cmd/pkgserver: add get endpoint

cmd/pkgserver/api.go

@@ -2,6 +2,8 @@ package main
 
 import (
 	"bytes"
+	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"path"
@@ -53,7 +55,58 @@ func serveStatus(index *PackageIndex) func(w http.ResponseWriter, r *http.Reques
 	}
 }
 
+type GetPayload struct {
+	Count  int                 `json:"count"`
+	Values []PackageIndexEntry `json:"values"`
+}
+
+func NewGetPayload(values []*PackageIndexEntry) GetPayload {
+	count := len(values)
+	v := make([]PackageIndexEntry, count)
+	for i, _ := range values {
+		v[i] = *values[i]
+	}
+	return GetPayload{
+		Count:  count,
+		Values: v,
+	}
+}
+
+func serveGet(index *PackageIndex) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		q := r.URL.Query()
+		limit, err := strconv.Atoi(q.Get("limit"))
+		if err != nil || limit > 100 || limit < 1 {
+			http.Error(w, fmt.Sprintf("limit must be an integer between 1 and 100"), http.StatusBadRequest)
+			return
+		}
+		i, err := strconv.Atoi(q.Get("index"))
+		if err != nil || i >= len(index.sorts[0]) || i < 0 {
+			http.Error(w, fmt.Sprintf("index must be an integer between 0 and %d", len(index.sorts[0])-1), http.StatusBadRequest)
+			return
+		}
+		sort, err := strconv.Atoi(q.Get("sort"))
+		if err != nil || sort >= len(index.sorts) || sort < 0 {
+			http.Error(w, fmt.Sprintf("sort must be an integer between 0 and %d", len(index.sorts)-1), http.StatusBadRequest)
+			return
+		}
+		values := index.sorts[sort][i:min(i+limit, len(index.sorts[sort]))]
+		payload := NewGetPayload(values)
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		w.Header().Set("Cache-Control", "no-cache, no-store, must-revalidate")
+		w.WriteHeader(http.StatusOK)
+		b, err := json.Marshal(payload)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+		_, err = bytes.NewBuffer(b).WriteTo(w)
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+	}
+}
 func apiRoutes(index *PackageIndex) {
 	http.HandleFunc("GET /api/count", serveCount(index))
+	http.HandleFunc("GET /api/get", serveGet(index))
 	http.HandleFunc("GET /api/status/", serveStatus(index))
 }