// Package config resolves and manages .hf-config.json relative to the binary directory.
package config

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

const configFileName = ".hf-config.json"

// Config holds the CLI configuration.
type Config struct {
	BaseURL string `json:"base-url"`
}

// DefaultConfig returns a Config with sensible defaults.
func DefaultConfig() Config {
	return Config{
		BaseURL: "http://127.0.0.1:8000",
	}
}

// BinaryDir returns the directory containing the running binary.
func BinaryDir() (string, error) {
	exe, err := os.Executable()
	if err != nil {
		return "", fmt.Errorf("cannot resolve binary path: %w", err)
	}
	exe, err = filepath.EvalSymlinks(exe)
	if err != nil {
		return "", fmt.Errorf("cannot resolve binary symlinks: %w", err)
	}
	return filepath.Dir(exe), nil
}

// ConfigPath returns the full path to the config file.
func ConfigPath() (string, error) {
	dir, err := BinaryDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(dir, configFileName), nil
}

// Load reads the config file. If the file does not exist, returns DefaultConfig.
func Load() (Config, error) {
	p, err := ConfigPath()
	if err != nil {
		return DefaultConfig(), err
	}
	data, err := os.ReadFile(p)
	if err != nil {
		if os.IsNotExist(err) {
			return DefaultConfig(), nil
		}
		return DefaultConfig(), fmt.Errorf("cannot read config: %w", err)
	}
	var cfg Config
	if err := json.Unmarshal(data, &cfg); err != nil {
		return DefaultConfig(), fmt.Errorf("invalid config JSON: %w", err)
	}
	if cfg.BaseURL == "" {
		cfg.BaseURL = DefaultConfig().BaseURL
	}
	return cfg, nil
}

// Save writes the config to the config file path.
func Save(cfg Config) error {
	p, err := ConfigPath()
	if err != nil {
		return err
	}
	data, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		return fmt.Errorf("cannot marshal config: %w", err)
	}
	data = append(data, '\n')
	if err := os.WriteFile(p, data, 0644); err != nil {
		return fmt.Errorf("cannot write config: %w", err)
	}
	return nil
}

// UpdateURL loads the existing config, updates the base-url, and saves.
func UpdateURL(url string) error {
	cfg, _ := Load()
	cfg.BaseURL = url
	return Save(cfg)
}