fix(steam): stop attributing advertised mods' IDs to an item

pkg/steam/item.go

@@ -50,23 +50,84 @@ type ParsedItem struct {
 }
 
 // Parse scrapes the item description for the mod IDs and map folders the game
-// uses. It tolerates the two casing variants Steam mod authors use in practice.
+// uses. Some descriptions advertise *other* mods by reproducing their PZ footer
+// (a "Workshop ID:" line paired with a "Mod ID:" / "Map Folder:" line), which
+// would otherwise leak those foreign IDs into this item. To guard against that,
+// each Mod ID / Map Folder is attributed to the nearest "Workshop ID:" line in
+// either direction (authors write the pair in both orders, sometimes separated
+// by a blank line; ties favour the item's own ID) and is dropped only when that
+// nearest Workshop ID belongs to a *different* item. Attribution only kicks in
+// once the item's own Workshop ID is seen; descriptions that never state it, or
+// omit Workshop IDs entirely, keep every entry as before. It tolerates the
+// casing variants ("Mod ID:"/"ModID:", "Workshop ID:"/"WorkshopID:") authors
+// use in practice.
 func (w *WorkshopItem) Parse() *ParsedItem {
+	lines := strings.Split(w.Description, "\n")
+
+	// First pass: locate every Workshop ID line and note whether our own appears.
+	type widLine struct {
+		idx int
+		own bool
+	}
+	var wids []widLine
+	ownSeen := false
+	for i, line := range lines {
+		if v, ok := fieldValue(strings.TrimSpace(line), "Workshop ID:", "WorkshopID:"); ok {
+			own := v != "" && v == w.PublishedFileID
+			wids = append(wids, widLine{idx: i, own: own})
+			ownSeen = ownSeen || own
+		}
+	}
+
+	// keep reports whether the footer entry on line idx should be attributed to
+	// this item. With no own Workshop ID to anchor against, keep everything.
+	keep := func(idx int) bool {
+		if !ownSeen {
+			return true
+		}
+		bestDist, nearestOwn := -1, true
+		for _, wl := range wids {
+			d := wl.idx - idx
+			if d < 0 {
+				d = -d
+			}
+			if bestDist == -1 || d < bestDist || (d == bestDist && wl.own) {
+				bestDist, nearestOwn = d, wl.own
+			}
+		}
+		return nearestOwn
+	}
+
 	var mods, maps []string
-	for _, line := range strings.Split(w.Description, "\n") {
+	for i, line := range lines {
 		line = strings.TrimSpace(line)
-		switch {
-		case strings.HasPrefix(line, "Mod ID: "):
-			mods = append(mods, strings.TrimSpace(strings.TrimPrefix(line, "Mod ID: ")))
-		case strings.HasPrefix(line, "ModID: "):
-			mods = append(mods, strings.TrimSpace(strings.TrimPrefix(line, "ModID: ")))
-		case strings.HasPrefix(line, "Map Folder: "):
-			maps = append(maps, strings.TrimSpace(strings.TrimPrefix(line, "Map Folder: ")))
+		if v, ok := fieldValue(line, "Mod ID:", "ModID:"); ok {
+			if keep(i) {
+				mods = append(mods, v)
+			}
+		} else if v, ok := fieldValue(line, "Map Folder:"); ok {
+			if keep(i) {
+				maps = append(maps, v)
+			}
 		}
 	}
 	return &ParsedItem{Mods: domain.Dedupe(mods), Maps: domain.Dedupe(maps)}
 }
 
+// fieldValue returns the trimmed value of the first "Key value" line among keys,
+// matching each key with a trailing space per the PZ footer convention (so
+// "Mod ID:Foo" without the space is not treated as a footer line), and whether
+// any key matched.
+func fieldValue(line string, keys ...string) (string, bool) {
+	for _, k := range keys {
+		p := k + " "
+		if strings.HasPrefix(line, p) {
+			return strings.TrimSpace(strings.TrimPrefix(line, p)), true
+		}
+	}
+	return "", false
+}
+
 // IsCollection reports whether the item is a Workshop collection.
 func (w *WorkshopItem) IsCollection() bool { return w.FileType == FileTypeCollection }
 

pkg/steam/item_test.go

@@ -0,0 +1,118 @@
+package steam
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestParseScopesToOwnWorkshopID(t *testing.T) {
+	tests := []struct {
+		name     string
+		id       string
+		desc     string
+		wantMods []string
+		wantMaps []string
+	}{
+		{
+			name: "advertised footer is ignored (real 3042138819 case)",
+			id:   "3042138819",
+			desc: "The new multiplayer true music jukebox is now available!\n" +
+				"True Music Jukebox\n" +
+				"https://steamcommunity.com/sharedfiles/filedetails/?id=3118990099\n" +
+				"Workshop ID: 3118990099\n" +
+				"Mod ID: TrueMusicJukebox\n" +
+				"\n" +
+				"Workshop ID: 3042138819\n" +
+				"Mod ID: FunctionalAppliances2\n",
+			wantMods: []string{"FunctionalAppliances2"},
+			wantMaps: []string{},
+		},
+		{
+			name: "several mod ids under the item's own workshop id are all kept",
+			id:   "555",
+			desc: "A bundle.\n" +
+				"Workshop ID: 555\n" +
+				"Mod ID: ModA\n" +
+				"Mod ID: ModB\n",
+			wantMods: []string{"ModA", "ModB"},
+			wantMaps: []string{},
+		},
+		{
+			name: "reversed footer (Mod ID before Workshop ID, blank between) is kept (real 3654929003 case)",
+			id:   "3654929003",
+			desc: "Other batch action work:\n" +
+				"https://steamcommunity.com/sharedfiles/filedetails/?id=3584890848 batch recipe action\n" +
+				"https://steamcommunity.com/sharedfiles/filedetails/?id=3660401764 pick everything on floor\n" +
+				"\n" +
+				"Mod ID: vac_mod_b42_4\n" +
+				"\n" +
+				"Workshop ID: 3654929003\n",
+			wantMods: []string{"vac_mod_b42_4"},
+			wantMaps: []string{},
+		},
+		{
+			name: "other mods advertised only as URLs do not cause drops",
+			id:   "100",
+			desc: "Check out my other mods:\n" +
+				"https://steamcommunity.com/sharedfiles/filedetails/?id=999\n" +
+				"Mod ID: MyMod\n" +
+				"Workshop ID: 100\n",
+			wantMods: []string{"MyMod"},
+			wantMaps: []string{},
+		},
+		{
+			name: "a separated foreign footer block is dropped, own block kept",
+			id:   "100",
+			desc: "Workshop ID: 999\n" +
+				"Mod ID: ForeignMod\n" +
+				"Map Folder: ForeignMap\n" +
+				"\n" +
+				"\n" +
+				"Workshop ID: 100\n" +
+				"Mod ID: MyMod\n" +
+				"Map Folder: MyMap\n",
+			wantMods: []string{"MyMod"},
+			wantMaps: []string{"MyMap"},
+		},
+		{
+			name: "no workshop id line falls back to keeping everything",
+			id:   "42",
+			desc: "A simple mod.\n" +
+				"Mod ID: Simple\n" +
+				"Map Folder: SimpleMap\n",
+			wantMods: []string{"Simple"},
+			wantMaps: []string{"SimpleMap"},
+		},
+		{
+			name: "casing variants are tolerated",
+			id:   "88",
+			desc: "WorkshopID: 88\n" +
+				"ModID: CasedMod\n",
+			wantMods: []string{"CasedMod"},
+			wantMaps: []string{},
+		},
+		{
+			name: "only a foreign workshop id present keeps everything (own id absent)",
+			id:   "200",
+			desc: "Check out my other mod:\n" +
+				"Workshop ID: 999\n" +
+				"Mod ID: OtherMod\n" +
+				"Mod ID: BareMod\n",
+			wantMods: []string{"OtherMod", "BareMod"},
+			wantMaps: []string{},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			w := WorkshopItem{PublishedFileID: tc.id, Description: tc.desc}
+			got := w.Parse()
+			if !reflect.DeepEqual(got.Mods, tc.wantMods) {
+				t.Errorf("mods = %#v, want %#v", got.Mods, tc.wantMods)
+			}
+			if !reflect.DeepEqual(got.Maps, tc.wantMaps) {
+				t.Errorf("maps = %#v, want %#v", got.Maps, tc.wantMaps)
+			}
+		})
+	}
+}