package builder

import (
	"fmt"
	"os"
	"regexp"
	"strings"

	"gopkg.in/yaml.v3"
)

// repoNameRegex validates repository names for safe use in NATS subjects.
// Only allows alphanumeric, dashes, and underscores (no dots or wildcards).
var repoNameRegex = regexp.MustCompile(`^[a-zA-Z0-9_-]+$`)

// validURLPrefixes are the allowed prefixes for repository URLs.
var validURLPrefixes = []string{
	"git+https://",
	"git+ssh://",
	"git+file://",
}

// RepoConfig holds configuration for a single repository.
type RepoConfig struct {
	URL           string `yaml:"url"`
	DefaultBranch string `yaml:"default_branch"`
}

// Config holds the builder configuration.
type Config struct {
	Repos map[string]RepoConfig `yaml:"repos"`
}

// LoadConfig loads configuration from a YAML file.
func LoadConfig(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to read config file: %w", err)
	}

	var cfg Config
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("failed to parse config file: %w", err)
	}

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

	return &cfg, nil
}

// Validate checks that the configuration is valid.
func (c *Config) Validate() error {
	if len(c.Repos) == 0 {
		return fmt.Errorf("no repos configured")
	}

	for name, repo := range c.Repos {
		// Validate repo name for safe use in NATS subjects
		if !repoNameRegex.MatchString(name) {
			return fmt.Errorf("repo name %q contains invalid characters (only alphanumeric, dash, underscore allowed)", name)
		}

		if repo.URL == "" {
			return fmt.Errorf("repo %q: url is required", name)
		}

		// Validate URL format
		validURL := false
		for _, prefix := range validURLPrefixes {
			if strings.HasPrefix(repo.URL, prefix) {
				validURL = true
				break
			}
		}
		if !validURL {
			return fmt.Errorf("repo %q: url must start with git+https://, git+ssh://, or git+file://", name)
		}

		if repo.DefaultBranch == "" {
			return fmt.Errorf("repo %q: default_branch is required", name)
		}
	}

	return nil
}

// GetRepo returns the configuration for a repository, or an error if not found.
func (c *Config) GetRepo(name string) (*RepoConfig, error) {
	repo, ok := c.Repos[name]
	if !ok {
		return nil, fmt.Errorf("repo %q not found in configuration", name)
	}
	return &repo, nil
}