package cloudinit

import (
	"fmt"
	"os"

	"gopkg.in/yaml.v3"
)

// Parse reads a cloud-init YAML file and returns the parsed config.
func Parse(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading cloud-init file %s: %w", path, err)
	}
	return ParseBytes(data)
}

// ParseBytes parses cloud-init YAML from a byte slice.
func ParseBytes(data []byte) (*Config, error) {
	var cfg Config
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parsing cloud-init YAML: %w", err)
	}

	if err := validate(&cfg); err != nil {
		return nil, fmt.Errorf("validating cloud-init config: %w", err)
	}

	// Apply defaults
	if cfg.Network.Mode == "" {
		cfg.Network.Mode = "dhcp"
	}

	return &cfg, nil
}

func validate(cfg *Config) error {
	switch cfg.Network.Mode {
	case "", "dhcp":
		// valid
	case "static":
		if cfg.Network.Address == "" {
			return fmt.Errorf("static network mode requires 'address' field")
		}
		if cfg.Network.Gateway == "" {
			return fmt.Errorf("static network mode requires 'gateway' field")
		}
	default:
		return fmt.Errorf("unknown network mode: %q (expected 'dhcp' or 'static')", cfg.Network.Mode)
	}

	return nil
}