# M6.3 — Go-native `/juniors` page

## Context

The Go rewrite is in milestone M6 (Go-native HTML frontend). M6.2 shipped the `/adults` page in commit `c85748b`; the [progress tracker](../../srv/personal/fuj-management/docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md) line 115 names M6.3 as:

> `/juniors` page: same structure + per-month J/A attendance breakdown + `"?"` sentinel rendering

The Go side already has `buildJuniorsResponse` (M5.2) that produces the full JSON view model, and the JuniorsResponse uses the same `MemberRow`/`MonthCell`/`TotalCell` types as `AdultsResponse`. Critically, `buildJuniorMemberRow` ([go/internal/web/api/build_juniors.go:142](../../srv/personal/fuj-management/go/internal/web/api/build_juniors.go#L142)) already bakes the J/A breakdown (e.g. `"3/500 CZK (4:2J,2A)"`) and the `"?"` sentinel into `MonthCell.Text` — no template-level junior-specific logic is required for the M6.3 table.

Today `juniors.tmpl` is a 4-line "Coming in M6.3" placeholder and `HTMLHandler.ServeJuniors` ([html_handler.go:35](../../srv/personal/fuj-management/go/internal/web/html_handler.go#L35)) just renders that placeholder. Goal of M6.3: produce a working `/juniors` page that mirrors the structure of `/adults` and reaches feature parity with the Python `/juniors` route.

## Approach

Mirror the M6.2 pattern exactly:

1. **Extract `AssembleJuniors(ctx)`** from the JSON handler so HTML + JSON share one view-model assembly path (the parity contract).
2. **Add `JuniorsPageData`** wrapper type next to `AdultsPageData` in `render.go`.
3. **Replace `juniors.tmpl`** with an adults-shaped layout. Because `JuniorsResponse` shares the same field names used by `adults.tmpl` (`Months`, `RawMonths`, `Results`, `Totals`, `Credits`, `Debts`, `AttendanceURL`, `PaymentsURL`, `BankAccount`, `CurrentMonth`), the template body is essentially copy/paste with one parity tweak (see "Decisions" below).
4. **Wire `HTMLHandler.ServeJuniors`** to call `AssembleJuniors` and render the new template, parallel to `ServeAdults`.

No new CSS, no new JS — `filters.js` and the `cell-*` classes (lifted in M6.1) already cover juniors.

## Files to modify

| File | Change |
| --- | --- |
| [go/internal/web/api/handler.go](../../srv/personal/fuj-management/go/internal/web/api/handler.go) | Add `AssembleJuniors(ctx) (JuniorsResponse, error)`; refactor existing `ServeJuniors` to call it (mirrors `AssembleAdults` at line 47). |
| [go/internal/web/render.go](../../srv/personal/fuj-management/go/internal/web/render.go) | Add `JuniorsPageData` struct (PageData + `Data api.JuniorsResponse` + `Error string`). |
| [go/internal/web/html_handler.go](../../srv/personal/fuj-management/go/internal/web/html_handler.go) | Replace stub `ServeJuniors` with the same shape as `ServeAdults` (lines 20–33). |
| [go/internal/web/templates/juniors.tmpl](../../srv/personal/fuj-management/go/internal/web/templates/juniors.tmpl) | Replace placeholder with a structurally identical copy of [adults.tmpl](../../srv/personal/fuj-management/go/internal/web/templates/adults.tmpl), with the title swapped to "Juniors Dashboard" and the Unmatched section removed (parity with Python). |
| [docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md](../../srv/personal/fuj-management/docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md) | Tick `M6.3` once merged, append merge SHA. |
| [CHANGELOG.md](../../srv/personal/fuj-management/CHANGELOG.md) | New top-most entry per CLAUDE.md format. |

## Decisions captured

- **No "Unmatched Transactions" section on `/juniors`.** Python's [templates/juniors.html](../../srv/personal/fuj-management/templates/juniors.html) renders only Credits + Debts (no Unmatched block). Although `JuniorsResponse.Unmatched` is populated, parity says we don't render it on juniors. The data stays available for the modal in M6.5.
- **Reuse `qrHref` / `qrHrefAll` template funcs** from [render.go:35–57](../../srv/personal/fuj-management/go/internal/web/render.go#L35-L57). They are name-only (not adult-specific) and already on `tmplFuncs`.
- **Reuse the existing `cell-empty / cell-unpaid / cell-unpaid-current / cell-ok / cell-overridden` cell-class branching** from `adults.tmpl` lines 60–67 verbatim. The "?" sentinel is rendered as plain `{{$cell.Text}}` text — no template branch needed because `buildJuniorMemberRow` produces `"?"` or `"? CZK"` already.
- **No template helper extraction** (e.g. shared `_table_section.tmpl`). The two templates will be near-duplicates, but extracting a shared partial now is premature — wait until M6.4 or later when patterns settle. M6.2 didn't extract one either.
- **Branch**: `feat/go-m6-3-juniors-page`, MR via `tea pr create` per CLAUDE.md.

## Verification

End-to-end smoke (parallel-running both backends as in M5/M6.2):

1. `cd go && make run` (or whatever target boots the Go server on :8080).
2. Browser-load `http://localhost:8080/juniors`. Confirm:
   - Member rows render with cells containing fee + attendance breakdown like `0/500 CZK (3:2J,1A)`.
   - At least one `"?"` cell visible (any junior with exactly one session in some month).
   - Filter input narrows rows by name; From/To month selects hide columns via `data-month-idx`.
   - `Pay` button visible on past-month unpaid cells; clicking links to `/qr?...`. (The QR endpoint itself lands in M6.6 — only the link target is in scope here.)
   - `Pay All` visible on rows with `Balance < 0`.
   - TOTAL row sums correctly per month.
   - Credits + Debts sections render when present; no Unmatched section.
3. JSON parity: `make parity` against the M3 fixture corpus must still report zero non-allowlisted diffs for `/api/juniors` (the `AssembleJuniors` extraction must not change wire output).
4. Compare side-by-side against Python `/juniors` on :5001 for the same fixture; the table cells should match cell-for-cell modulo the known M5 allowlist.

## Out of scope

- Modal (`[i]` info button + `#memberModal`) — that is M6.5.
- QR endpoint, `/sync-bank`, `/flush-cache`, `/version` pages — M6.6.
- Embed.FS deploy verification — M6.7.

## Plan-file relocation

Per [CLAUDE.md](../../srv/personal/fuj-management/CLAUDE.md) "Plans" section, plan files belong in `docs/plans/YYYY-MM-DD-HHMM-<slug>.md` inside the repo. Plan mode forced this draft into `~/.claude/plans/`; first step after ExitPlanMode is to copy this file to `docs/plans/2026-05-08-HHMM-go-m6-3-juniors-page.md` (resolving the timestamp at that moment) and commit it on the feature branch alongside the implementation.