Parallelize Trello card fetching for improved performance

Replaced sequential card fetching in GetBoardsWithCards with concurrent
goroutines limited by a semaphore (max 5 concurrent requests). This
significantly reduces load times for users with multiple boards.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

1 files changed, 20 insertions, 7 deletions

diff --git a/internal/api/trello.go b/internal/api/trello.go
index 899f6df..cecf0dc 100644
--- a/internal/api/trello.go
+++ b/internal/api/trello.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"sync"
 	"time"
 
 	"task-dashboard/internal/models"
@@ -193,16 +194,28 @@ func (c *TrelloClient) GetBoardsWithCards(ctx context.Context) ([]models.Board,
 		return nil, err
 	}
 
-	// Fetch cards for each board
+	var wg sync.WaitGroup
+	sem := make(chan struct{}, 5) // Limit to 5 concurrent requests
+
 	for i := range boards {
-		cards, err := c.GetCards(ctx, boards[i].ID)
-		if err != nil {
-			// Log error but continue with other boards
-			continue
-		}
-		boards[i].Cards = cards
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+
+			// Acquire semaphore
+			sem <- struct{}{}
+			defer func() { <-sem }()
+
+			cards, err := c.GetCards(ctx, boards[i].ID)
+			if err == nil {
+				// It is safe to write to specific indices of the slice concurrently
+				boards[i].Cards = cards
+			}
+		}(i)
 	}
 
+	wg.Wait()
+
 	return boards, nil
 }