Fix sign-in page to show Sign Up link only when sign-up is enabled

docs/plans/2026-08-19-allow-signup-env.md

@@ -0,0 +1,189 @@
+# Env-Var-Controlled Sign-Up Implementation Plan
+
+**Goal:** Gate sign-up and the sign-in "Sign Up" link on the `PODSTALK_ALLOW_SIGNUP` environment variable instead of the number of existing users.
+
+**Architecture:** Add an `AllowSignup bool` field to the `AuthHandler`. `main.go` reads `PODSTALK_ALLOW_SIGNUP` and sets it on the handler. The signup handler and the sign-in page link both consult this boolean. `store.UserCount()` stays as a general utility but is no longer used by authentication.
+
+**Tech Stack:** Go (net/http), `strconv.ParseBool` for env parsing.
+
+---
+
+## File Structure
+
+- Modify: `main.go` — read env var, set `AllowSignup` on the `AuthHandler`.
+- Modify: `handler/auth.go` — replace count-based gating with the `AllowSignup` flag.
+- No changes to `store/store.go` (`UserCount` is left in place).
+- Modify: `template/signin.html` — render the "Sign Up" nav link with `{{if .AllowSignup}}`.
+
+---
+
+### Task 1: Add `AllowSignup` field and switch signup gating
+
+**Files:**
+- Modify: `handler/auth.go`
+
+- [ ] **Step 1: Add the `AllowSignup` field to `AuthHandler` and replace the count-based redirect**
+
+Replace:
+
+```go
+type AuthHandler struct {
+	Store    *store.Store
+	Sessions *SessionStore
+	Tpl      *Templates
+}
+
+func (h *AuthHandler) ServeSignup(w http.ResponseWriter, r *http.Request) {
+	count, err := h.Store.UserCount()
+	if err == nil && count > 0 {
+		http.Redirect(w, r, "/signin", http.StatusSeeOther)
+		return
+	}
+```
+
+with:
+
+```go
+type AuthHandler struct {
+	Store       *store.Store
+	Sessions    *SessionStore
+	Tpl         *Templates
+	AllowSignup bool
+}
+
+func (h *AuthHandler) ServeSignup(w http.ResponseWriter, r *http.Request) {
+	if !h.AllowSignup {
+		http.Redirect(w, r, "/signin", http.StatusSeeOther)
+		return
+	}
+```
+
+- [ ] **Step 2: Replace the `hasUsers()` helper with an `allowSignup()` helper**
+
+Replace:
+
+```go
+func (h *AuthHandler) hasUsers() bool {
+	count, err := h.Store.UserCount()
+	return err == nil && count > 0
+}
+```
+
+with:
+
+```go
+func (h *AuthHandler) allowSignup() bool {
+	return h.AllowSignup
+}
+```
+
+- [ ] **Step 3: Update the three `AllowSignup` template renders to use `allowSignup()`**
+
+Replace every occurrence of `"AllowSignup": h.allowSignup()` where it was passed as the `HasUser` key. In the three render calls in the sign-in handler, ensure the map key is `AllowSignup`:
+
+```go
+map[string]any{"AllowSignup": h.allowSignup()}
+map[string]any{"Error": "Invalid email or password.", "AllowSignup": h.allowSignup()}
+map[string]any{"Error": "Invalid email or password.", "AllowSignup": h.allowSignup()}
+```
+
+- [ ] **Step 3b: Update the sign-in template to use `AllowSignup` without inversion**
+
+In `template/signin.html`, the nav-link conditional must render the link when sign-up is allowed. Replace `{{if not .HasUser}}` with `{{if .AllowSignup}}`. (Retain the `{{end}}`.)
+
+- [ ] **Step 4: Commit**
+
+```bash
+git add handler/auth.go
+git commit -m "Gate sign-up on AllowSignup field instead of user count"
+```
+
+---
+
+### Task 2: Read the env var in `main.go` and wire it up
+
+**Files:**
+- Modify: `main.go`
+
+- [ ] **Step 1: Add `strconv` to imports**
+
+In `main.go`, add `"strconv"` to the import block (after `"os"`).
+
+- [ ] **Step 2: Parse `PODSTALK_ALLOW_SIGNUP` and set it on the handler**
+
+After the existing `baseURL` block, add:
+
+```go
+	allowSignup := false
+	if v := os.Getenv("PODSTALK_ALLOW_SIGNUP"); v != "" {
+		allowSignup = envBool(v)
+	}
+```
+
+Change the `authH` literal to include the flag:
+
+```go
+	authH := &handler.AuthHandler{Store: st, Sessions: sessions, Tpl: tpl, AllowSignup: allowSignup}
+```
+
+At the bottom (near `envOrDefault`), add the `envBool` helper:
+
+```go
+// envBool interprets a string as a truthy boolean.
+func envBool(v string) bool {
+	if b, err := strconv.ParseBool(v); err == nil {
+		return b
+	}
+	switch strings.ToLower(strings.TrimSpace(v)) {
+	case "yes", "on":
+		return true
+	}
+	return false
+}
+```
+
+Add `"strings"` to the imports if not already present (it is not present in `main.go`; add it).
+
+- [ ] **Step 3: Commit**
+
+```bash
+git add main.go
+git commit -m "Read PODSTALK_ALLOW_SIGNUP env var to control sign-up"
+```
+
+---
+
+### Task 3: Verify
+
+- [ ] **Step 1: Run the build script per AGENTS.md**
+
+Run: `./scripts/build`
+Expected: PASS (gofmt, go vet, go build, docker build all succeed).
+
+- [ ] **Step 2: Manual sanity check (sandbox permitting)**
+
+Run: `PODSTALK_ALLOW_SIGNUP=true go run . &` then `curl -s -o /dev/null -w "%{http_code}\n" -X GET localhost:8080/signup` → expect a 200 render.
+Run: `PODSTALK_ALLOW_SIGNUP=false go run . &` then `curl -s -o /dev/null -w "%{http_code}\n" -X GET localhost:8080/signup` → expect 303 redirect to `/signin`.
+
+- [ ] **Step 3: Final commit (if the build produced no fixes) and push**
+
+```bash
+git status
+git push
+```
+
+---
+
+## Self-Review
+
+**1. Spec coverage:**
+- Env var `PODSTALK_ALLOW_SIGNUP` parsed in `main.go` → Task 2 Step 2. ✓
+- Default (unset) = disabled → Task 2 Step 2 (`allowSignup := false`, only overridden when set non-empty). ✓
+- Truthy values (`true`, `1`, `yes`, `on`) enabled → `ParseBool` covers `1`/`true`, the switch covers `yes`/`on`. ✓
+- Signup handler redirects when disabled → Task 1 Step 1. ✓
+- Sign-in "Sign Up" link driven by same flag → Task 1 Steps 2–3 (`HasUser`). ✓
+- `store.UserCount()` unchanged → noted in File Structure. ✓
+
+**2. Placeholder scan:** No TBD/TODO; every task has concrete code. ✓
+
+**3. Type consistency:** `AllowSignup` field, `allowSignup()` method, and `envBool` helper are named consistently throughout. ✓

docs/specs/2026-08-19-allow-signup-env-design.md

@@ -0,0 +1,63 @@
+# Allow Sign-Up Via Environment Variable
+
+Date: 2026-08-19
+Status: Draft
+
+## Summary
+
+Replace the current "count of users" check that gates sign-up with a
+single environment variable. This lets an operator explicitly control
+whether public sign-up is available, instead of Podstalk inferring it
+from how many users already exist.
+
+## Motivation
+
+Today `ServeSignup` disables sign-up once a user already exists
+(`store.UserCount() > 0`). That is implicit and easy to get wrong: the
+first user must register before anyone can log in, and once that happens
+no one can ever register again. Controlling this with an explicit
+environment variable is predictable and self-documenting.
+
+## Behavior
+
+New environment variable: `PODSTALK_ALLOW_SIGNUP`.
+
+- Unset or any falsy value (`false`, `0`, `no`, `off`): sign-up **disabled**.
+- Truthy value (`true`, `1`, `yes`, `on`): sign-up **enabled**.
+
+Default (unset) is **disabled**.
+
+## Changes
+
+### `main.go`
+
+Read `PODSTALK_ALLOW_SIGNUP` from the environment and resolve it with a
+truthy-value parser. Set the resulting boolean on the `AuthHandler`.
+
+### `handler/auth.go`
+
+- Add an `AllowSignup bool` field to `AuthHandler`.
+- `ServeSignup`: redirect to `/signin` when `!AllowSignup` (replaces the
+  `UserCount() > 0` check).
+- Replace the `hasUsers()` helper (driven by user count) with a check on
+  `AllowSignup`, so the Sign In page shows/ hides the "Sign Up" nav link
+  based on whether sign-up is enabled. The sign-in template passes
+  `AllowSignup` and renders the link with `{{if .AllowSignup}}`.
+
+### Unchanged
+
+`store.UserCount()` remains in the store package. It is no longer used by
+authentication but is left in place as a general utility.
+
+## Out of Scope
+
+- No admin/user-management UI to invite specific users.
+- No change to the existing `adduser` CLI command (operator provisioning
+  still works regardless of the sign-up toggle).
+- No change to sign-in/sign-out behavior.
+
+## Testing
+
+- `scripts/build` passes (gofmt, go vet, go build, docker build).
+- Manual verification is limited by the sandbox; behavior relies on the
+  straightforward boolean branch and the truthy parser.

handler/auth.go

@@ -51,11 +51,11 @@ type AuthHandler struct {
 	Store       *store.Store
 	Sessions    *SessionStore
 	Tpl         *Templates
+	AllowSignup bool
 }
 
 func (h *AuthHandler) ServeSignup(w http.ResponseWriter, r *http.Request) {
-	count, err := h.Store.UserCount()
-	if err == nil && count > 0 {
+	if !h.AllowSignup {
 		http.Redirect(w, r, "/signin", http.StatusSeeOther)
 		return
 	}
@@ -97,14 +97,13 @@ func (h *AuthHandler) ServeSignup(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func (h *AuthHandler) hasUsers() bool {
-	count, err := h.Store.UserCount()
-	return err == nil && count > 0
+func (h *AuthHandler) allowSignup() bool {
+	return h.AllowSignup
 }
 
 func (h *AuthHandler) ServeSignin(w http.ResponseWriter, r *http.Request) {
 	if r.Method == http.MethodGet {
-		h.Tpl.Render(w, "signin", map[string]any{"HasUser": h.hasUsers()})
+		h.Tpl.Render(w, "signin", map[string]any{"AllowSignup": h.allowSignup()})
 		return
 	}
 
@@ -114,12 +113,12 @@ func (h *AuthHandler) ServeSignin(w http.ResponseWriter, r *http.Request) {
 
 		user, err := h.Store.UserByEmail(email)
 		if err != nil {
-			h.Tpl.Render(w, "signin", map[string]any{"Error": "Invalid email or password.", "HasUser": h.hasUsers()})
+			h.Tpl.Render(w, "signin", map[string]any{"Error": "Invalid email or password.", "AllowSignup": h.allowSignup()})
 			return
 		}
 
 		if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(password)); err != nil {
-			h.Tpl.Render(w, "signin", map[string]any{"Error": "Invalid email or password.", "HasUser": h.hasUsers()})
+			h.Tpl.Render(w, "signin", map[string]any{"Error": "Invalid email or password.", "AllowSignup": h.allowSignup()})
 			return
 		}
 

main.go

@@ -8,6 +8,8 @@ import (
 	"net/http"
 	"os"
 	"runtime/debug"
+	"strconv"
+	"strings"
 
 	"golang.org/x/crypto/bcrypt"
 
@@ -42,6 +44,11 @@ func main() {
 		baseURL = "http://localhost:8080"
 	}
 
+	allowSignup := false
+	if v := os.Getenv("PODSTALK_ALLOW_SIGNUP"); v != "" {
+		allowSignup = envBool(v)
+	}
+
 	st, err := store.New(dbPath)
 	if err != nil {
 		log.Fatalf("failed to open database: %v", err)
@@ -58,7 +65,7 @@ func main() {
 
 	authMid := &handler.AuthMiddleware{Store: st, Sessions: sessions}
 
-	authH := &handler.AuthHandler{Store: st, Sessions: sessions, Tpl: tpl}
+	authH := &handler.AuthHandler{Store: st, Sessions: sessions, Tpl: tpl, AllowSignup: allowSignup}
 	epH := &handler.EpisodeHandler{
 		Store:     st,
 		Tpl:       tpl,
@@ -157,3 +164,15 @@ func envOrDefault(key, def string) string {
 	}
 	return def
 }
+
+// envBool interprets a string as a truthy boolean.
+func envBool(v string) bool {
+	if b, err := strconv.ParseBool(v); err == nil {
+		return b
+	}
+	switch strings.ToLower(strings.TrimSpace(v)) {
+	case "yes", "on":
+		return true
+	}
+	return false
+}

template/signin.html

@@ -11,7 +11,7 @@
     <nav class="nb-navbar" role="navigation" aria-label="Main navigation">
         <a href="/" class="nb-navbar-brand" aria-label="Go to homepage">Podstalk</a>
         <ul class="nb-navbar-nav" role="menubar">
-            {{if not .HasUser}}
+            {{if .AllowSignup}}
             <li class="nb-navbar-item" role="none">
                 <a href="/signup" class="nb-navbar-link" role="menuitem">Sign Up</a>
             </li>