package edge

import (
	"context"
	"errors"
	"fmt"
	"io"
	"mime"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/carlosframework/platform/internal/registry"
	"github.com/carlosframework/platform/internal/release"
)

// reqStatic is one request the way a browser holding a cached copy makes it:
// no redirect following, no transparent gzip (an explicit Accept-Encoding
// turns the client's own off), and the validators in hdr.
func reqStatic(t *testing.T, method, base, path string, hdr map[string]string) (*http.Response, string) {
	t.Helper()
	req, err := http.NewRequest(method, base+path, nil)
	if err != nil {
		t.Fatalf("new request: %v", err)
	}
	req.Host = "site.example.com"
	for k, v := range hdr {
		req.Header.Set(k, v)
	}
	client := &http.Client{CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse }}
	resp, err := client.Do(req)
	if err != nil {
		t.Fatalf("%s %s%s: %v", method, base, path, err)
	}
	defer resp.Body.Close()
	b, err := io.ReadAll(resp.Body)
	if err != nil {
		t.Fatalf("%s %s%s: read body: %v", method, base, path, err)
	}
	return resp, string(b)
}

// siteServer ships files as version of app into its own store and serves it
// from a fresh handler, behind the same compression wrapper the edge applies.
func siteServer(t *testing.T, app, version string, files map[string]string) *httptest.Server {
	t.Helper()
	srv, _ := siteServerTree(t, app, version, files)
	return srv
}

// siteServerTree is siteServer that also says where version's tree is
// extracted, for the tests that reach under the handler.
func siteServerTree(t *testing.T, app, version string, files map[string]string) (*httptest.Server, string) {
	t.Helper()
	store := release.NewDirStore(filepath.Join(t.TempDir(), "store"))
	priv, pub := testKeys(t)
	shipSite(t, store, app, version, files)
	if err := release.Promote(context.Background(), store, priv, release.OpsAccount, app, "canary/x", version); err != nil {
		t.Fatalf("Promote %s: %v", version, err)
	}
	rt := registry.Route{Host: "site.example.com", Kind: "static", App: app, Channel: "canary/x", Status: "ready"}
	h := newStaticHandler(rt, store, pub, filepath.Join(t.TempDir(), "cache"))
	h.(*staticSite).recheck = 0
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if gw := newGzipWriter(w, r); gw != nil {
			w = gw
			defer gw.finish()
		}
		h.ServeHTTP(w, r)
	}))
	t.Cleanup(srv.Close)
	return srv, h.(*staticSite).dir(siteDirOf(t, store, app, version))
}

// A static response used to carry Last-Modified and nothing else, and a
// browser handed only that guesses a freshness lifetime — typically a tenth of
// the file's age — and reuses its copy without asking. A site last deployed a
// month ago kept showing the old page for days after the next deploy
// (discussion #195). no-cache makes every load ask; the ETag makes the answer
// a cheap 304 until the bytes actually change.
func TestStaticResponsesMakeTheBrowserRevalidate(t *testing.T) {
	_, _, _, srv := staticFixture(t)

	for _, path := range []string{"/", "/docs/page.html", "/style.css"} {
		resp, _ := reqStatic(t, "GET", srv.URL, path, nil)
		if resp.StatusCode != http.StatusOK {
			t.Fatalf("GET %s = %d, want 200", path, resp.StatusCode)
		}
		if got := resp.Header.Get("Cache-Control"); got != "no-cache" {
			t.Errorf("GET %s Cache-Control = %q, want %q", path, got, "no-cache")
		}
		if got := resp.Header.Get("ETag"); !strings.HasPrefix(got, `W/"`) || len(got) < 20 {
			t.Errorf("GET %s ETag = %q, want a weak content tag", path, got)
		}
		// The mtime of an extracted file is when THIS box unpacked it. It is
		// not a fact about the content and must not be offered as one.
		if got := resp.Header.Get("Last-Modified"); got != "" {
			t.Errorf("GET %s Last-Modified = %q, want none", path, got)
		}
	}

	// The tree's own 404 must not be cached on a guess either: the page it
	// stands in for may exist in the next deploy. It names no representation,
	// so it carries no validator.
	resp, _ := reqStatic(t, "GET", srv.URL, "/missing.html", nil)
	if resp.StatusCode != http.StatusNotFound {
		t.Fatalf("GET /missing.html = %d, want 404", resp.StatusCode)
	}
	if got := resp.Header.Get("Cache-Control"); got != "no-cache" {
		t.Errorf("404 Cache-Control = %q, want %q", got, "no-cache")
	}
	if got := resp.Header.Get("ETag"); got != "" {
		t.Errorf("404 ETag = %q, want none", got)
	}
}

// The validator is the file's CONTENT. Unchanged bytes revalidate to a 304 —
// across a deploy too, so a release that touched one page does not make every
// browser refetch every asset — and changed bytes answer 200, in both
// directions: a rollback is as much a change as a deploy.
func TestStaticValidatorFollowsTheContent(t *testing.T) {
	store, _, priv, srv := staticFixture(t)
	promote := func(ver string) {
		t.Helper()
		if err := release.Promote(context.Background(), store, priv, release.OpsAccount, "site", "canary/x", ver); err != nil {
			t.Fatalf("Promote %s: %v", ver, err)
		}
	}
	tagOf := func(path string) string {
		t.Helper()
		resp, _ := reqStatic(t, "GET", srv.URL, path, nil)
		tag := resp.Header.Get("ETag")
		if resp.StatusCode != http.StatusOK || tag == "" {
			t.Fatalf("GET %s = %d with ETag %q", path, resp.StatusCode, tag)
		}
		return tag
	}
	homeV1, cssV1 := tagOf("/"), tagOf("/style.css")
	if homeV1 == cssV1 {
		t.Fatalf("two different files share the tag %q", homeV1)
	}

	resp, _ := reqStatic(t, "GET", srv.URL, "/", map[string]string{"If-None-Match": homeV1})
	if resp.StatusCode != http.StatusNotModified {
		t.Fatalf("revalidating unchanged content = %d, want 304", resp.StatusCode)
	}
	// A 304 carries what its 200 would have: the cache updates from it.
	if got := resp.Header.Get("ETag"); got != homeV1 {
		t.Errorf("304 ETag = %q, want the 200's %q", got, homeV1)
	}
	if got := resp.Header.Get("Cache-Control"); got != "no-cache" {
		t.Errorf("304 Cache-Control = %q, want %q", got, "no-cache")
	}

	// v2 changes the home page and leaves the stylesheet byte-identical.
	shipSite(t, store, "site", "v2", map[string]string{"index.html": "home v2", "style.css": "body{}"})
	promote("v2")
	resp, body := reqStatic(t, "GET", srv.URL, "/", map[string]string{"If-None-Match": homeV1})
	if resp.StatusCode != http.StatusOK || body != "home v2" {
		t.Fatalf("revalidating a changed page after a deploy = %d %q, want 200 %q", resp.StatusCode, body, "home v2")
	}
	homeV2 := resp.Header.Get("ETag")
	if homeV2 == homeV1 {
		t.Fatalf("the changed page kept the tag %q", homeV1)
	}
	resp, _ = reqStatic(t, "GET", srv.URL, "/style.css", map[string]string{"If-None-Match": cssV1})
	if resp.StatusCode != http.StatusNotModified {
		t.Fatalf("revalidating an UNCHANGED file after a deploy = %d, want 304", resp.StatusCode)
	}

	promote("v1") // roll back
	resp, body = reqStatic(t, "GET", srv.URL, "/", map[string]string{"If-None-Match": homeV2})
	if resp.StatusCode != http.StatusOK || body != "home v1" {
		t.Fatalf("revalidating after a rollback = %d %q, want 200 %q", resp.StatusCode, body, "home v1")
	}
	if got := resp.Header.Get("ETag"); got != homeV1 {
		t.Errorf("the rolled-back page's tag = %q, want its original %q", got, homeV1)
	}
}

// A browser whose copy predates the ETag holds only the old Last-Modified and
// revalidates on the date alone. Against an extraction mtime that answer is
// wrong after a rollback — the tree rolled back to was unpacked BEFORE the one
// the browser holds, so "modified since?" says no. With no date offered there
// is nothing to compare, and the browser gets the bytes.
func TestStaticDateOnlyRevalidationGetsTheBytes(t *testing.T) {
	_, _, _, srv := staticFixture(t)
	resp, body := reqStatic(t, "GET", srv.URL, "/", map[string]string{
		"If-Modified-Since": "Fri, 01 Jan 2100 00:00:00 GMT",
	})
	if resp.StatusCode != http.StatusOK || body != "home v1" {
		t.Fatalf("date-only revalidation = %d %q, want 200 %q", resp.StatusCode, body, "home v1")
	}
}

// A version NAME is not a fact about the bytes. A pruned version can be
// re-shipped under its old name with different content, and a hostname can
// move between two apps that both have a "v1" — in either case a tag made of
// the name would let a browser keep the old page on a 304.
func TestStaticSameVersionNameDifferentContent(t *testing.T) {
	a := siteServer(t, "site", "v1", map[string]string{"index.html": "the first site"})
	b := siteServer(t, "other", "v1", map[string]string{"index.html": "a different site"})

	respA, _ := reqStatic(t, "GET", a.URL, "/", nil)
	tagA := respA.Header.Get("ETag")
	if tagA == "" {
		t.Fatal("no ETag from the first site")
	}
	resp, body := reqStatic(t, "GET", b.URL, "/", map[string]string{"If-None-Match": tagA})
	if resp.StatusCode != http.StatusOK || body != "a different site" {
		t.Fatalf("revalidating one v1 against another app's v1 = %d %q, want 200 %q", resp.StatusCode, body, "a different site")
	}

	// And identical bytes agree wherever they are served from — two edges
	// unpacking the same release must hand out the same tag.
	c := siteServer(t, "third", "v9", map[string]string{"index.html": "the first site"})
	resp, _ = reqStatic(t, "GET", c.URL, "/", map[string]string{"If-None-Match": tagA})
	if resp.StatusCode != http.StatusNotModified {
		t.Fatalf("identical bytes from another handler = %d, want 304", resp.StatusCode)
	}
}

// The edge gzips a compressible response and, because gzipped bytes are a
// different representation, weakens a strong ETag as it does — but only on
// the 200. A 304 and a HEAD pass through untouched, so a strong tag would
// come back weak on the page and strong on its revalidation, and a cache may
// not update the one from the other. A tag that is weak from the start reads
// the same on all three.
func TestStaticTagIsTheSameCompressedRevalidatedAndOnHead(t *testing.T) {
	page := "<html>" + strings.Repeat("a page big enough to be worth compressing. ", 200) + "</html>"
	srv := siteServer(t, "site", "v1", map[string]string{"index.html": page})
	gz := map[string]string{"Accept-Encoding": "gzip"}

	resp, _ := reqStatic(t, "GET", srv.URL, "/", gz)
	if resp.StatusCode != http.StatusOK || resp.Header.Get("Content-Encoding") != "gzip" {
		t.Fatalf("GET / = %d, Content-Encoding %q; want a gzipped 200", resp.StatusCode, resp.Header.Get("Content-Encoding"))
	}
	tag := resp.Header.Get("ETag")
	if !strings.HasPrefix(tag, `W/"`) {
		t.Fatalf("gzipped 200 ETag = %q, want a weak tag", tag)
	}

	resp, _ = reqStatic(t, "GET", srv.URL, "/", map[string]string{"Accept-Encoding": "gzip", "If-None-Match": tag})
	if resp.StatusCode != http.StatusNotModified {
		t.Fatalf("revalidating the gzipped page = %d, want 304", resp.StatusCode)
	}
	if got := resp.Header.Get("ETag"); got != tag {
		t.Errorf("304 ETag = %q, want the 200's %q", got, tag)
	}

	resp, _ = reqStatic(t, "HEAD", srv.URL, "/", gz)
	if got := resp.Header.Get("ETag"); got != tag {
		t.Errorf("HEAD ETag = %q, want the GET's %q", got, tag)
	}
	// Asked for by name: with no Accept-Encoding of its own the Go client
	// requests gzip and hides that it did.
	resp, body := reqStatic(t, "GET", srv.URL, "/", map[string]string{"Accept-Encoding": "identity"})
	if resp.StatusCode != http.StatusOK || body != page || resp.Header.Get("Content-Encoding") != "" {
		t.Fatalf("identity GET = %d, Content-Encoding %q, %d bytes; want the plain page", resp.StatusCode, resp.Header.Get("Content-Encoding"), len(body))
	}
	if got := resp.Header.Get("ETag"); got != tag {
		t.Errorf("identity GET ETag = %q, want the gzipped GET's %q", got, tag)
	}
}

// What http.ServeFile gave for free and this handler must keep now that it
// serves the file itself: the canonical redirect off /index.html, ranges, and
// the refusal of a path with a ".." element.
func TestStaticKeepsServeFileBehaviour(t *testing.T) {
	_, _, _, srv := staticFixture(t)

	resp, _ := reqStatic(t, "GET", srv.URL, "/index.html?x=1", nil)
	if resp.StatusCode != http.StatusMovedPermanently || resp.Header.Get("Location") != "./?x=1" {
		t.Fatalf("GET /index.html = %d, Location %q; want 301 to ./?x=1", resp.StatusCode, resp.Header.Get("Location"))
	}

	resp, body := reqStatic(t, "GET", srv.URL, "/", map[string]string{"Range": "bytes=0-3"})
	if resp.StatusCode != http.StatusPartialContent || body != "home" {
		t.Fatalf("ranged GET = %d %q, want 206 %q", resp.StatusCode, body, "home")
	}
	// A weak tag cannot vouch for a byte range: If-Range falls back to the
	// whole file, which is the safe answer and the documented cost.
	tag := resp.Header.Get("ETag")
	resp, body = reqStatic(t, "GET", srv.URL, "/", map[string]string{"Range": "bytes=0-3", "If-Range": tag})
	if resp.StatusCode != http.StatusOK || body != "home v1" {
		t.Fatalf("If-Range with a weak tag = %d %q, want the full 200", resp.StatusCode, body)
	}

	req, err := http.NewRequest("GET", srv.URL+"/", nil)
	if err != nil {
		t.Fatal(err)
	}
	req.Host = "site.example.com"
	req.URL.Opaque = "/docs/../index.html" // sent as written, not cleaned by the client
	resp2, err := http.DefaultClient.Do(req)
	if err != nil {
		t.Fatal(err)
	}
	resp2.Body.Close()
	if resp2.StatusCode != http.StatusBadRequest {
		t.Fatalf("a path with a .. element = %d, want 400", resp2.StatusCode)
	}
}

// The same bytes can be two representations. /about as an extensionless file
// is sniffed as text/plain; redeployed as about/index.html it is text/html,
// byte for byte the same. A tag made of the bytes alone would answer 304 and
// leave the browser rendering markup as text.
func TestStaticTagCoversTheContentType(t *testing.T) {
	store, _, priv, srv := staticFixture(t)
	const same = "Hello <em>world</em>"
	shipSite(t, store, "site", "v2", map[string]string{"index.html": "home", "about": same})
	if err := release.Promote(context.Background(), store, priv, release.OpsAccount, "site", "canary/x", "v2"); err != nil {
		t.Fatalf("Promote v2: %v", err)
	}
	resp, _ := reqStatic(t, "GET", srv.URL, "/about", nil)
	plainTag, plainType := resp.Header.Get("ETag"), resp.Header.Get("Content-Type")
	if resp.StatusCode != http.StatusOK || !strings.HasPrefix(plainType, "text/plain") {
		t.Fatalf("GET /about = %d %q, want a text/plain 200", resp.StatusCode, plainType)
	}

	shipSite(t, store, "site", "v3", map[string]string{"index.html": "home", "about/index.html": same})
	if err := release.Promote(context.Background(), store, priv, release.OpsAccount, "site", "canary/x", "v3"); err != nil {
		t.Fatalf("Promote v3: %v", err)
	}
	resp, body := reqStatic(t, "GET", srv.URL, "/about", map[string]string{"If-None-Match": plainTag})
	if resp.StatusCode != http.StatusOK || body != same || !strings.HasPrefix(resp.Header.Get("Content-Type"), "text/html") {
		t.Fatalf("revalidating /about after it became HTML = %d %q; want a text/html 200", resp.StatusCode, resp.Header.Get("Content-Type"))
	}
}

// openTagged writes body at dir/name and opens it the way serveTree does.
func openTagged(t *testing.T, dir, name, body string) (string, *os.File, os.FileInfo) {
	t.Helper()
	fp := filepath.Join(dir, name)
	if err := os.WriteFile(fp, []byte(body), 0o644); err != nil {
		t.Fatal(err)
	}
	f, err := os.Open(fp)
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { f.Close() })
	fi, err := f.Stat()
	if err != nil {
		t.Fatal(err)
	}
	return fp, f, fi
}

// A cold file is hashed ONCE however many requests arrive for it together.
// Without that, a burst of requests against one large uncached asset — HEADs
// and one-byte ranges included — would each read and hash the whole file
// before sending a byte.
//
// The overlap is forced, not hoped for: the first hash is held until every
// other caller is known to be waiting on it.
func TestTagCacheHashesAColdFileOnceForOverlappingRequests(t *testing.T) {
	c := newTagCache()
	c.wait = time.Minute
	held, release := make(chan struct{}), make(chan struct{})
	var heldOnce, releaseOnce sync.Once
	c.hold = func() { heldOnce.Do(func() { close(held) }); <-release }
	letGo := func() { releaseOnce.Do(func() { close(release) }) }
	defer letGo() // a failure below must not strand the callers
	dir := t.TempDir()
	if err := os.WriteFile(filepath.Join(dir, "big.bin"), []byte(strings.Repeat("x", 4096)), 0o644); err != nil {
		t.Fatal(err)
	}
	const callers = 12
	tags := make([]string, callers)
	errs := make([]error, callers)
	var wg sync.WaitGroup
	call := func(i int) {
		defer wg.Done()
		fp := filepath.Join(dir, "big.bin")
		f, err := os.Open(fp)
		if err != nil {
			errs[i] = err
			return
		}
		defer f.Close()
		fi, err := f.Stat()
		if err != nil {
			errs[i] = err
			return
		}
		tags[i], _, errs[i] = c.tag(context.Background(), fp, f, fi)
	}
	wg.Add(1)
	go call(0)
	<-held // the first caller is inside its hash
	for i := 1; i < callers; i++ {
		wg.Add(1)
		go call(i)
	}
	deadline := time.Now().Add(10 * time.Second)
	for c.waiting.Load() != callers-1 {
		if time.Now().After(deadline) {
			t.Fatalf("%d of %d callers are waiting on the hash in flight", c.waiting.Load(), callers-1)
		}
		time.Sleep(time.Millisecond)
	}
	letGo()
	wg.Wait()
	for i := range tags {
		if errs[i] != nil || tags[i] == "" || tags[i] != tags[0] {
			t.Fatalf("caller %d = %q, %v; want every caller to get %q", i, tags[i], errs[i], tags[0])
		}
	}
	if got := c.hashed.Load(); got != 1 {
		t.Fatalf("the file was hashed %d times for %d overlapping callers, want once", got, callers)
	}
}

// Large files hash a few at a time, and a request that cannot get a turn —
// or whose file is still being hashed for someone else — is not made to wait
// for it: past a short budget it is served without a tag. A small file never
// queues behind them at all. Otherwise four requests for four large cold
// assets would hold up the first load of every other static site on the box.
func TestTagCacheDoesNotQueueBehindLargeHashes(t *testing.T) {
	c := newTagCache()
	c.wait = 20 * time.Millisecond
	dir := t.TempDir()
	for i := 0; i < tagHashers; i++ {
		c.sem <- struct{}{} // every hasher busy with someone's large asset
	}

	fp, f, fi := openTagged(t, dir, "big.bin", strings.Repeat("x", tagInline+1))
	if _, _, err := c.tag(context.Background(), fp, f, fi); !errors.Is(err, errTagBusy) {
		t.Fatalf("a large file with no free hasher = %v, want errTagBusy", err)
	}
	if n := len(c.flights); n != 0 {
		t.Fatalf("%d flights left registered after giving up", n)
	}

	fp, f, fi = openTagged(t, dir, "page.html", "<p>a small page</p>")
	tag, ctype, err := c.tag(context.Background(), fp, f, fi)
	if err != nil || tag == "" || !strings.HasPrefix(ctype, "text/html") {
		t.Fatalf("a small file while every hasher is busy = %q %q %v; want it tagged at once", tag, ctype, err)
	}

	// Once a hasher frees up the large file is tagged, and stays tagged.
	// The budget is lifted first: at 20ms a stalled scheduler could find the
	// timer and the free hasher ready together, and pick the timer.
	<-c.sem
	c.wait = time.Minute
	fp, f, fi = openTagged(t, dir, "big.bin", strings.Repeat("x", tagInline+1))
	if tag, _, err := c.tag(context.Background(), fp, f, fi); err != nil || tag == "" {
		t.Fatalf("a large file with a free hasher = %q, %v", tag, err)
	}
}

// The tag covers the Content-Type the response will carry, not the extension
// it was derived from: two boxes with different MIME tables type the same
// bytes differently, and a 304 from one must not confirm the other's page.
func TestTagCacheTagCoversTheResolvedContentType(t *testing.T) {
	c := newTagCache()
	const body = "# notes\n\nsome text\n"
	// The MIME table is process-wide and an added type stays added, so each
	// run takes an extension of its own (-count=N would otherwise find the
	// last run's mapping in place of an unknown one).
	ext := fmt.Sprintf(".zzcarlos%d", time.Now().UnixNano())
	fp, f, fi := openTagged(t, t.TempDir(), "notes"+ext, body)
	sniffedTag, sniffedType, err := c.tag(context.Background(), fp, f, fi)
	if err != nil || !strings.HasPrefix(sniffedType, "text/plain") {
		t.Fatalf("an unknown extension = %q %v, want it sniffed as text/plain", sniffedType, err)
	}

	// "Another box": the same bytes under the same name, with the type known.
	if err := mime.AddExtensionType(ext, "text/markdown; charset=utf-8"); err != nil {
		t.Fatal(err)
	}
	fp, f, fi = openTagged(t, t.TempDir(), "notes"+ext, body)
	knownTag, knownType, err := c.tag(context.Background(), fp, f, fi)
	if err != nil || !strings.HasPrefix(knownType, "text/markdown") {
		t.Fatalf("a mapped extension = %q %v, want text/markdown", knownType, err)
	}
	if knownTag == sniffedTag {
		t.Fatalf("the same bytes typed %q and %q share the tag %s", sniffedType, knownType, knownTag)
	}
}

// A remembered tag describes the file it was computed from, not the path. If
// the tree is replaced on disk under a live handler — cache maintenance, then
// another handler unpacking a re-shipped version of the same name — the old
// tag must not be handed out over the new bytes, nor a 304 against it.
func TestStaticTagDoesNotOutliveTheFileItDescribes(t *testing.T) {
	srv, tree := siteServerTree(t, "site", "v1", map[string]string{"index.html": "home", "style.css": "body{}"})
	resp, _ := reqStatic(t, "GET", srv.URL, "/style.css", nil)
	oldTag := resp.Header.Get("ETag")
	if oldTag == "" {
		t.Fatal("no ETag for /style.css")
	}

	// Replace the file the way a fresh extraction would — a new file renamed
	// into place — and make it the hardest case to notice: the same length
	// and the same mtime, so only the file's identity gives it away.
	fp := filepath.Join(tree, "style.css")
	before, err := os.Stat(fp)
	if err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(fp+".new", []byte("main{}"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.Chtimes(fp+".new", before.ModTime(), before.ModTime()); err != nil {
		t.Fatal(err)
	}
	if err := os.Rename(fp+".new", fp); err != nil {
		t.Fatal(err)
	}

	resp, body := reqStatic(t, "GET", srv.URL, "/style.css", map[string]string{"If-None-Match": oldTag})
	if resp.StatusCode != http.StatusOK || body != "main{}" {
		t.Fatalf("revalidating against a replaced file = %d %q, want 200 with the new bytes", resp.StatusCode, body)
	}
	if got := resp.Header.Get("ETag"); got == "" || got == oldTag {
		t.Fatalf("ETag over the replaced file = %q, want a new tag (old %q)", got, oldTag)
	}
}

// A file that is there and cannot be read is not a missing page. ServeFile
// said 403, and an operator reading the access log must still be able to tell
// a broken cache from a mistyped URL.
func TestStaticUnreadableFileIsNotA404(t *testing.T) {
	if os.Geteuid() == 0 {
		t.Skip("root reads through file modes")
	}
	srv, tree := siteServerTree(t, "site", "v1", map[string]string{"index.html": "home", "style.css": "body{}"})
	reqStatic(t, "GET", srv.URL, "/", nil) // extract the tree
	fp := filepath.Join(tree, "style.css")
	if err := os.Chmod(fp, 0); err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { os.Chmod(fp, 0o644) })
	resp, _ := reqStatic(t, "GET", srv.URL, "/style.css", nil)
	if resp.StatusCode != http.StatusForbidden {
		t.Fatalf("GET of an unreadable file = %d, want 403", resp.StatusCode)
	}
}

// failingFile reads like a file whose later blocks are bad: the first good
// bytes come back, then every read fails. Seeks work.
type failingFile struct {
	data []byte
	good int
	pos  int64
}

func (f *failingFile) Read(p []byte) (int, error) {
	if f.pos >= int64(f.good) {
		return 0, errors.New("input/output error")
	}
	n := copy(p, f.data[f.pos:f.good])
	f.pos += int64(n)
	return n, nil
}

func (f *failingFile) Seek(off int64, whence int) (int64, error) {
	switch whence {
	case io.SeekStart:
		f.pos = off
	case io.SeekCurrent:
		f.pos += off
	case io.SeekEnd:
		f.pos = int64(len(f.data)) + off
	}
	return f.pos, nil
}

// A hash that fails part-way must hand the file back at its start. The
// handler then serves it untagged, and net/http sniffs the Content-Type from
// wherever the file is positioned: left mid-file, an extensionless image
// would go out as text/plain.
func TestTagCacheRewindsTheFileWhenHashingFails(t *testing.T) {
	c := newTagCache()
	_, _, fi := openTagged(t, t.TempDir(), "picture", "placeholder")
	for _, good := range []int{100, 2000} { // fails inside the sniffed prefix, and after it
		f := &failingFile{data: make([]byte, 4096), good: good}
		if _, _, err := c.tag(context.Background(), fmt.Sprintf("/nowhere/picture-%d", good), f, fi); err == nil {
			t.Fatalf("hashing a file that fails after %d bytes reported no error", good)
		}
		if f.pos != 0 {
			t.Fatalf("after a failed hash (%d good bytes) the file is at offset %d, want 0", good, f.pos)
		}
	}
	if n := len(c.entries); n != 0 {
		t.Fatalf("%d tags remembered from hashes that failed", n)
	}
}