// Package deadlinks implements a liveness checker for hyperlinks in HTML and
// gemtext documents.
//
// # Storage
//
// By default DeadLinks uses an in-memory SQLite database for tracking the
// status of resources and the links between them. If memory usage becomes a
// problem it is also possible to use a SQLite database file:
//
//	store := deadlinks.NewSQLiteStore(&deadlinks.SQLiteStoreOpts{
//		Path: "/path/to/db/file.sqlite",
//	})
//
//	// TODO initialize DeadLinks
package deadlinks

import (
	"errors"
	"fmt"
	"net/url"
	"time"
)

// URL is a standard universal resource identifier, normalized particularly for
// this package.
type URL string

// ParseURL parses and returns a URL based on the given string, or an error.
func ParseURL(urlStr string) (URL, error) {
	u, err := url.Parse(urlStr)
	if err != nil {
		return "", err
	}
	return URL(u.String()), nil
}

func parseURLs(urlStrs []string) ([]URL, error) {
	var (
		res  = make([]URL, 0, len(urlStrs))
		errs []error
	)
	for _, urlStr := range urlStrs {
		u, err := ParseURL(urlStr)
		if err == nil {
			res = append(res, u)
		} else {
			errs = append(errs, err)
		}
	}
	return res, errors.Join(errs...)
}

// ResourceStatus describes what state a particular Resource is in.
type ResourceStatus int

// Enumeration of ResourceStatus values.
const (
	ResourceStatusUnknown ResourceStatus = iota
	ResourceStatusOK
	ResourceStatusError
)

func (ds ResourceStatus) String() string {
	switch ds {
	case ResourceStatusUnknown:
		return "UNKNOWN"
	case ResourceStatusOK:
		return "OK"
	case ResourceStatusError:
		return "ERROR"
	default:
		panic(fmt.Sprintf("unknown ResourceStatus: %#v", ds))
	}
}

// Resource describes the current state of a resource, with the resource being
// uniquely identified by a URL.
type Resource struct {
	URL         URL
	Status      ResourceStatus
	Pinned      bool
	LastChecked time.Time

	// only set if Status == ResourceStatusError
	ErrorString string

	// Indicate the URLs of resources which link to/are linked from this
	// resource.
	IncomingLinkURLs, OutgoingLinkURLs []URL
}