package profile

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"os"

	"golang.org/x/sys/unix"
)

// ReadOnlyLoad reads and validates Profile configuration without creating,
// chmodding, chowning, locking, or replacing any filesystem object.
func (s *FileStore) ReadOnlyLoad() (State, error) {
	file, err := os.OpenFile(s.path, unix.O_RDONLY|unix.O_NOFOLLOW|unix.O_NONBLOCK, 0)
	if errors.Is(err, fs.ErrNotExist) {
		return State{}, nil
	}
	if err != nil {
		return State{}, fmt.Errorf("open Profile configuration read-only: %w", err)
	}
	defer file.Close()
	info, err := file.Stat()
	if err != nil {
		return State{}, fmt.Errorf("inspect Profile configuration: %w", err)
	}
	if !info.Mode().IsRegular() {
		return State{}, errors.New("Profile configuration is not a regular file")
	}
	data, err := io.ReadAll(file)
	if err != nil {
		return State{}, fmt.Errorf("read Profile configuration: %w", err)
	}
	var state State
	if err := json.Unmarshal(data, &state); err != nil {
		return State{}, fmt.Errorf("parse Profile configuration: %w", err)
	}
	for _, candidate := range state.Profiles {
		if _, err := ValidateAndNormalize(candidate); err != nil {
			return State{}, fmt.Errorf("Profile %q is invalid: %w", candidate.Name, err)
		}
	}
	if state.ActiveProfile != "" && indexProfile(state.Profiles, state.ActiveProfile) < 0 {
		return State{}, fmt.Errorf("Active Profile %q does not exist", state.ActiveProfile)
	}
	return state, nil
}

func indexProfile(profiles []Profile, name string) int {
	for i := range profiles {
		if profiles[i].Name == name {
			return i
		}
	}
	return -1
}