package instruction

import (
	"fmt"
	"github.com/xdrm-brackets/nix-amer/internal/cnf"
	"os"
	"strings"
)

// ErrCannotSet is raised when there is an error trying to update
// a field
var ErrCannotSet = fmt.Errorf("cannot set the field")

type set struct {
	raw string
	// File is the path to the file
	File string
	// Path is the configuration field path
	Path string
	// Value if the value to add or update
	Value string
	// Format is the configuration format in use
	Format *cnf.ConfigurationFormat
}

func (d *set) Raw() string { return strings.Join([]string{"set", d.raw}, " ") }

func (d *set) Build(_args string) error {

	// 1. extract action (sub command)
	split := strings.Fields(_args)

	// 2. check path
	if len(split) < 2 {
		return fmt.Errorf("missing configuration path")
	}
	path := split[0]
	value := strings.Join(split[1:], "")

	// 3. check path separator
	splitPath := strings.Split(path, "@")
	if len(splitPath) > 2 {
		return fmt.Errorf("invalid path (additional '@'?)")
	}

	d.File = splitPath[0]
	if len(splitPath) > 1 { // add field path only if set
		d.Path = splitPath[1]
	}

	// add value
	d.Value = value
	d.raw = _args

	return nil
}

func (d set) Exec(ctx ExecutionContext) ([]byte, error) {

	// 1. get file / alias
	path := d.File
	if !strings.Contains(path, "/") {
		if p, exists := ctx.Alias[path]; exists {
			path = p
		}
	}

	// 2. fail if file not found
	if _, err := os.Stat(path); os.IsNotExist(err) {
		return nil, fmt.Errorf("cannot find file '%s'", path)
	}

	// 3. try to load format
	format, err := cnf.Load(path)
	if err != nil {
		return nil, err
	}

	// 4. try to update value
	if !format.Set(d.Path, d.Value) {
		return nil, ErrCannotSet
	}

	// 5. Update file
	file, err := os.OpenFile(path, os.O_WRONLY, 0)
	if err != nil {
		return nil, err
	}
	defer file.Close()
	if _, err = format.WriteTo(file); err != nil {
		return nil, err
	}

	return nil, nil

}