feat: add tooltip support for PDF files

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Breaking: Go version 1.17 is now the minimum required version to build this. (#292)
 - Breaking: Thumbnail generation now requires libvips. See [docs/build.md](./docs/build.md) for prerequisite instructions. (#366, #369)
 - Breaking: Resolver caches are now stored in PostgreSQL. See [docs/build.md](./docs/build.md) for prerequisite instructions. (#271)
+- PDF: Generate customized tooltips for PDF files. (#374)
 - Twitter: Generate thumbnails with all images of a tweet. (#373)
 - YouTube: Added support for 'YouTube shorts' URLs. (#299)
 - Fix: SevenTV emotes now resolve correctly. (#281, #288, #307)

go.mod

@@ -17,6 +17,7 @@ require (
 	github.com/nicklaw5/helix v1.25.0
 	github.com/pashagolub/pgxmock v1.8.0
 	github.com/patrickmn/go-cache v2.1.0+incompatible
+	github.com/pdfcpu/pdfcpu v0.3.13
 	github.com/prometheus/client_golang v1.13.0
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.13.0
@@ -43,6 +44,8 @@ require (
 	github.com/googleapis/gax-go/v2 v2.5.1 // indirect
 	github.com/hashicorp/golang-lru v0.5.5-0.20200511160909-eb529947af53 // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
+	github.com/hhrutter/lzw v0.0.0-20190829144645-6f07a24e8650 // indirect
+	github.com/hhrutter/tiff v0.0.0-20190829141212-736cae8d0bc7 // indirect
 	github.com/jackc/chunkreader/v2 v2.0.1 // indirect
 	github.com/jackc/pgio v1.0.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
@@ -58,6 +61,7 @@ require (
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/pelletier/go-toml v1.9.5 // indirect
 	github.com/pelletier/go-toml/v2 v2.0.5 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	github.com/prometheus/client_model v0.2.0 // indirect
 	github.com/prometheus/common v0.37.0 // indirect
 	github.com/prometheus/procfs v0.8.0 // indirect
@@ -71,7 +75,7 @@ require (
 	go.uber.org/multierr v1.6.0 // indirect
 	golang.org/x/crypto v0.0.0-20220722155217-630584e8d5aa // indirect
 	golang.org/x/exp/typeparams v0.0.0-20220722155223-a9213eeb770e // indirect
-	golang.org/x/image v0.0.0-20200927104501-e162460cd6b5 // indirect
+	golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb // indirect
 	golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 // indirect
 	golang.org/x/net v0.0.0-20221012135044-0b7e1fb9d458 // indirect
 	golang.org/x/oauth2 v0.0.0-20221006150949-b44042a4b9c1 // indirect

go.sum

@@ -197,6 +197,11 @@ github.com/hashicorp/golang-lru v0.5.5-0.20200511160909-eb529947af53 h1:mcyf48Fj
 github.com/hashicorp/golang-lru v0.5.5-0.20200511160909-eb529947af53/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
 github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
+github.com/hhrutter/lzw v0.0.0-20190827003112-58b82c5a41cc/go.mod h1:yJBvOcu1wLQ9q9XZmfiPfur+3dQJuIhYQsMGLYcItZk=
+github.com/hhrutter/lzw v0.0.0-20190829144645-6f07a24e8650 h1:1yY/RQWNSBjJe2GDCIYoLmpWVidrooriUr4QS/zaATQ=
+github.com/hhrutter/lzw v0.0.0-20190829144645-6f07a24e8650/go.mod h1:yJBvOcu1wLQ9q9XZmfiPfur+3dQJuIhYQsMGLYcItZk=
+github.com/hhrutter/tiff v0.0.0-20190829141212-736cae8d0bc7 h1:o1wMw7uTNyA58IlEdDpxIrtFHTgnvYzA8sCQz8luv94=
+github.com/hhrutter/tiff v0.0.0-20190829141212-736cae8d0bc7/go.mod h1:WkUxfS2JUu3qPo6tRld7ISb8HiC0gVSU91kooBMDVok=
 github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
 github.com/ianlancetaylor/demangle v0.0.0-20200824232613-28f6c0f3b639/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=
 github.com/jackc/chunkreader v1.0.0/go.mod h1:RT6O25fNZIuasFJRyZ4R/Y2BbhasbmZXF9QQ7T3kePo=
@@ -306,6 +311,8 @@ github.com/pashagolub/pgxmock v1.8.0 h1:05JB+jng7yPdeC6i04i8TC4H1Kr7TfcFeQyf4JP6
 github.com/pashagolub/pgxmock v1.8.0/go.mod h1:kDkER7/KJdD3HQjNvFw5siwR7yREKmMvwf8VhAgTK5o=
 github.com/patrickmn/go-cache v2.1.0+incompatible h1:HRMgzkcYKYpi3C8ajMPV8OFXaaRUnok+kx1WdO15EQc=
 github.com/patrickmn/go-cache v2.1.0+incompatible/go.mod h1:3Qf8kWWT7OJRJbdiICTKqZju1ZixQ/KpMGzzAfe6+WQ=
+github.com/pdfcpu/pdfcpu v0.3.13 h1:VFon2Yo1PJt+sA57vPAeXWGLSZ7Ux3Jl4h02M0+s3dg=
+github.com/pdfcpu/pdfcpu v0.3.13/go.mod h1:UJc5xsXg0fpmjp1zOPdyYcAQArc/Zf3V0nv5URe+9fg=
 github.com/pelletier/go-toml v1.9.5 h1:4yBQzkHv+7BHq2PQUZF3Mx0IYxG7LsP222s7Agd3ve8=
 github.com/pelletier/go-toml v1.9.5/go.mod h1:u1nR/EPcESfeI/szUZKdtJ0xRNbUoANCkoOuaOx1Y+c=
 github.com/pelletier/go-toml/v2 v2.0.5 h1:ipoSadvV8oGUjnUbMub59IDPPwfxF694nG/jwbMiyQg=
@@ -442,8 +449,10 @@ golang.org/x/exp/typeparams v0.0.0-20220722155223-a9213eeb770e h1:7Xs2YCOpMlNqSQ
 golang.org/x/exp/typeparams v0.0.0-20220722155223-a9213eeb770e/go.mod h1:AbB0pIl9nAr9wVwH+Z2ZpaocVmF5I4GyWCDIsVjR0bk=
 golang.org/x/image v0.0.0-20190227222117-0694c2d4d067/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190802002840-cff245a6509b/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
-golang.org/x/image v0.0.0-20200927104501-e162460cd6b5 h1:QelT11PB4FXiDEXucrfNckHoFxwt8USGY1ajP1ZF5lM=
+golang.org/x/image v0.0.0-20190823064033-3a9bac650e44/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/image v0.0.0-20200927104501-e162460cd6b5/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
+golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb h1:fqpd0EBDzlHRCjiphRR5Zo/RSWWQlWv34418dnEixWk=
+golang.org/x/image v0.0.0-20210220032944-ac19c3e999fb/go.mod h1:FeLwcggjj3mMvU+oOTbSwawSJRM1uh48EjtB4UJZlP0=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
 golang.org/x/lint v0.0.0-20190301231843-5614ed5bae6f/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=

internal/resolvers/default/link_loader.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/Chatterino/api/internal/logger"
 	"github.com/Chatterino/api/internal/staticresponse"
 	"github.com/Chatterino/api/pkg/cache"
 	"github.com/Chatterino/api/pkg/resolver"
@@ -21,9 +22,10 @@ import (
 )
 
 type LinkLoader struct {
-	baseURL          string
-	customResolvers  []resolver.Resolver
-	maxContentLength uint64
+	baseURL              string
+	customResolvers      []resolver.Resolver
+	contentTypeResolvers []ContentTypeResolver
+	maxContentLength     uint64
 }
 
 func (l *LinkLoader) defaultTooltipData(doc *goquery.Document, r *http.Request, resp *http.Response) tooltipData {
@@ -39,6 +41,8 @@ func (l *LinkLoader) defaultTooltipData(doc *goquery.Document, r *http.Request,
 }
 
 func (l *LinkLoader) Load(ctx context.Context, urlString string, r *http.Request) ([]byte, *int, *string, time.Duration, error) {
+	log := logger.FromContext(ctx)
+
 	requestUrl, err := url.Parse(urlString)
 	if err != nil {
 		return resolver.ReturnInvalidURL()
@@ -91,8 +95,28 @@ func (l *LinkLoader) Load(ctx context.Context, urlString string, r *http.Request
 		return staticresponse.SNoLinkInfoFound.Return()
 	}
 
-	limiter := &resolver.WriteLimiter{Limit: l.maxContentLength}
+	contentType := resp.Header.Get("Content-Type")
+	for _, ctResolver := range l.contentTypeResolvers {
+		if ctResolver.Check(ctx, contentType) {
+			ttResponse, err := ctResolver.Run(ctx, r, resp)
+			if err != nil {
+				log.Errorw("error running ContentTypeResolver",
+					"resolver", ctResolver.Name(),
+					"err", err,
+				)
+
+				return utils.MarshalNoDur(&resolver.Response{
+					Status:  http.StatusInternalServerError,
+					Message: "ContentTypeResolver error " + resolver.CleanResponse(err.Error()),
+				})
+			}
 
+			return utils.MarshalNoDur(ttResponse)
+		}
+	}
+
+	// Fallback to parsing via goquery
+	limiter := &resolver.WriteLimiter{Limit: l.maxContentLength}
 	doc, err := goquery.NewDocumentFromReader(io.TeeReader(resp.Body, limiter))
 	if err != nil {
 		return utils.MarshalNoDur(&resolver.Response{
@@ -124,7 +148,7 @@ func (l *LinkLoader) Load(ctx context.Context, urlString string, r *http.Request
 		Thumbnail: data.ImageSrc,
 	}
 
-	if thumbnail.IsSupportedThumbnailType(resp.Header.Get("content-type")) {
+	if thumbnail.IsSupportedThumbnailType(contentType) {
 		response.Thumbnail = utils.FormatThumbnailURL(l.baseURL, r, resp.Request.URL.String())
 	}
 

internal/resolvers/default/link_resolver.go

@@ -227,10 +227,14 @@ func New(ctx context.Context, cfg config.APIConfig, pool db.Pool, helixClient *h
 	youtube.Initialize(ctx, cfg, pool, &customResolvers)
 	seventv.Initialize(ctx, cfg, pool, &customResolvers)
 
+	contentTypeResolvers := []ContentTypeResolver{}
+	contentTypeResolvers = append(contentTypeResolvers, NewPDFResolver(cfg.BaseURL, cfg.MaxContentLength))
+
 	linkLoader := &LinkLoader{
-		baseURL:          cfg.BaseURL,
-		maxContentLength: cfg.MaxContentLength,
-		customResolvers:  customResolvers,
+		baseURL:              cfg.BaseURL,
+		maxContentLength:     cfg.MaxContentLength,
+		customResolvers:      customResolvers,
+		contentTypeResolvers: contentTypeResolvers,
 	}
 	thumbnailLoader := &ThumbnailLoader{
 		baseURL:          cfg.BaseURL,

internal/resolvers/default/model.go

@@ -1,11 +1,20 @@
 package defaultresolver
 
 import (
+	"context"
 	"html"
+	"net/http"
 
 	"github.com/Chatterino/api/pkg/humanize"
+	"github.com/Chatterino/api/pkg/resolver"
 )
 
+type ContentTypeResolver interface {
+	Check(ctx context.Context, contentType string) bool
+	Run(ctx context.Context, req *http.Request, resp *http.Response) (*resolver.Response, error)
+	Name() string
+}
+
 type tooltipData struct {
 	URL         string
 	Title       string

internal/resolvers/default/pdf_resolver.go

@@ -0,0 +1,110 @@
+package defaultresolver
+
+import (
+	"bytes"
+	"context"
+	"html"
+	"html/template"
+	"io"
+	"net/http"
+	"net/url"
+
+	"github.com/Chatterino/api/internal/logger"
+	"github.com/Chatterino/api/pkg/humanize"
+	"github.com/Chatterino/api/pkg/resolver"
+	"github.com/Chatterino/api/pkg/utils"
+	"github.com/pdfcpu/pdfcpu/pkg/api"
+	"github.com/pdfcpu/pdfcpu/pkg/pdfcpu"
+	"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/validate"
+)
+
+const templateString = `<div style="text-align: left;">
+<b>PDF File</b><br>
+{{if .Title}}<b>Title:</b> {{.Title}}<br>{{end}}
+{{if .Author}}<b>Author:</b> {{.Author}}<br>{{end}}
+<span style="color: #808892;">
+{{.PageCount}} pages{{if .CreationDate}}&nbsp;•&nbsp;{{.CreationDate}}{{end}}
+</span>
+</div>
+`
+
+var pdfTooltipTemplate = template.Must(template.New("pdfTooltipTemplate").Parse(templateString))
+
+type pdfTooltipData struct {
+	Title        string
+	Author       string
+	PageCount    int
+	CreationDate string
+}
+
+type PDFResolver struct {
+	baseURL          string
+	maxContentLength uint64
+}
+
+func (r *PDFResolver) Check(ctx context.Context, contentType string) bool {
+	return contentType == "application/pdf"
+}
+
+func (r *PDFResolver) Run(ctx context.Context, req *http.Request, resp *http.Response) (*resolver.Response, error) {
+	log := logger.FromContext(ctx)
+
+	limiter := resolver.WriteLimiter{Limit: r.maxContentLength}
+	limitedReader := io.TeeReader(resp.Body, &limiter)
+	buffer, err := io.ReadAll(limitedReader)
+	if err != nil {
+		log.Errorw("error reading response body", "err", err)
+		return nil, err
+	}
+
+	readSeeker := bytes.NewReader(buffer)
+
+	pdfCtx, err := api.ReadContext(readSeeker, pdfcpu.NewDefaultConfiguration())
+	if err != nil {
+		log.Errorw("error reading pdf context", "err", err)
+		return nil, err
+	}
+
+	if err = validate.XRefTable(pdfCtx.XRefTable); err != nil {
+		log.Errorw("error validating XRefTable", "err", err)
+		return nil, err
+	}
+
+	dtString := ""
+	if creationDt, ok := pdfcpu.DateTime(pdfCtx.CreationDate, true); ok {
+		dtString = humanize.CreationDate(creationDt)
+	}
+
+	ttData := pdfTooltipData{
+		Title:        html.EscapeString(humanize.Title(pdfCtx.Title)),
+		Author:       html.EscapeString(humanize.Title(pdfCtx.Author)),
+		PageCount:    pdfCtx.PageCount,
+		CreationDate: dtString,
+	}
+
+	var tooltip bytes.Buffer
+	if err := pdfTooltipTemplate.Execute(&tooltip, ttData); err != nil {
+		return nil, err
+	}
+
+	targetURL := resp.Request.URL.String()
+	response := &resolver.Response{
+		Status:    http.StatusOK,
+		Link:      targetURL,
+		Tooltip:   url.PathEscape(tooltip.String()),
+		Thumbnail: utils.FormatThumbnailURL(r.baseURL, req, targetURL),
+	}
+
+	return response, nil
+}
+
+func (r *PDFResolver) Name() string {
+	return "PDFResolver"
+}
+
+func NewPDFResolver(baseURL string, maxContentLength uint64) *PDFResolver {
+	return &PDFResolver{
+		baseURL:          baseURL,
+		maxContentLength: maxContentLength,
+	}
+}

pkg/thumbnail/thumbnail.go

@@ -10,8 +10,10 @@ import (
 )
 
 var (
-	supportedThumbnails = []string{"image/jpeg", "image/png", "image/gif", "image/webp"}
-	animatedThumbnails  = []string{"image/gif", "image/webp"}
+	supportedThumbnails = []string{
+		"image/jpeg", "image/png", "image/gif", "image/webp", "application/pdf",
+	}
+	animatedThumbnails = []string{"image/gif", "image/webp"}
 
 	cfg config.APIConfig
 )
@@ -58,7 +60,14 @@ func BuildStaticThumbnail(inputBuf []byte, resp *http.Response) ([]byte, error)
 		return []byte{}, fmt.Errorf("could not transform image from url: %s", resp.Request.URL)
 	}
 
-	outputBuf, _, err := image.ExportNative()
+	var outputBuf []byte
+	if image.Format() == vips.ImageTypePDF {
+		// Export thumbnails for PDF as PNG
+		outputBuf, _, err = image.ExportPng(vips.NewPngExportParams())
+	} else {
+		outputBuf, _, err = image.ExportNative()
+	}
+
 	if err != nil {
 		return []byte{}, fmt.Errorf("could not export image from url: %s", resp.Request.URL)
 	}