feat: add expense editing - view and edit all existing receipts

- Added ✏️ edit button on every expense in the list
- Clicking loads the receipt form pre-filled with the expense data
- Changes are saved via PUT /expenses/{id}
- Receipt form auto-switches between create (POST) and edit (PUT) mode
- Full HTMX multi-target response: form resets + list refreshes

internal/database/db.go

@@ -336,3 +336,39 @@ func GetExpensesByEvent(db *sql.DB, eventID string) ([]Expense, error) {
 	}
 	return expenses, rows.Err()
 }
+
+// GetExpenseByID returns a single expense by its ID, or nil if not found.
+func GetExpenseByID(db *sql.DB, id string) (*Expense, error) {
+	row := db.QueryRow(
+		`SELECT id, event_id, amount, currency, converted_amount, base_currency,
+		        merchant, category, COALESCE(description, ''), date, image_path, created_at
+		 FROM expenses WHERE id = ?`, id)
+	e := &Expense{}
+	if err := row.Scan(
+		&e.ID, &e.EventID, &e.Amount, &e.Currency, &e.ConvertedAmount, &e.BaseCurrency,
+		&e.Merchant, &e.Category, &e.Description, &e.Date, &e.ImagePath, &e.CreatedAt,
+	); err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil
+		}
+		log.Printf("ERROR [%s] database: GetExpenseByID(%s): %v",
+			time.Now().Format(time.RFC3339), id, err)
+		return nil, err
+	}
+	return e, nil
+}
+
+// UpdateExpense updates all editable fields of an existing expense.
+func UpdateExpense(db *sql.DB, expense Expense) error {
+	_, err := db.Exec(
+		`UPDATE expenses SET amount=?, currency=?, converted_amount=?, base_currency=?,
+		 merchant=?, category=?, description=?, date=? WHERE id=?`,
+		expense.Amount, expense.Currency, expense.ConvertedAmount, expense.BaseCurrency,
+		expense.Merchant, expense.Category, expense.Description, expense.Date, expense.ID,
+	)
+	if err != nil {
+		log.Printf("ERROR [%s] database: UpdateExpense(%s): %v",
+			time.Now().Format(time.RFC3339), expense.ID, err)
+	}
+	return err
+}

internal/handlers/expenses.go

@@ -20,6 +20,7 @@ import (
 	"github.com/expenseflow/internal/ai"
 	"github.com/expenseflow/internal/database"
 	"github.com/expenseflow/internal/utils"
+	"github.com/go-chi/chi/v5"
 )
 
 // ---------------------------------------------------------------------------
@@ -333,6 +334,148 @@ func (h *ExpenseHandler) SaveExpense(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprintf(w, `<div id="expense-list" hx-swap-oob="true">%s</div>`, listBuf.String())
 }
 
+// ---------------------------------------------------------------------------
+// GET /expenses/{id}/edit — EditExpense
+// ---------------------------------------------------------------------------
+
+// EditExpense returns the receipt form pre-filled with an existing expense's
+// data, allowing the user to edit and re-save it.
+func (h *ExpenseHandler) EditExpense(w http.ResponseWriter, r *http.Request) {
+	expenseID := chi.URLParam(r, "id")
+	if expenseID == "" {
+		http.Error(w, "Missing expense ID", http.StatusBadRequest)
+		return
+	}
+
+	expense, err := database.GetExpenseByID(h.DB, expenseID)
+	if err != nil {
+		log.Printf("ERROR [%s] handlers: EditExpense: GetExpenseByID(%s): %v",
+			time.Now().Format(time.RFC3339), expenseID, err)
+		http.Error(w, "Failed to retrieve expense", http.StatusInternalServerError)
+		return
+	}
+	if expense == nil {
+		http.Error(w, "Expense not found", http.StatusNotFound)
+		return
+	}
+
+	tmpl, err := template.ParseFiles("templates/receipt_form.html")
+	if err != nil {
+		log.Printf("ERROR [%s] handlers: EditExpense: parse template: %v",
+			time.Now().Format(time.RFC3339), err)
+		http.Error(w, "Template error", http.StatusInternalServerError)
+		return
+	}
+
+	data := map[string]interface{}{
+		"ImagePath":       expense.ImagePath,
+		"AIError":         "",
+		"Amount":          strconv.FormatFloat(expense.Amount, 'f', 2, 64),
+		"Currency":        expense.Currency,
+		"Merchant":        expense.Merchant,
+		"Category":        expense.Category,
+		"Date":            expense.Date,
+		"Description":     expense.Description,
+		"BaseCurrency":    expense.BaseCurrency,
+		"ExchangeRate":    0.0,
+		"ConvertedAmount": strconv.FormatFloat(expense.ConvertedAmount, 'f', 2, 64),
+		"EditID":          expense.ID,
+	}
+
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	if err := tmpl.Execute(w, data); err != nil {
+		log.Printf("ERROR [%s] handlers: EditExpense: execute template: %v",
+			time.Now().Format(time.RFC3339), err)
+	}
+}
+
+// ---------------------------------------------------------------------------
+// PUT /expenses/{id} — UpdateExpense
+// ---------------------------------------------------------------------------
+
+// UpdateExpense updates an existing expense record with form data and returns
+// the updated expense list via HTMX multi-target response.
+func (h *ExpenseHandler) UpdateExpense(w http.ResponseWriter, r *http.Request) {
+	expenseID := chi.URLParam(r, "id")
+	if expenseID == "" {
+		http.Error(w, "Missing expense ID", http.StatusBadRequest)
+		return
+	}
+
+	if err := r.ParseForm(); err != nil {
+		log.Printf("ERROR [%s] handlers: UpdateExpense: parse form: %v",
+			time.Now().Format(time.RFC3339), err)
+		http.Error(w, "Cannot parse form data", http.StatusBadRequest)
+		return
+	}
+
+	amount, _ := strconv.ParseFloat(r.FormValue("amount"), 64)
+	convertedAmount, _ := strconv.ParseFloat(r.FormValue("converted_amount"), 64)
+	baseCurrency := r.FormValue("base_currency")
+	if baseCurrency == "" {
+		baseCurrency = r.FormValue("currency")
+		convertedAmount = amount
+	}
+
+	// Fetch the existing expense to preserve the event_id and image_path.
+	existing, err := database.GetExpenseByID(h.DB, expenseID)
+	if err != nil || existing == nil {
+		log.Printf("ERROR [%s] handlers: UpdateExpense: get existing: %v",
+			time.Now().Format(time.RFC3339), err)
+		http.Error(w, "Expense not found", http.StatusNotFound)
+		return
+	}
+
+	expense := database.Expense{
+		ID:              expenseID,
+		EventID:         existing.EventID,
+		Amount:          amount,
+		Currency:        r.FormValue("currency"),
+		ConvertedAmount: convertedAmount,
+		BaseCurrency:    baseCurrency,
+		Merchant:        r.FormValue("merchant"),
+		Category:        r.FormValue("category"),
+		Description:     r.FormValue("description"),
+		Date:            r.FormValue("date"),
+		ImagePath:       existing.ImagePath,
+	}
+
+	if err := database.UpdateExpense(h.DB, expense); err != nil {
+		log.Printf("ERROR [%s] handlers: UpdateExpense: %v", time.Now().Format(time.RFC3339), err)
+		http.Error(w, "Failed to update expense", http.StatusInternalServerError)
+		return
+	}
+
+	// Return updated expense list via HTMX.
+	expenses, err := database.GetExpensesByEvent(h.DB, existing.EventID)
+	if err != nil {
+		log.Printf("ERROR [%s] handlers: UpdateExpense: fetch expenses: %v",
+			time.Now().Format(time.RFC3339), err)
+		http.Error(w, "Failed to fetch expenses", http.StatusInternalServerError)
+		return
+	}
+
+	listTmpl, err := template.ParseFiles("templates/expense_list.html")
+	if err != nil {
+		log.Printf("ERROR [%s] handlers: UpdateExpense: parse template: %v",
+			time.Now().Format(time.RFC3339), err)
+		http.Error(w, "Template error", http.StatusInternalServerError)
+		return
+	}
+
+	var listBuf strings.Builder
+	if err := listTmpl.Execute(&listBuf, map[string]interface{}{"Expenses": expenses}); err != nil {
+		log.Printf("ERROR [%s] handlers: UpdateExpense: execute template: %v",
+			time.Now().Format(time.RFC3339), err)
+		http.Error(w, "Template error", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	fmt.Fprintf(w, `<div id="receipt-form" hx-swap-oob="true"><div class="bg-green-100 border border-green-400 text-green-700 px-4 py-3 rounded mb-4">Expense updated successfully!</div></div>`)
+	fmt.Fprintf(w, `<div id="expense-list" hx-swap-oob="true">%s</div>`, listBuf.String())
+}
+
 // ---------------------------------------------------------------------------
 // Cookie helpers (shared with events.go via package-level access)
 // ---------------------------------------------------------------------------

main.go

@@ -174,6 +174,8 @@ func main() {
 		// Expenses.
 		r.Post("/expenses/upload", expenseHandler.UploadReceipt)
 		r.Post("/expenses", expenseHandler.SaveExpense)
+		r.Get("/expenses/{id}/edit", expenseHandler.EditExpense)
+		r.Put("/expenses/{id}", expenseHandler.UpdateExpense)
 
 		// Filing.
 		r.Post("/events/{id}/file", fileHandler.FileEvent)

templates/dashboard.html

@@ -113,6 +113,11 @@
                                hx-get="/events/{{.ID}}/expenses" hx-target="body" hx-push-url="true">
                                 Add Expenses
                             </a>
+                            <a href="/events/{{.ID}}/expenses" class="btn btn-secondary btn-sm"
+                               hx-get="/events/{{.ID}}/expenses" hx-target="body" hx-push-url="true"
+                               style="border-color: #10b981; color: #10b981;">
+                                File Report
+                            </a>
                             {{else}}
                             <button class="btn btn-secondary btn-sm"
                                     hx-put="/events/{{.ID}}/reopen"

templates/event_expenses.html

@@ -83,6 +83,15 @@
                             </div>
                             {{end}}
                         </div>
+                        <div style="display: flex; align-items: center; margin-left: 0.5rem;">
+                            <button class="btn btn-sm" style="background: none; border: 1px solid #d1d5db; border-radius: 0.375rem; padding: 0.25rem 0.5rem; font-size: 0.75rem; cursor: pointer;"
+                                    hx-get="/expenses/{{.ID}}/edit"
+                                    hx-target="#receipt-form"
+                                    hx-swap="innerHTML"
+                                    title="Edit expense">
+                                ✏️
+                            </button>
+                        </div>
                     </div>
                     {{end}}
                 </div>

templates/expense_list.html

@@ -28,6 +28,15 @@
                 </div>
                 {{end}}
             </div>
+            <div style="display: flex; align-items: center; margin-left: 0.5rem;">
+                <button class="btn btn-sm" style="background: none; border: 1px solid #d1d5db; border-radius: 0.375rem; padding: 0.25rem 0.5rem; font-size: 0.75rem; cursor: pointer;"
+                        hx-get="/expenses/{{.ID}}/edit"
+                        hx-target="#receipt-form"
+                        hx-swap="innerHTML"
+                        title="Edit expense">
+                    ✏️
+                </button>
+            </div>
         </div>
         {{end}}
     </div>

templates/receipt_form.html

@@ -15,9 +15,15 @@
             <span class="badge badge-open" style="margin-left: auto;">AI Extracted</span>
         </div>
 
+        {{if .EditID}}
+        <form hx-put="/expenses/{{.EditID}}" hx-target="#receipt-form" hx-swap="outerHTML"
+              hx-indicator="#save-indicator">
+        {{else}}
         <form hx-post="/expenses" hx-target="#receipt-form" hx-swap="outerHTML"
               hx-indicator="#save-indicator">
+        {{end}}
             <input type="hidden" name="image_path" value="{{.ImagePath}}">
+            {{if .EditID}}<input type="hidden" name="edit_id" value="{{.EditID}}">{{end}}
 
             <div class="form-row">
                 <div class="form-group">
@@ -109,7 +115,7 @@
             <div style="display: flex; gap: 0.5rem;">
                 <button type="submit" class="btn btn-primary" id="save-indicator">
                     <span class="spinner htmx-indicator"></span>
-                    Save Expense
+                    {{if .EditID}}Update Expense{{else}}Save Expense{{end}}
                 </button>
                 <button type="button" class="btn btn-secondary"
                         onclick="document.getElementById('receipt-form').innerHTML = ''">