[chore] much improved paging package (#2182)

internal/paging/parse.go

@@ -0,0 +1,111 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package paging
+
+import (
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+)
+
+// ParseIDPage parses an ID Page from a request context, returning BadRequest on error parsing.
+// The min, max and default parameters define the page size limit minimum, maximum and default
+// value, where a non-zero default will enforce paging for the endpoint on which this is called.
+// While conversely, a zero default limit will not enforce paging, returning a nil page value.
+func ParseIDPage(c *gin.Context, min, max, _default int) (*Page, gtserror.WithCode) {
+	// Extract request query params.
+	sinceID := c.Query("since_id")
+	minID := c.Query("min_id")
+	maxID := c.Query("max_id")
+
+	// Extract request limit parameter.
+	limit, errWithCode := ParseLimit(c, min, max, _default)
+	if errWithCode != nil {
+		return nil, errWithCode
+	}
+
+	if sinceID == "" &&
+		minID == "" &&
+		maxID == "" &&
+		limit == 0 {
+		// No ID paging params provided, and no default
+		// limit value which indicates paging not enforced.
+		return nil, nil
+	}
+
+	return &Page{
+		Min:   MinID(minID, sinceID),
+		Max:   MaxID(maxID),
+		Limit: limit,
+	}, nil
+}
+
+// ParseShortcodeDomainPage parses an emoji shortcode domain Page from a request context, returning BadRequest
+// on error parsing. The min, max and default parameters define the page size limit minimum, maximum and default
+// value where a non-zero default will enforce paging for the endpoint on which this is called. While conversely,
+// a zero default limit will not enforce paging, returning a nil page value.
+func ParseShortcodeDomainPage(c *gin.Context, min, max, _default int) (*Page, gtserror.WithCode) {
+	// Extract request query parameters.
+	minShortcode := c.Query("min_shortcode_domain")
+	maxShortcode := c.Query("max_shortcode_domain")
+
+	// Extract request limit parameter.
+	limit, errWithCode := ParseLimit(c, min, max, _default)
+	if errWithCode != nil {
+		return nil, errWithCode
+	}
+
+	if minShortcode == "" &&
+		maxShortcode == "" &&
+		limit == 0 {
+		// No ID paging params provided, and no default
+		// limit value which indicates paging not enforced.
+		return nil, nil
+	}
+
+	return &Page{
+		Min:   MinShortcodeDomain(minShortcode),
+		Max:   MaxShortcodeDomain(maxShortcode),
+		Limit: limit,
+	}, nil
+}
+
+// ParseLimit parses the limit query parameter from a request context, returning BadRequest on error parsing and _default if zero limit given.
+func ParseLimit(c *gin.Context, min, max, _default int) (int, gtserror.WithCode) {
+	// Get limit query param.
+	str := c.Query("limit")
+
+	// Attempt to parse limit int.
+	i, err := strconv.Atoi(str)
+	if err != nil {
+		const help = "bad integer limit value"
+		return 0, gtserror.NewErrorBadRequest(err, help)
+	}
+
+	switch {
+	case i == 0:
+		return _default, nil
+	case i < min:
+		return min, nil
+	case i > max:
+		return max, nil
+	default:
+		return i, nil
+	}
+}