package imgcache

import (
	"net/url"
	"strings"
)

// HostWhitelist implements the Whitelist interface for checking allowed source hosts.
// Only exact host matches are supported. Leading dots in patterns are stripped
// (e.g. ".example.com" becomes an exact match for "example.com").
type HostWhitelist struct {
	// hosts contains hosts that must match exactly (e.g., "cdn.example.com")
	hosts map[string]struct{}
}

// NewHostWhitelist creates a whitelist from a list of host patterns.
// All patterns are treated as exact matches. Leading dots are stripped
// for backwards compatibility (e.g. ".example.com" matches "example.com" only).
func NewHostWhitelist(patterns []string) *HostWhitelist {
	w := &HostWhitelist{
		hosts: make(map[string]struct{}),
	}

	for _, pattern := range patterns {
		pattern = strings.ToLower(strings.TrimSpace(pattern))
		if pattern == "" {
			continue
		}

		// Strip leading dot — suffix matching is not supported.
		// ".example.com" is treated as exact match for "example.com".
		pattern = strings.TrimPrefix(pattern, ".")

		if pattern == "" {
			continue
		}

		w.hosts[pattern] = struct{}{}
	}

	return w
}

// IsWhitelisted checks if a URL's host is in the whitelist.
// Only exact host matches are supported.
func (w *HostWhitelist) IsWhitelisted(u *url.URL) bool {
	if u == nil {
		return false
	}

	host := strings.ToLower(u.Hostname())
	if host == "" {
		return false
	}

	_, ok := w.hosts[host]

	return ok
}

// IsEmpty returns true if the whitelist has no entries.
func (w *HostWhitelist) IsEmpty() bool {
	return len(w.hosts) == 0
}

// Count returns the total number of whitelist entries.
func (w *HostWhitelist) Count() int {
	return len(w.hosts)
}