package config

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"

	"gopkg.in/yaml.v3"
)

// Config is the on-disk settings file. Add fields here as the tool grows.
type Config struct {
	// ReposRoots are parent directories scanned (one level deep) for git repos.
	ReposRoots []string `yaml:"repos_roots"`
	// DevDir is the `dev` repo: holds commands/awsmfa, docker-compose.yml, bin/*.sh.
	DevDir string `yaml:"dev_dir"`
	// LegacyDir is the `legacy` repo: holds rundev.sh for prod-data console tools.
	LegacyDir string `yaml:"legacy_dir"`
}

// ErrNotSet means the config file does not exist yet.
var ErrNotSet = errors.New("config not set")

// Path returns the config file location: $XDG_CONFIG_HOME/mydev/config.yaml,
// falling back to ~/.config/mydev/config.yaml on all platforms.
func Path() (string, error) {
	base := os.Getenv("XDG_CONFIG_HOME")
	if base == "" {
		home, err := os.UserHomeDir()
		if err != nil {
			return "", err
		}
		base = filepath.Join(home, ".config")
	}
	return filepath.Join(base, "mydev", "config.yaml"), nil
}

// Load reads and parses the config file. Returns ErrNotSet (wrapped) if the
// file does not exist — callers should surface that as a clear "run config init".
func Load() (*Config, error) {
	path, err := Path()
	if err != nil {
		return nil, err
	}
	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, fmt.Errorf("%w: no config at %s — run 'mydev config init'", ErrNotSet, path)
		}
		return nil, err
	}
	var c Config
	if err := yaml.Unmarshal(data, &c); err != nil {
		return nil, fmt.Errorf("parse %s: %w", path, err)
	}
	return &c, nil
}

// --- validated accessors: each errors clearly when its setting is missing ---

func (c *Config) requireDev() (string, error) {
	if c.DevDir == "" {
		return "", errors.New("dev_dir not set in config — add it and retry")
	}
	return c.DevDir, nil
}

func (c *Config) requireLegacy() (string, error) {
	if c.LegacyDir == "" {
		return "", errors.New("legacy_dir not set in config — add it and retry")
	}
	return c.LegacyDir, nil
}

// AWSMFA returns the path to the awsmfa command inside dev_dir.
func (c *Config) AWSMFA() (string, error) {
	dev, err := c.requireDev()
	if err != nil {
		return "", err
	}
	return filepath.Join(dev, "commands", "awsmfa"), nil
}

// ComposeFile returns the dev docker-compose.yml path.
func (c *Config) ComposeFile() (string, error) {
	dev, err := c.requireDev()
	if err != nil {
		return "", err
	}
	return filepath.Join(dev, "docker-compose.yml"), nil
}

// DevBin returns the path to a script under dev_dir/bin.
func (c *Config) DevBin(script string) (string, error) {
	dev, err := c.requireDev()
	if err != nil {
		return "", err
	}
	return filepath.Join(dev, "bin", script), nil
}

// LegacyRunDev returns the legacy rundev.sh path (runs cmds in the container).
func (c *Config) LegacyRunDev() (string, error) {
	legacy, err := c.requireLegacy()
	if err != nil {
		return "", err
	}
	return filepath.Join(legacy, "rundev.sh"), nil
}

const sample = `# MyDev config

# Parent directories scanned one level deep for git repos.
repos_roots:
  - %[1]s/code

# The 'dev' repo — provides commands/awsmfa, docker-compose.yml, bin/*.sh.
dev_dir: %[1]s/code/dev

# The 'legacy' repo — provides rundev.sh for prod-data console tools.
legacy_dir: %[1]s/code/legacy
`

// Init writes a starter config file if none exists. Returns the path written.
// Refuses to overwrite an existing file.
func Init() (string, error) {
	path, err := Path()
	if err != nil {
		return "", err
	}
	if _, err := os.Stat(path); err == nil {
		return path, fmt.Errorf("config already exists at %s", path)
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return "", err
	}
	home, _ := os.UserHomeDir()
	if home == "" {
		home = "/Users/you"
	}
	if err := os.WriteFile(path, []byte(fmt.Sprintf(sample, home)), 0o644); err != nil {
		return "", err
	}
	return path, nil
}