Implement basic functionality of top-level DeadLinks type

deadlinks.go

@@ -15,93 +15,229 @@
 package deadlinks
 
 import (
+	"context"
 	"errors"
 	"fmt"
-	"net/url"
+	"regexp"
+	"runtime"
+	"sync"
 	"time"
+
+	"code.betamike.com/mediocregopher/mediocre-go-lib/miter"
 )
 
-// URL is a standard universal resource identifier, normalized particularly for
-// this package.
-type URL string
+// Opts are optional fields which can be provided to New. A nil Opts is
+// equivalent to an empty one.
+type Opts struct {
+	Client Client // Defaults to `NewClient(nil)`
+	Parser Parser // Defaults to `NewParser()`
 
-// 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
+	// Concurrency determines the maximum number of URLs which can be checked
+	// simultaneously.
+	//
+	// Default: `runtime.NumCPU()`
+	Concurrency int
+
+	// OnError, if set, will be called whenever DeadLinks encounters an error
+	// internally that it would otherwise skip over.
+	OnError func(error)
 }
 
-func parseURLs(urlStrs []string) ([]URL, error) {
+func (o *Opts) withDefaults() *Opts {
+	if o == nil {
+		o = new(Opts)
+	}
+
+	if o.Client == nil {
+		o.Client = NewClient(nil)
+	}
+
+	if o.Parser == nil {
+		o.Parser = NewParser()
+	}
+
+	if o.Concurrency == 0 {
+		o.Concurrency = runtime.NumCPU()
+	}
+
+	return o
+}
+
+// DeadLinks crawls a configured space of URLs and keeps track of any broken
+// links which it finds.
+//
+// DeadLinks supports multiple web protocols and document formats
+// out-of-the-box, and will traverse between them as necessary based on URL
+// schemas. See the `NewClient` and `NewParser` functions for more details.
+type DeadLinks struct {
+	opts     Opts
+	store    Store
+	patterns []*regexp.Regexp
+}
+
+// New initializes and returns a DeadLinks instance which will track the
+// liveness of the given set of pinned URLs, as well as all URLs linked to from
+// those. If a linked URL matches one of the given regexp patterns then any
+// URLs linked to from it will be tracked as well.
+//
+// If a non-empty Store is passed to New then whatever set of previously pinned
+// URLs were present will be overwritten with the given ones.
+func New(
+	ctx context.Context,
+	store Store,
+	pinnedURLStrs,
+	patternStrs []string,
+	opts *Opts,
+) (
+	*DeadLinks, error,
+) {
 	var (
-		res  = make([]URL, 0, len(urlStrs))
-		errs []error
+		err        error
+		pinnedURLs = make([]URL, len(pinnedURLStrs))
+		patterns   = make([]*regexp.Regexp, len(patternStrs))
 	)
-	for _, urlStr := range urlStrs {
-		u, err := ParseURL(urlStr)
-		if err == nil {
-			res = append(res, u)
-		} else {
-			errs = append(errs, err)
+
+	for i, u := range pinnedURLStrs {
+		if pinnedURLs[i], err = ParseURL(u); err != nil {
+			return nil, fmt.Errorf("parsing url %q: %w", u, err)
 		}
 	}
-	return res, errors.Join(errs...)
+
+	for i, p := range patternStrs {
+		if patterns[i], err = regexp.Compile(p); err != nil {
+			return nil, fmt.Errorf("compiling regexp %q: %w", p, err)
+		}
+	}
+
+	d := &DeadLinks{
+		opts:     *opts.withDefaults(),
+		store:    store,
+		patterns: patterns,
+	}
+
+	if err := d.store.SetPinned(ctx, pinnedURLs); err != nil {
+		return nil, fmt.Errorf("pinning URLs: %w", err)
+	}
+
+	return d, nil
 }
 
-func (u URL) toStd() *url.URL {
-	uu, err := url.Parse(string(u))
+func (d *DeadLinks) onError(ctx context.Context, err error) {
+	if d.opts.OnError == nil ||
+		(ctx.Err() != nil && errors.Is(err, ctx.Err())) {
+		return
+	}
+
+	d.opts.OnError(err)
+}
+
+func (d *DeadLinks) shouldFollowURL(url URL) bool {
+	urlStr := string(url)
+	for _, pattern := range d.patterns {
+		if pattern.MatchString(urlStr) {
+			return true
+		}
+	}
+	return false
+}
+
+func (d *DeadLinks) getURL(ctx context.Context, url URL) ([]URL, error) {
+	mimeType, body, err := d.opts.Client.Get(ctx, url)
 	if err != nil {
-		panic(fmt.Sprintf("parsing URL %q: %v", u, err))
+		return nil, err
 	}
-	return uu
+	defer body.Close()
+
+	if !d.shouldFollowURL(url) {
+		return nil, nil
+	}
+
+	return d.opts.Parser.Parse(mimeType, body)
 }
 
-// ResolveReference is equivalend to the method of the same name in `net/url`.
-func (u URL) ResolveReference(u2Str string) (URL, error) {
-	u2, err := url.Parse(u2Str)
+// checkURL only returns an error if storing the results of the check fails.
+func (d *DeadLinks) checkURL(ctx context.Context, url URL) error {
+	var (
+		now      = time.Now()
+		status   = ResourceStatusOK
+		errorStr string
+	)
+
+	outgoingURLs, err := d.getURL(ctx, url)
 	if err != nil {
-		return "", err
+		status = ResourceStatusError
+		errorStr = err.Error()
 	}
-	return URL(u.toStd().ResolveReference(u2).String()), nil
-}
 
-// 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))
+	err = d.store.Update(ctx, now, url, status, errorStr, outgoingURLs)
+	if err != nil {
+		return fmt.Errorf(
+			"failed storing status:%v (errorStr:%q) and %d outgoingURLs: %w",
+			status, errorStr, len(outgoingURLs), err,
+		)
 	}
+
+	return nil
 }
 
-// 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
+// Update runs through all pinned or previously discovered URLs which were
+// last checked prior to the given time (or which have never been checked) and
+// updates the internal storage with any new URLs and links to dead URLs which
+// it finds.
+func (d *DeadLinks) Update(
+	ctx context.Context, lastCheckedBefore time.Time,
+) error {
+	var (
+		wg = new(sync.WaitGroup)
+		ch = make(chan URL, d.opts.Concurrency)
+	)
 
-	// only set if Status == ResourceStatusError
-	ErrorString string
+	wg.Add(d.opts.Concurrency)
+	for i := 0; i < d.opts.Concurrency; i++ {
+		go func() {
+			defer wg.Done()
+			for url := range ch {
+				if err := d.checkURL(ctx, url); err != nil {
+					d.onError(ctx, fmt.Errorf("checking url %q: %w", url, err))
+				}
+			}
+		}()
+	}
 
-	// Indicate the URLs of resources which link to/are linked from this
-	// resource.
-	IncomingLinkURLs, OutgoingLinkURLs []URL
+	var err error
+
+	// Because checking URLs can result in new URLs being inserted into the
+	// Store, we query the Store in a loop until it stops producing
+	// unvisited/stale URLs.
+	for {
+		var (
+			n        int
+			urlsIter = d.store.GetURLsByLastChecked(lastCheckedBefore)
+		)
+
+		err = miter.ForEach(ctx, urlsIter, func(url URL) error {
+			ch <- url
+			n++
+			return nil
+		})
+
+		if err != nil || n == 0 {
+			break
+		}
+	}
+
+	close(ch)
+	wg.Wait()
+
+	if err != nil {
+		return fmt.Errorf("iterating urls needing checked: %w", err)
+	}
+
+	if err := d.store.GC(ctx); err != nil {
+		return fmt.Errorf("garbage collecting: %w", err)
+	}
+
+	return nil
 }
+
+// TODO expose GetByStatus

resource.go

@@ -0,0 +1,45 @@
+package deadlinks
+
+import (
+	"fmt"
+	"time"
+)
+
+// 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
+}

url.go

@@ -0,0 +1,53 @@
+package deadlinks
+
+import (
+	"errors"
+	"fmt"
+	"net/url"
+)
+
+// 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...)
+}
+
+func (u URL) toStd() *url.URL {
+	uu, err := url.Parse(string(u))
+	if err != nil {
+		panic(fmt.Sprintf("parsing URL %q: %v", u, err))
+	}
+	return uu
+}
+
+// ResolveReference is equivalend to the method of the same name in `net/url`.
+func (u URL) ResolveReference(u2Str string) (URL, error) {
+	u2, err := url.Parse(u2Str)
+	if err != nil {
+		return "", err
+	}
+	return URL(u.toStd().ResolveReference(u2).String()), nil
+}