out, err = os.Create(*output)
		if err != nil {
			panic(err)
		}

		defer out.Close()
	}

	enc := json.NewEncoder(out)
	enc.SetIndent("", "  ")
	_ = enc.Encode(full)
}