Separate current/former members with calculable period dates

- Add MemberGroup/BandGroup types and groupBandMembers/groupArtistMembers helpers
- Calculate membership duration in months from YYYY-MM since/until values
- Band view splits members into 在籍中 / 元メンバー sections with duration label
- Artist view splits bands into 在籍中 / 元在籍 sections with duration label
- Change since/until inputs to type="month" for structured data entry

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/app/lib/db.server.ts b/app/lib/db.server.ts
index cb51028..d3e5469 100644
--- a/app/lib/db.server.ts
+++ b/app/lib/db.server.ts
@@ -200,6 +200,86 @@ export interface ArtistRevision {
   created_at: string;
 }
 
+export interface MemberGroup {
+  artist_id: string;
+  artist_name: string;
+  artist_slug: string;
+  periods: BandMemberRow[];
+  is_current: boolean;
+  duration_months: number | null;
+}
+
+export interface BandGroup {
+  band_id: string;
+  band_name: string;
+  band_slug: string;
+  periods: ArtistMemberRow[];
+  is_current: boolean;
+  duration_months: number | null;
+}
+
+function parseYearMonth(s: string): { year: number; month: number } | null {
+  const m = s.match(/^(\d{4})-(\d{2})$/);
+  if (!m) return null;
+  return { year: parseInt(m[1]), month: parseInt(m[2]) };
+}
+
+function calcDurationMonths(since: string, until: string): number | null {
+  const from = parseYearMonth(since);
+  if (!from) return null;
+  const today = new Date();
+  const to = parseYearMonth(until) ?? { year: today.getFullYear(), month: today.getMonth() + 1 };
+  return Math.max(0, (to.year * 12 + to.month) - (from.year * 12 + from.month));
+}
+
+export function groupBandMembers(members: BandMemberRow[]): {
+  current: MemberGroup[];
+  former: MemberGroup[];
+  all: MemberGroup[];
+} {
+  const byArtist = new Map<string, BandMemberRow[]>();
+  for (const m of members) {
+    const list = byArtist.get(m.artist_id) ?? [];
+    list.push(m);
+    byArtist.set(m.artist_id, list);
+  }
+  const all: MemberGroup[] = [];
+  for (const [artistId, periods] of byArtist) {
+    const first = periods[0];
+    const is_current = periods.some((p) => !p.until);
+    const duration_months = periods.reduce<number | null>((acc, p) => {
+      const d = calcDurationMonths(p.since, p.until);
+      return d === null ? acc : (acc ?? 0) + d;
+    }, null);
+    all.push({ artist_id: artistId, artist_name: first.artist_name, artist_slug: first.artist_slug, periods, is_current, duration_months });
+  }
+  return { current: all.filter((g) => g.is_current), former: all.filter((g) => !g.is_current), all };
+}
+
+export function groupArtistMembers(members: ArtistMemberRow[]): {
+  current: BandGroup[];
+  former: BandGroup[];
+  all: BandGroup[];
+} {
+  const byBand = new Map<string, ArtistMemberRow[]>();
+  for (const m of members) {
+    const list = byBand.get(m.band_id) ?? [];
+    list.push(m);
+    byBand.set(m.band_id, list);
+  }
+  const all: BandGroup[] = [];
+  for (const [bandId, periods] of byBand) {
+    const first = periods[0];
+    const is_current = periods.some((p) => !p.until);
+    const duration_months = periods.reduce<number | null>((acc, p) => {
+      const d = calcDurationMonths(p.since, p.until);
+      return d === null ? acc : (acc ?? 0) + d;
+    }, null);
+    all.push({ band_id: bandId, band_name: first.band_name, band_slug: first.band_slug, periods, is_current, duration_months });
+  }
+  return { current: all.filter((g) => g.is_current), former: all.filter((g) => !g.is_current), all };
+}
+
 export function getIpAddress(request: Request): string {
   return (
     request.headers.get("x-forwarded-for")?.split(",")[0].trim() ??