ipfs-search/ipfs-search

package tika

import (
    "context"
    "encoding/json"
    "fmt"
    "log"
    "net/url"

    "github.com/ipfs-search/ipfs-search/components/extractor"
    "github.com/ipfs-search/ipfs-search/components/protocol"
    "github.com/ipfs-search/ipfs-search/instr"
    t "github.com/ipfs-search/ipfs-search/types"
    "github.com/ipfs-search/ipfs-search/utils"
)

// Extractor extracts metadata using the ipfs-tika server.
type Extractor struct {
    config   *Config
    getter   utils.HTTPBodyGetter
    protocol protocol.Protocol

    *instr.Instrumentation
}

func (e *Extractor) getExtractURL(r *t.AnnotatedResource) string {
    gwURL := e.protocol.GatewayURL(r)
    return fmt.Sprintf("%s/extract?url=%s", e.config.TikaExtractorURL, url.QueryEscape(gwURL))
}

// Extract metadata from a (potentially) referenced resource, updating
// Metadata or returning an error.
func (e *Extractor) Extract(ctx context.Context, r *t.AnnotatedResource, m interface{}) error {
    ctx, span := e.Tracer.Start(ctx, "extractor.tika.Extract")
    defer span.End()

    if err := extractor.ValidateMaxSize(ctx, r, e.config.MaxFileSize); err != nil {
        return err
    }

    // Timeout if extraction hasn't fully completed within this time.
    ctx, cancel := context.WithTimeout(ctx, e.config.RequestTimeout)
    defer cancel()

    body, err := e.getter.GetBody(ctx, e.getExtractURL(r), 200)
    if err != nil {
        return err
    }
    defer body.Close()

    // Parse resulting JSON
    if err := json.NewDecoder(body).Decode(m); err != nil {
        err := fmt.Errorf("%w: %v", t.ErrUnexpectedResponse, err)
        span.RecordError(err)
        return err
    }

    log.Printf("Got tika metadata metadata for '%v'", r)

    return nil
}

// New returns a new Tika extractor.
func New(config *Config, getter utils.HTTPBodyGetter, protocol protocol.Protocol, instr *instr.Instrumentation) extractor.Extractor {
    return &Extractor{
        config,
        getter,
        protocol,
        instr,
    }
}

// Compile-time assurance that implementation satisfies interface.
var _ extractor.Extractor = &Extractor{}