package config

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

// ResolveHome returns the effective home for config/data paths.
// TASK_MASTER_HOME overrides the real user home (useful for demos/dev sandboxes).
func ResolveHome() (string, error) {
	if h := strings.TrimSpace(os.Getenv(envHome)); h != "" {
		return filepath.Clean(h), nil
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("resolve home directory: %w", err)
	}
	return home, nil
}

// LoadOrCreate loads the config from disk, creating defaults if missing.
// It also ensures DataDir and the active project directory exist.
func LoadOrCreate() (*Config, error) {
	home, err := ResolveHome()
	if err != nil {
		return nil, err
	}

	cfgPath := Path(home)
	cfgDir := filepath.Dir(cfgPath)
	if err := os.MkdirAll(cfgDir, 0o755); err != nil {
		return nil, fmt.Errorf("create config dir %s: %w", cfgDir, err)
	}

	cfg, err := readOrCreate(cfgPath, home)
	if err != nil {
		return nil, err
	}

	if d := strings.TrimSpace(os.Getenv(envDataDir)); d != "" {
		cfg.DataDir = filepath.Clean(d)
	}

	if err := ensureDataDirs(cfg); err != nil {
		return nil, err
	}

	return cfg, nil
}

func readOrCreate(cfgPath, home string) (*Config, error) {
	data, err := os.ReadFile(cfgPath)
	if err != nil {
		if os.IsNotExist(err) {
			cfg := Defaults(home)
			if err := Save(&cfg); err != nil {
				return nil, fmt.Errorf("write default config: %w", err)
			}
			return &cfg, nil
		}
		return nil, fmt.Errorf("read config %s: %w", cfgPath, err)
	}

	var cfg Config
	if err := json.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parse config %s: %w", cfgPath, err)
	}
	cfg.ApplyDefaults(home)
	return &cfg, nil
}

// Save writes the config to ~/.config/task-master/config.json
// (or under TASK_MASTER_HOME when set).
func Save(cfg *Config) error {
	home, err := ResolveHome()
	if err != nil {
		return err
	}

	cfgPath := Path(home)
	if err := os.MkdirAll(filepath.Dir(cfgPath), 0o755); err != nil {
		return fmt.Errorf("create config dir: %w", err)
	}

	data, err := json.MarshalIndent(cfg, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal config: %w", err)
	}
	data = append(data, '\n')

	if err := os.WriteFile(cfgPath, data, 0o644); err != nil {
		return fmt.Errorf("write config %s: %w", cfgPath, err)
	}
	return nil
}

func ensureDataDirs(cfg *Config) error {
	if err := os.MkdirAll(cfg.DataDir, 0o755); err != nil {
		return fmt.Errorf("create data dir %s: %w", cfg.DataDir, err)
	}
	projectDir := filepath.Join(cfg.DataDir, "projects", cfg.ActiveProject)
	if err := os.MkdirAll(projectDir, 0o755); err != nil {
		return fmt.Errorf("create project dir %s: %w", projectDir, err)
	}
	return nil
}