Add route for querying signing_info for all validators (#3952)

Also remove duplicate pagination:
- move function to extract query params into types/rest
- adjust pagination values locally until available in tendermint for validators

Code cleanup:
- helper function in test
- fix pagination description in swagger.yaml
- uint instead of int when possible

Closes: #3226
Closes: #3991

types/rest/rest.go

@@ -3,9 +3,12 @@
 package rest
 
 import (
+	"errors"
 	"fmt"
+	"github.com/tendermint/tendermint/types"
 	"io/ioutil"
 	"net/http"
+	"net/url"
 	"strconv"
 	"strings"
 
@@ -13,6 +16,11 @@ import (
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
+const (
+	DefaultPage  = 1
+	DefaultLimit = 30 // should be consistent with tendermint/tendermint/rpc/core/pipe.go:19
+)
+
 // GasEstimateResponse defines a response definition for tx gas estimation.
 type GasEstimateResponse struct {
 	GasEstimate uint64 `json:"gas_estimate"`
@@ -211,3 +219,53 @@ func PostProcessResponse(w http.ResponseWriter, cdc *codec.Codec, response inter
 	w.Header().Set("Content-Type", "application/json")
 	_, _ = w.Write(output)
 }
+
+// ParseHTTPArgs parses the request's URL and returns a slice containing all arguments pairs.
+// It separates page and limit used for pagination
+func ParseHTTPArgs(r *http.Request) (tags []string, page, limit int, err error) {
+	tags = make([]string, 0, len(r.Form))
+	for key, values := range r.Form {
+		if key == "page" || key == "limit" {
+			continue
+		}
+		var value string
+		value, err = url.QueryUnescape(values[0])
+		if err != nil {
+			return tags, page, limit, err
+		}
+
+		var tag string
+		if key == types.TxHeightKey {
+			tag = fmt.Sprintf("%s=%s", key, value)
+		} else {
+			tag = fmt.Sprintf("%s='%s'", key, value)
+		}
+		tags = append(tags, tag)
+	}
+
+	pageStr := r.FormValue("page")
+	if pageStr == "" {
+		page = DefaultPage
+	} else {
+		page, err = strconv.Atoi(pageStr)
+		if err != nil {
+			return tags, page, limit, err
+		} else if page <= 0 {
+			return tags, page, limit, errors.New("page must greater than 0")
+		}
+	}
+
+	limitStr := r.FormValue("limit")
+	if limitStr == "" {
+		limit = DefaultLimit
+	} else {
+		limit, err = strconv.Atoi(limitStr)
+		if err != nil {
+			return tags, page, limit, err
+		} else if limit <= 0 {
+			return tags, page, limit, errors.New("limit must greater than 0")
+		}
+	}
+
+	return tags, page, limit, nil
+}

types/rest/rest_test.go

@@ -3,6 +3,7 @@
 package rest
 
 import (
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -55,3 +56,55 @@ func TestBaseReqValidateBasic(t *testing.T) {
 		})
 	}
 }
+
+func TestParseHTTPArgs(t *testing.T) {
+	req0 := mustNewRequest(t, "", "/", nil)
+	req1 := mustNewRequest(t, "", "/?limit=5", nil)
+	req2 := mustNewRequest(t, "", "/?page=5", nil)
+	req3 := mustNewRequest(t, "", "/?page=5&limit=5", nil)
+
+	reqE1 := mustNewRequest(t, "", "/?page=-1", nil)
+	reqE2 := mustNewRequest(t, "", "/?limit=-1", nil)
+	req4 := mustNewRequest(t, "", "/?foo=faa", nil)
+
+	tests := []struct {
+		name  string
+		req   *http.Request
+		w     http.ResponseWriter
+		tags  []string
+		page  int
+		limit int
+		err   bool
+	}{
+		{"no params", req0, httptest.NewRecorder(), []string{}, DefaultPage, DefaultLimit, false},
+		{"Limit", req1, httptest.NewRecorder(), []string{}, DefaultPage, 5, false},
+		{"Page", req2, httptest.NewRecorder(), []string{}, 5, DefaultLimit, false},
+		{"Page and limit", req3, httptest.NewRecorder(), []string{}, 5, 5, false},
+
+		{"error page 0", reqE1, httptest.NewRecorder(), []string{}, DefaultPage, DefaultLimit, true},
+		{"error limit 0", reqE2, httptest.NewRecorder(), []string{}, DefaultPage, DefaultLimit, true},
+
+		{"tags", req4, httptest.NewRecorder(), []string{"foo='faa'"}, DefaultPage, DefaultLimit, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tags, page, limit, err := ParseHTTPArgs(tt.req)
+			if tt.err {
+				require.NotNil(t, err)
+			} else {
+				require.Nil(t, err)
+				require.Equal(t, tt.tags, tags)
+				require.Equal(t, tt.page, page)
+				require.Equal(t, tt.limit, limit)
+			}
+		})
+	}
+}
+
+func mustNewRequest(t *testing.T, method, url string, body io.Reader) *http.Request {
+	req, err := http.NewRequest(method, url, body)
+	require.NoError(t, err)
+	err = req.ParseForm()
+	require.NoError(t, err)
+	return req
+}