phase 0-2 complete

internal/server/tilecache.go

@@ -0,0 +1,34 @@
+package server
+
+import "sync"
+
+// TileCache is a thread-safe in-memory cache for rendered PNG tiles.
+// Keys are "z/x/y". The entire cache is invalidated on each new radar scan.
+type TileCache struct {
+	mu    sync.RWMutex
+	tiles map[string][]byte
+}
+
+func NewTileCache() *TileCache {
+	return &TileCache{tiles: make(map[string][]byte)}
+}
+
+func (c *TileCache) Get(key string) ([]byte, bool) {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	v, ok := c.tiles[key]
+	return v, ok
+}
+
+func (c *TileCache) Set(key string, data []byte) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.tiles[key] = data
+}
+
+// Invalidate clears all cached tiles. Call this after each new radar product is loaded.
+func (c *TileCache) Invalidate() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.tiles = make(map[string][]byte)
+}