pansy/DESIGN.md

Pansy — Design

Pansy is a self-hostable garden planning web app. A landscaping-style 2D editor: drag garden objects (raised beds, grow bags, containers, in-ground plots, trees, paths) onto a field at real-world scale; click into a plantable object to place freeform "plops" of plants — a few plops of garlic in one corner, herbs in another, beans along a side — and zoom out to still see what's planted where. React frontend, Go backend, clean JSON API, single static binary. Works on desktop and is mobile-usable (touch drag, pinch zoom).

Work is tracked in Gitea issues; the tracking epic links every piece in dependency order.

Decisions

• Placement model: freeform plops (not a square-foot grid), scaled by real plant spacing. Grid snapping may come later as a toggle.
• Stack: Go 1.26.x backend, module gitea.stevedudenhoeffer.com/steve/pansy; React + TypeScript + Vite + Tailwind frontend, production build embedded via embed.FS → one static binary (CGO_ENABLED=0).
• Users: multi-user with ownership. Users own gardens; a garden can be shared with other users as viewer (read) or editor (edit content). Owner additionally shares/deletes.
• Auth: OIDC-first (Authentik is the primary IdP), local argon2id passwords as an optional fallback.
• Agentic future: integration with majordomo/executus via typed Go tools (llm.DefineTool[Args]) wrapping the same service layer the REST API uses — not MCP/OpenAPI.

Domain model

SQLite, centimeters everywhere (display-side imperial conversion only), version INTEGER on every user-mutable row for conflict detection.

• users — email (unique), display_name, nullable argon2id password_hash, nullable oidc_issuer+oidc_subject (unique pair), is_admin. First registered user becomes admin. PANSY_REGISTRATION (open/closed) gates local signup. A user can be local-password, OIDC, or both (linked by email on first OIDC login).
• sessions — sha256-hashed random 32-byte token, user_id, 30-day sliding expiry. HttpOnly cookie holds the raw token. Sessions are pansy-local regardless of auth method.
• gardens — owner_id, name, width_cm, height_cm, unit_pref (metric|imperial), notes.
• garden_shares — (garden_id, user_id) unique, role viewer|editor, created_by. Owner is implicit via gardens.owner_id, never a share row.
• garden_objects — one polymorphic table: kind (bed|grow_bag|container|in_ground|tree|path|structure), name, shape (rect|circle; polygon + points JSON reserved in schema, not in the v1 editor), center x_cm,y_cm in garden space, width_cm,height_cm (circle: width=diameter), rotation_deg, z_index, plantable bool, nullable color override, props JSON for kind-specific extras (bed height, tree species…), notes.
• plants — catalog. owner_id NULL = built-in (~30 seeded via migration, read-only, clone to customize). name, category (vegetable|herb|flower|fruit|tree_shrub|cover), spacing_cm (mature spacing), color hex, icon (emoji string — zero assets in v1), nullable days_to_maturity, notes. Users see built-ins + their own.
• change_sets / revisions — the undo substrate. A change set groups the row-level revisions one logical operation produced (source ui/agent/api, summary, nullable agent_run_id, nullable reverts_id); a revision is (entity_type, entity_id, op, before, after) with full JSON row snapshots. The unit of undo is the operation, not the row. Revert is itself a change set, so an undo can be undone; it is version-guarded per entity and reports conflicts rather than clobbering a later edit. Garden deletion is deliberately not revertible (the cascade is invisible to the service, and would take the history with it).
• plantings ("plops") — object_id, plant_id, center x_cm,y_cm in the parent object's local frame (moving/rotating a bed moves its plants for free), radius_cm (a plop is a circular patch), nullable count (NULL = derived: max(1, round(π·r² / spacing_cm²))), nullable label, planted_at/removed_at dates. "Clear bed" sets removed_at; v1 shows rows where removed_at IS NULL. Year-over-year history and a future plan/scenario layer build on these dates without schema surgery.

Geometry

• Garden space: origin top-left, x→right, y→down (screen-aligned), cm.
• Objects: positioned by center point + rotation_deg clockwise about center → SVG translate(x y) rotate(deg) one-liners.
• Object local frame: origin at object center, axes aligned to the unrotated object. Plops live in this frame.
• Exactly two nesting levels: garden → object → plop. No recursive containers.
• API and DB are metric-only; cm ↔ ft/in conversion is purely a frontend display concern.

Editor / rendering

• Plain SVG in React. Tens of objects + low-hundreds of plops is far below SVG's ceiling; native DOM hit-testing, Tailwind styling, crisp text at any zoom. No Konva/canvas.
• One gesture library: @use-gesture/react for unified drag / wheel-zoom / pinch on desktop + touch. Everything else is hand-rolled pointer math.
• Viewport = a single <g transform="translate(tx,ty) scale(s)">; state {tx, ty, scale} where scale = px per cm. Wheel/pinch zooms to cursor; drag on empty space pans; drag on an element moves it.
• Field view and bed interior are the same canvas. "Click into a bed" animates the viewport to fit the object and sets focusedObjectId (mirrored to ?focus= URL param for deep links). Focused mode dims siblings and enables plop placement; Escape/tap-out zooms back.
• Semantic zoom, three bands by scale (thresholds tuned by feel):
  • zoomed out (< ~0.75 px/cm): plops render as flat color patches; plantable objects show name + dominant-plant color — "what's planted where" at a glance;
  • mid: plops as colored circles with the plant's emoji icon;
  • zoomed in (> ~3 px/cm): icon + plant name + count per plop.

API

REST under /api/v1, JSON, cookie-session auth (HttpOnly, SameSite=Lax, Secure under TLS). Gin with slog-gin + Recovery; embedded SPA fallback for non-/api routes.

POST /auth/register | /auth/login | /auth/logout     GET /auth/me      GET /auth/providers
GET  /auth/oidc/login      GET /auth/oidc/callback   (authorization-code + PKCE)
GET,POST /gardens                                    GET,PATCH,DELETE /gardens/:id
GET  /gardens/:id/full        ← one-shot editor load: garden + objects + plantings + referenced plants
GET  /gardens/:id/history     ← change sets, newest first (paginated)
POST /change-sets/:id/revert  ← undo an operation; 201, or 409 + the conflicts it skipped
POST /gardens/:id/copy        ← deep-copy a garden you own (objects + active plops; not shares/link)
POST /gardens/:id/objects     PATCH,DELETE /objects/:id
POST /objects/:id/plantings   PATCH,DELETE /plantings/:id
GET,POST /plants              PATCH,DELETE /plants/:id            (own plants only)
GET,POST /gardens/:id/shares  PATCH,DELETE /gardens/:id/shares/:userId    (invite by email)

Sync: plain REST + optimistic UI + last-write-wins with a version guard. Every PATCH/DELETE carries the row's version; the server increments on write and returns 409 + the current row on mismatch; the client rolls back and refetches. No websockets/CRDT — the right cost for household-scale co-editing. Drags PATCH once on drop, not per frame.

Backend layout

Storage: modernc.org/sqlite (pure Go) + hand-written SQL via database/sql. WAL mode + busy_timeout=5000 (open pattern per executus contrib/store/sqlite.go). Migrations are numbered .sql files in an embed.FS with a tiny runner and a schema_migrations(version) table, run at startup; seed plants live in a migration.

cmd/pansy/main.go        config load → store.Open → migrate → service → api → ListenAndServe
internal/config/         PANSY_PORT, PANSY_DB, PANSY_BASE_URL, PANSY_REGISTRATION,
                         PANSY_OIDC_* (issuer/client_id/secret/button label), PANSY_LOCAL_AUTH,
                         trusted proxies
internal/store/          sqlite.go (open/pragmas), migrate.go, migrations/*.sql (embedded),
                         queries per entity (users.go, gardens.go, objects.go, plantings.go,
                         plants.go, shares.go)
internal/domain/         plain structs + sentinel errors (ErrNotFound, ErrForbidden,
                         ErrVersionConflict)
internal/service/        ★ THE SEAM. All permission checks + business ops. auth.go, gardens.go,
                         objects.go, plantings.go, plants.go, shares.go, ops.go (FillRegion etc.),
                         revisions.go (change-set scoping, recording, revert)
internal/api/            thin gin handlers (decode → service → encode), session middleware,
                         ginserver setup, routes.go, oidc.go, spa.go (embed fallback)
internal/webdist/        dist.go: //go:embed all:dist   (web build copied in by Makefile)
internal/agent/          later: llm.DefineTool[Args] wrappers over the SAME service methods
web/                     Vite app
Makefile                 (cd web && npm run build) → copy dist → CGO_ENABLED=0 go build

Every mutation is recorded. Service mutations call record(...), which joins the change set on the context if one is open and otherwise opens a single-op one for that mutation alone. That auto-scope is what keeps undo shallow: REST handlers need no changes at all, and only the agent wraps a whole turn (WithChangeSet) so a multi-step turn undoes as one unit. A multi-row operation passes all its changes in one record call for the same reason.

The service seam is the point. Every operation is a method on *service.Service taking (ctx, actorUserID, args); all ACL checks live there, not in handlers. REST handlers are thin adapters; future agent tools are equally thin llm.DefineTool[Args] adapters over the same methods — so agent calls inherit permission enforcement for free. Bulk ops designed for agents from the start, e.g. FillRegion(ctx, actor, objectID, region, plantID, spacingOverride) with region a rect/circle in object-local coordinates.

Auth

• OIDC (primary; Authentik). github.com/coreos/go-oidc/v3 + golang.org/x/oauth2 (pure Go). Authorization-code flow with PKCE + state cookie; issuer discovery from PANSY_OIDC_ISSUER; redirect URI derived from PANSY_BASE_URL. JIT provisioning on first login (the IdP gates access, so the registration flag doesn't apply); the email claim links to an existing local account if one matches, otherwise a user is created and stamped with oidc_issuer/oidc_subject.
• Local (fallback). argon2id (x/crypto/argon2, id variant), subtle.ConstantTimeCompare. Disable entirely with PANSY_LOCAL_AUTH=false for pure-Authentik deployments.
• Both paths end in the same pansy session cookie. GET /auth/providers tells the login page which methods to show.

Frontend layout

React 19 + TypeScript + Vite + Tailwind 4 (@tailwindcss/vite), @tanstack/react-router, @tanstack/react-query, zod for API parsing; dev proxy /api → Go server.

• Routes: /login, /register, /gardens (list), /gardens/:id (editor, ?focus=objectId), /plants (catalog). Auth guard on the router root via /auth/me.
• State: TanStack Query for all server state (editor keyed on gardens/:id/full; optimistic mutations with version-conflict rollback). One small Zustand store for ephemeral editor state only: viewport, selection, focused object, active tool, in-flight drag.
• Editor components (web/src/editor/): GardenCanvas (svg root + viewport g), useViewport (use-gesture pan/zoom/pinch), ObjectShape, PlopMarker (semantic-zoom branching), Palette (drag-to-place object kinds), Inspector (side panel; bottom sheet on mobile), PlantPicker. Pure geometry helpers (local↔world transforms, unit formatting) in web/src/lib/geometry.ts, unit-tested.

Roadmap

1. Scaffold — Go module, config, gin server, healthz, sqlite + migration runner; Vite/Tailwind/router shell; embed.FS single-binary build.
2. Auth — OIDC (Authentik) + local fallback, sessions, route guard.
3. Gardens — CRUD + list page; establishes service-layer and version/409 conventions.
4. Field editor — objects, canvas, pan/zoom/pinch, palette, move/resize/rotate, optimistic sync. Riskiest slice — test on a phone at the end of it, not later.
5. Plant catalog — ~30 seeded built-ins + custom plants.
6. Plops — focus-zoom, place/move/resize, derived counts, semantic zoom. The core vision lands here.
7. Sharing — invite by email, roles, viewer read-only mode.
8. Polish — imperial toggle, mobile ergonomics, clear-bed, keyboard nudging.
9. Agent seam — ops.go bulk ops + internal/agent DefineTool wrappers; optional mort-style API-key agent endpoint. The agent harness itself lives in majordomo/executus, outside pansy.

Deliberate v1 limits

1. Plop count derived from area ÷ spacing², explicit override allowed.
2. Shapes: rect + circle only (polygon reserved in schema).
3. Seasons = planted/removed dates; a scenario/year-plan layer is future work these dates don't block.
4. Emoji plant icons (zero assets); SVG icon set later if wanted.
5. No background/satellite image tracing (cheap to add later as a garden background field).
6. 409-and-refetch conflict handling; no real-time sync.