add paging implementation

http/paging.go

@@ -0,0 +1,109 @@
+package http
+
+import (
+	"context"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	"github.com/influxdata/platform"
+)
+
+// decodeFindOptions returns a FindOptions decoded from http request.
+func decodeFindOptions(ctx context.Context, r *http.Request) (*platform.FindOptions, error) {
+	opts := &platform.FindOptions{}
+	qp := r.URL.Query()
+
+	if offset := qp.Get("offset"); offset != "" {
+		o, err := strconv.Atoi(offset)
+		if err != nil {
+			return nil, err
+		}
+
+		opts.Offset = o
+	}
+
+	if limit := qp.Get("limit"); limit != "" {
+		l, err := strconv.Atoi(limit)
+		if err != nil {
+			return nil, err
+		}
+
+		opts.Limit = l
+	}
+
+	if sortBy := qp.Get("sortBy"); sortBy != "" {
+		opts.SortBy = sortBy
+	}
+
+	if descending := qp.Get("descending"); descending != "" {
+		desc, err := strconv.ParseBool(descending)
+		if err != nil {
+			return nil, err
+		}
+
+		opts.Descending = desc
+	}
+
+	return opts, nil
+}
+
+// newPagingLinks returns a PagingLinks.
+// num is the number of returned results.
+func newPagingLinks(basePath string, opts platform.FindOptions, f platform.PagingFilter, num int) *platform.PagingLinks {
+	u := url.URL{
+		Path: basePath,
+	}
+
+	values := url.Values{}
+	for k, vs := range f.QueryParams() {
+		for _, v := range vs {
+			if v != "" {
+				values.Add(k, v)
+			}
+		}
+	}
+
+	var self, next, prev string
+	for k, vs := range opts.QueryParams() {
+		for _, v := range vs {
+			if v != "" {
+				values.Add(k, v)
+			}
+		}
+	}
+
+	u.RawQuery = values.Encode()
+	self = u.String()
+
+	if num >= opts.Limit {
+		nextOffset := opts.Offset + opts.Limit
+		values.Set("offset", strconv.Itoa(nextOffset))
+		u.RawQuery = values.Encode()
+		next = u.String()
+	}
+
+	if opts.Offset > 0 {
+		prevOffset := opts.Offset - opts.Limit
+		if prevOffset < 0 {
+			prevOffset = 0
+		}
+		values.Set("offset", strconv.Itoa(prevOffset))
+		u.RawQuery = values.Encode()
+		prev = u.String()
+	}
+
+	links := &platform.PagingLinks{
+		Self: map[string]string{
+			"self": self,
+		},
+		Prev: map[string]string{
+			"prev": prev,
+		},
+		Next: map[string]string{
+			"next": next,
+		},
+	}
+
+	return links
+}

paging.go

@@ -0,0 +1,38 @@
+package platform
+
+import (
+	"strconv"
+)
+
+// PagingFilter represents a filter containing url query params.
+type PagingFilter interface {
+	// QueryParams returns a map containing url query params.
+	QueryParams() map[string][]string
+}
+
+// PagingLinks represents paging links.
+type PagingLinks struct {
+	Prev map[string]string `json:"prev"`
+	Self map[string]string `json:"self"`
+	Next map[string]string `json:"next"`
+}
+
+// FindOptions represents options passed to all find methods with multiple results.
+type FindOptions struct {
+	Limit      int
+	Offset     int
+	SortBy     string
+	Descending bool
+}
+
+// QueryParams returns a map containing url query params.
+func (f FindOptions) QueryParams() map[string][]string {
+	qp := map[string][]string{
+		"limit":      []string{strconv.Itoa(f.Limit)},
+		"offset":     []string{strconv.Itoa(f.Offset)},
+		"sortBy":     []string{f.SortBy},
+		"descending": []string{strconv.FormatBool(f.Descending)},
+	}
+
+	return qp
+}