Improve API for the web UI

pkg/api/criterion.go

@@ -0,0 +1,102 @@
+package api
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+)
+
+const (
+	defaultPerPage = 100
+	defaultPage    = 1
+)
+
+const nextPageHeader = "X-Next-Page"
+
+type pageInfo struct {
+	startIndex int
+	endIndex   int
+	nextPage   int
+}
+
+type searchCriterion struct {
+	Search string `url:"search"`
+	Status string `url:"status"`
+}
+
+func newSearchCriterion(query url.Values) *searchCriterion {
+	if len(query) == 0 {
+		return nil
+	}
+
+	search := query.Get("search")
+	status := query.Get("status")
+
+	if status == "" && search == "" {
+		return nil
+	}
+
+	return &searchCriterion{Search: search, Status: status}
+}
+
+func (c *searchCriterion) withStatus(name string) bool {
+	return c.Status == "" || strings.EqualFold(name, c.Status)
+}
+
+func (c *searchCriterion) searchIn(values ...string) bool {
+	if c.Search == "" {
+		return true
+	}
+
+	for _, v := range values {
+		if strings.Contains(strings.ToLower(v), strings.ToLower(c.Search)) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func pagination(request *http.Request, max int) (pageInfo, error) {
+	perPage, err := getIntParam(request, "per_page", defaultPerPage)
+	if err != nil {
+		return pageInfo{}, err
+	}
+
+	page, err := getIntParam(request, "page", defaultPage)
+	if err != nil {
+		return pageInfo{}, err
+	}
+
+	startIndex := (page - 1) * perPage
+	if startIndex != 0 && startIndex >= max {
+		return pageInfo{}, fmt.Errorf("invalid request: page: %d, per_page: %d", page, perPage)
+	}
+
+	endIndex := startIndex + perPage
+	if endIndex >= max {
+		endIndex = max
+	}
+
+	nextPage := 1
+	if page*perPage < max {
+		nextPage = page + 1
+	}
+
+	return pageInfo{startIndex: startIndex, endIndex: endIndex, nextPage: nextPage}, nil
+}
+
+func getIntParam(request *http.Request, key string, defaultValue int) (int, error) {
+	raw := request.URL.Query().Get(key)
+	if raw == "" {
+		return defaultValue, nil
+	}
+
+	value, err := strconv.Atoi(raw)
+	if err != nil || value <= 0 {
+		return 0, fmt.Errorf("invalid request: %s: %d", key, value)
+	}
+	return value, nil
+}