package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
)

const defaultBaseURL = "http://localhost:8010"

// Config is the persisted CLI credential state. It is stored as JSON at
// credentialsPath with 0600 permissions.
type Config struct {
	BaseURL string
	Token   string
}

// credentialsPath returns the on-disk location of the credentials file,
// os.UserConfigDir()/atlas9/credentials.json.
func credentialsPath() (string, error) {

	dir, err := os.UserConfigDir()
	if err != nil {
		return "", fmt.Errorf("locating config dir: %w", err)
	}
	return filepath.Join(dir, "atlas9", "credentials.json"), nil
}

// loadConfig reads the credentials file. A missing file is not an error; it
// yields an empty Config.
func loadConfig() (Config, error) {

	var cfg Config

	path, err := credentialsPath()
	if err != nil {
		return cfg, err
	}

	data, err := os.ReadFile(path)
	if errors.Is(err, fs.ErrNotExist) {
		return cfg, nil
	}
	if err != nil {
		return cfg, fmt.Errorf("reading credentials: %w", err)
	}
	if err := json.Unmarshal(data, &cfg); err != nil {
		return cfg, fmt.Errorf("parsing credentials: %w", err)
	}
	return cfg, nil
}

// saveConfig writes the credentials file with 0600 permissions, creating the
// parent directory as needed.
func saveConfig(cfg Config) error {

	path, err := credentialsPath()
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
		return fmt.Errorf("creating config dir: %w", err)
	}

	data, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		return err
	}
	if err := os.WriteFile(path, data, 0600); err != nil {
		return fmt.Errorf("writing credentials: %w", err)
	}
	return nil
}

// resolve merges the stored config with flag and environment overrides. The
// base URL precedence is flag > environment > file, and finally a built-in
// default. The token has no flag: it comes from the ATLAS9_TOKEN env var, else
// the stored file. An empty string means "not set" at each layer.
func resolve(stored Config, flagURL string) Config {

	out := stored

	if v := os.Getenv("ATLAS9_URL"); v != "" {
		out.BaseURL = v
	}
	if v := os.Getenv("ATLAS9_TOKEN"); v != "" {
		out.Token = v
	}
	if flagURL != "" {
		out.BaseURL = flagURL
	}
	if out.BaseURL == "" {
		out.BaseURL = defaultBaseURL
	}
	return out
}