Implemented cookie handling to store some of the state

README.md

@@ -73,10 +73,12 @@ local Lixie instance which probably does not exist.
 
 - Properly vendor static resources (bootstrap CSS, htmx JS)
 
-- convert viewing preferences to be tracked via cookie
- - FTS filter: global
++ convert viewing preferences to be tracked via cookie
+ - FTS filter: global (partially implemented)
  - others: per-view
 
+- identify better logging pattern
+
 ## Prettiness
 
 - favicon

cm/README.md

@@ -0,0 +1,26 @@
+# Cookie Monster #
+
+This sublibrary (someday perhaps available separately, but for now, not) is
+convenience wrapper for handling client state in client (fully in the
+cookie). For now, the state is not encrypted at all (although we could), as
+I do not really see the point. The idea is not to store secrets using this,
+just e.g. state in various views so that the client resumes same state
+implicitly when they go back to a view.
+
+## Short form
+
+```
+err = monster.Run(r, w, &state)
+```
+
+Where
+```
+r = http.Request
+w = http.ResponseWriter
+state = arbitrary struct (ideally empty)
+```
+
+The struct is examined through reflection and `cm:"field"` entries are
+CRUDed based on `"field"` in the `http.Request`. Note that json definitions
+must be also supplied for the fields, or otherwise they will not be
+imported/exported.

cm/cm.go

@@ -0,0 +1,55 @@
+/*
+ * Author: Markus Stenberg <[email protected]>
+ *
+ * Copyright (c) 2024 Markus Stenberg
+ *
+ * Created:       Fri Apr 26 10:35:46 2024 mstenber
+ * Last modified: Fri Apr 26 14:38:05 2024 mstenber
+ * Edit time:     93 min
+ *
+ */
+
+package cm
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"reflect"
+)
+
+type CookieSource interface {
+	Cookie(string) (*http.Cookie, error)
+}
+
+var ErrNoSource = errors.New("specified cookie source is nil")
+
+func cookieName(state any) (string, error) {
+	v := reflect.ValueOf(state)
+	if v.Kind() != reflect.Pointer {
+		return "", fmt.Errorf("Invalid kind: %s", v.Kind())
+	}
+
+	s := v.Elem()
+	if s.Kind() != reflect.Struct {
+		return "", fmt.Errorf("Invalid kind pointer: %s", s.Kind())
+	}
+	return fmt.Sprintf("cm-%s", s.Type()), nil
+}
+
+func Run(r *http.Request, w http.ResponseWriter, state any) error {
+	err := r.ParseForm()
+	if err != nil {
+		return err
+	}
+
+	changed, err := Parse(r, URLWrapper(r.Form), state)
+	if err != nil {
+		return err
+	}
+	if changed {
+		fmt.Printf("XXX changed\n")
+		return Write(w, state)
+	}
+	return nil
+}

cm/cm_test.go

@@ -0,0 +1,124 @@
+/*
+ * Author: Markus Stenberg <[email protected]>
+ *
+ * Copyright (c) 2024 Markus Stenberg
+ *
+ * Created:       Fri Apr 26 10:44:18 2024 mstenber
+ * Last modified: Fri Apr 26 14:39:52 2024 mstenber
+ * Edit time:     40 min
+ *
+ */
+
+package cm
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+type empty struct {
+}
+
+type tt struct {
+	B  bool   `json:"b" cm:"bf"`
+	I  int64  `json:"i" cm:"if"`
+	II int    `json:"ii" cm:"iif"`
+	S  string `json:"s" cm:"sf"`
+	U  uint64 `json:"u" cm:"uf"`
+}
+
+type staticCookie struct {
+	// FormValued interface provider
+	URLWrapper
+
+	// Data for rest of CookieSource
+	name   string
+	cookie *http.Cookie
+	err    error
+}
+
+func (self *staticCookie) Cookie(name string) (*http.Cookie, error) {
+	if name != self.name {
+		return nil, fmt.Errorf("Invalid name: %s <> %s", name, self.name)
+	}
+	if self.cookie == nil {
+		return nil, http.ErrNoCookie
+	}
+	return self.cookie, self.err
+}
+
+func TestParse(t *testing.T) {
+	// first off, ensure the type checking is correct. anything
+	// else than pointer (to a struct) shouldn't work
+	_, err := Parse(nil, nil, nil)
+	assert.Assert(t, err != nil)
+
+	es := empty{}
+	_, err = Parse(nil, nil, es)
+	assert.Assert(t, err != nil)
+
+	i := 42
+	_, err = Parse(nil, nil, &i)
+	assert.Assert(t, err != nil)
+
+	// nil pointer is still error
+	_, err = Parse(nil, nil, &es)
+	assert.Equal(t, err, ErrNoSource)
+
+	// empty is fine but doesn't do anything yet
+	sc1 := staticCookie{name: "cm-cm.empty"}
+	changed, err := Parse(&sc1, sc1.URLWrapper, &es)
+	assert.Equal(t, err, nil)
+	assert.Equal(t, changed, false)
+
+	q1, err := ToQueryString("x", &sc1)
+	assert.Equal(t, err, nil)
+	assert.Equal(t, q1, "x")
+
+	ts := tt{}
+	sc2 := staticCookie{name: "cm-cm.tt"}
+	changed, err = Parse(&sc2, sc2.URLWrapper, &ts)
+	assert.Equal(t, err, nil)
+	assert.Equal(t, changed, false)
+
+	sc3 := staticCookie{name: "cm-cm.tt", URLWrapper: URLWrapper(url.Values{
+		"bf":  []string{"true"},
+		"if":  []string{"-1"},
+		"sf":  []string{"str"},
+		"iif": []string{"7"},
+		"uf":  []string{"42"},
+	})}
+	assert.Equal(t, sc3.FormValue("bf"), "true")
+	changed, err = Parse(&sc3, sc3.URLWrapper, &ts)
+	assert.Equal(t, err, nil)
+	assert.Equal(t, changed, true)
+	assert.Equal(t, ts.B, true)
+	assert.Equal(t, ts.I, int64(-1))
+	assert.Equal(t, ts.U, uint64(42))
+
+	q3, err := ToQueryString("x", &ts)
+	assert.Equal(t, err, nil)
+	assert.Equal(t, q3, "x?bf=true&if=-1&iif=7&sf=str&uf=42")
+
+	// Export the cookie
+	cookie, err := ToCookie(&ts)
+	assert.Equal(t, err, nil)
+	assert.Assert(t, cookie != nil)
+
+	// Pretend we're new request: take in the cookie
+	sc4 := staticCookie{name: "cm-cm.tt", cookie: cookie, err: nil}
+	ts4 := tt{}
+	fmt.Printf("!!!\n")
+	changed, err = Parse(&sc4, sc4.URLWrapper, &ts4)
+	assert.Equal(t, changed, false)
+	assert.Equal(t, err, nil)
+
+	// The resulting query string (=~ content) should be same
+	q4, err := ToQueryString("x", &ts4)
+	assert.Equal(t, err, nil)
+	assert.Equal(t, q3, q4)
+}

form.go → cm/form.go

@@ -5,33 +5,45 @@
  *
  */
 
-package main
+package cm
 
 import "strconv"
 
 type FormValued interface {
 	FormValue(string) string
 }
 
-func intFromForm(r FormValued, key string, value *int) (found bool, err error) {
+func IntFromForm(r FormValued, key string, value *int) (found bool, err error) {
 	raw := r.FormValue(key)
 	if raw == "" {
 		return
 	}
+	found = true
 	*value, err = strconv.Atoi(raw)
 	return
 }
 
-func uint64FromForm(r FormValued, key string, value *uint64) (found bool, err error) {
+func Int64FromForm(r FormValued, key string, value *int64) (found bool, err error) {
 	raw := r.FormValue(key)
 	if raw == "" {
 		return
 	}
+	found = true
+	*value, err = strconv.ParseInt(raw, 10, 64)
+	return
+}
+
+func Uint64FromForm(r FormValued, key string, value *uint64) (found bool, err error) {
+	raw := r.FormValue(key)
+	if raw == "" {
+		return
+	}
+	found = true
 	*value, err = strconv.ParseUint(raw, 10, 64)
 	return
 }
 
-func boolFromForm(r FormValued, key string, value *bool) {
+func BoolFromForm(r FormValued, key string, value *bool) {
 	raw := r.FormValue(key)
 	if raw == "" {
 		return

cm/parse.go

@@ -0,0 +1,122 @@
+/*
+ * Author: Markus Stenberg <[email protected]>
+ *
+ * Copyright (c) 2024 Markus Stenberg
+ *
+ * Created:       Fri Apr 26 14:09:03 2024 mstenber
+ * Last modified: Fri Apr 26 14:40:37 2024 mstenber
+ * Edit time:     5 min
+ *
+ */
+
+package cm
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"reflect"
+)
+
+func Parse(r CookieSource, u URLWrapper, state any) (changed bool, err error) {
+	if r == nil {
+		err = ErrNoSource
+		return
+	}
+	name, err := cookieName(state)
+	if err != nil {
+		return
+	}
+
+	// Handle the cookie, if any
+	cookie, err := r.Cookie(name)
+	switch {
+	case err == http.ErrNoCookie:
+		// fmt.Printf("Cookie not found\n")
+		err = nil
+	case err != nil:
+		// fmt.Printf("Failed to get cookie: %s", err)
+		return
+	case cookie != nil:
+		err = cookie.Valid()
+		if err != nil {
+			return
+		}
+		data, err := base64.StdEncoding.DecodeString(cookie.Value)
+		if err != nil {
+			return false, err
+		}
+		err = json.Unmarshal(data, state)
+		if err != nil {
+			return false, err
+		}
+	}
+
+	// Struct we're filling from the form
+	s := reflect.ValueOf(state).Elem()
+
+	// Go through the fields and fill in the values IF they differ from what is in the struct
+	for _, field := range reflect.VisibleFields(s.Type()) {
+		formKey := field.Tag.Get("cm")
+		if formKey == "" {
+			continue
+		}
+		if !u.HasValue(formKey) {
+			continue
+		}
+
+		value := u.FormValue(formKey)
+
+		f := s.FieldByName(field.Name)
+		if !(f.IsValid() && f.CanSet()) {
+			err = fmt.Errorf("invalid field %s", field.Name)
+			return
+		}
+
+		kind := field.Type.Kind()
+		switch {
+		case kind == reflect.String:
+			if f.String() != value {
+				f.SetString(value)
+				changed = true
+			}
+		case kind == reflect.Bool:
+			var b bool
+			BoolFromForm(u, formKey, &b)
+			if f.Bool() != b {
+				f.SetBool(b)
+				changed = true
+			}
+
+		case f.CanInt():
+			var i int64
+			_, err = Int64FromForm(u, formKey, &i)
+			if err != nil {
+				return
+			}
+			if f.Int() != i {
+				f.SetInt(i)
+				changed = true
+			}
+
+		case f.CanUint():
+			var uv uint64
+			_, err = Uint64FromForm(u, formKey, &uv)
+			if err != nil {
+				return
+			}
+			if f.Uint() != uv {
+				f.SetUint(uv)
+				changed = true
+			}
+		default:
+			err = fmt.Errorf("insupported field %s kind: %s", field.Name, kind)
+		}
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}