package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"html/template"
	"io"
	"io/fs"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"

	sprig "github.com/Masterminds/sprig/v3"
)

type valFileSlice []string

func (v *valFileSlice) String() string {
	return fmt.Sprintf("%v", *v)
}

func (v *valFileSlice) Set(value string) error {
	*v = append(*v, value)
	return nil
}

type valEnt struct {
	address []string
	v       string
}

type valSlice []valEnt

func (v *valSlice) String() string {
	return fmt.Sprintf("%v", *v)
}

func (v *valSlice) Set(value string) error {
	pieces := strings.Split(value, "=")
	if len(pieces) < 2 {
		return fmt.Errorf("Invalid value setting.")
	}
	*v = append(*v, valEnt{
		strings.Split(pieces[0], "."),
		pieces[1],
	})
	return nil
}

var flags struct {
	valuesFiles valFileSlice
	values      valSlice
}

func init() {
	flag.Var(&flags.values, "set", "")
	flag.Var(&flags.valuesFiles, "f", "")
	flag.Parse()
}

func checkErr(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "ERROR: %+v", err)
		os.Exit(1)
	}
}

func expandFiles(files []string) (expFiles []string) {
	expFiles = []string{}
	for _, path := range files {
		fileInfo, err := os.Stat(path)
		checkErr(err)

		if fileInfo.IsDir() {
			filepath.WalkDir(path, func(path string, d fs.DirEntry, err error) error {
				if err != nil {
					fmt.Fprintf(os.Stderr, "WARN: %+v", err)
					return err
				}
				if d.IsDir() {
					return nil
				}
				expFiles = append(expFiles, path)
				return nil
			})
		} else {
			expFiles = append(expFiles, path)
		}
	}
	return
}

func mergeValues() (result map[string]interface{}) {
	result = map[string]interface{}{}
	for _, vf := range flags.valuesFiles {
		vfContent, err := ioutil.ReadFile(vf)
		checkErr(err)
		err = json.Unmarshal(vfContent, result)
		checkErr(err)
	}
	for i, v := range flags.values {
		subMap := result
		for _, node := range v.address {
			if i == len(v.address)-1 {
				subMap[node] = v.v
			} else {
				if _, ok := subMap[node]; !ok {
					subMap[node] = map[string]interface{}{}
				}
				subMap = subMap[node].(map[string]interface{})
			}
		}
	}
	return
}

func main() {
	var err error
	tpl := template.New("base").Funcs(sprig.FuncMap())
	if len(flag.Args()) == 0 || (len(flag.Args()) == 1 && flag.Args()[0] == "-") {
		var data []byte
		data, err = io.ReadAll(os.Stdin)
		checkErr(err)
		tpl, err = tpl.Parse(string(data))
		checkErr(err)
	} else {
		tpl, err = tpl.ParseFiles(expandFiles(flag.Args())...)
		checkErr(err)
	}
	tpl.Execute(os.Stdout, mergeValues())
}