refactor: split jikan client into smaller domain files

internal/jikan/relations.go

@@ -0,0 +1,93 @@
+package jikan
+
+import "fmt"
+
+// GetRelationsData fetches the raw relationships for an anime
+func (c *Client) GetRelationsData(id int) (JikanRelationsResponse, error) {
+	if cached, ok := c.relationsCache.Get(id); ok {
+		return cached, nil
+	}
+
+	var result JikanRelationsResponse
+	reqURL := fmt.Sprintf("%s/anime/%d/relations", c.baseURL, id)
+	if err := c.fetchWithRetry(reqURL, &result); err != nil {
+		return JikanRelationsResponse{}, err
+	}
+
+	c.relationsCache.Add(id, result)
+	return result, nil
+}
+
+// findFirstAnimeRelation extracts the first related anime ID for a specific relation type
+func findFirstAnimeRelation(res JikanRelationsResponse, relType string) *int {
+	for _, group := range res.Data {
+		if group.Relation == relType {
+			for _, entry := range group.Entry {
+				if entry.Type == "anime" {
+					id := entry.MalID
+					return &id
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// fetchChain recursively builds the relational chain (Prequels or Sequels)
+func (c *Client) fetchChain(startID int, direction string, visited map[int]bool) []RelationEntry {
+	rels, err := c.GetRelationsData(startID)
+	if err != nil {
+		return nil
+	}
+
+	nextIDPtr := findFirstAnimeRelation(rels, direction)
+	if nextIDPtr == nil {
+		return nil
+	}
+
+	nextID := *nextIDPtr
+	if visited[nextID] { // prevent loops
+		return nil
+	}
+	visited[nextID] = true
+
+	anime, err := c.GetAnimeByID(nextID)
+	if err != nil {
+		return nil
+	}
+
+	entry := RelationEntry{Anime: anime, IsCurrent: false}
+	rest := c.fetchChain(nextID, direction, visited)
+
+	if direction == "Prequel" {
+		return append(rest, entry)
+	}
+	return append([]RelationEntry{entry}, rest...)
+}
+
+// GetFullRelations resolves the full Prequel/Sequel chronological chain synchronously
+func (c *Client) GetFullRelations(id int) []RelationEntry {
+	currentAnime, err := c.GetAnimeByID(id)
+	if err != nil {
+		return nil
+	}
+
+	visited := map[int]bool{id: true}
+
+	prequels := c.fetchChain(id, "Prequel", visited)
+
+	// Clone visited set for sequels so we don't block valid paths if there's weird branching
+	visitedSeq := make(map[int]bool)
+	for k, v := range visited {
+		visitedSeq[k] = v
+	}
+
+	sequels := c.fetchChain(id, "Sequel", visitedSeq)
+
+	var result []RelationEntry
+	result = append(result, prequels...)
+	result = append(result, RelationEntry{Anime: currentAnime, IsCurrent: true})
+	result = append(result, sequels...)
+
+	return result
+}