DiunDashboard/.planning/phases/02-backend-refactor/02-01-SUMMARY.md

---
phase: 02-backend-refactor
plan: "01"
subsystem: database
tags: [golang-migrate, sqlite, store-interface, dependency-injection, migrations, embed-fs]

# Dependency graph
requires:
  - phase: 01-data-integrity
    provides: PRAGMA foreign_keys enforcement and UPSERT semantics in existing diunwebhook.go
provides:
  - Store interface with 9 methods covering all persistence operations
  - SQLiteStore implementing Store with exact SQL from current handlers
  - RunMigrations function using golang-migrate + embed.FS (iofs source)
  - Baseline migration 0001 with full current schema (CREATE TABLE IF NOT EXISTS)
affects:
  - 02-02 (Server struct refactor will use Store interface and RunMigrations)
  - 03-postgresql (PostgreSQLStore will implement same Store interface)

# Tech tracking
tech-stack:
  added:
    - github.com/golang-migrate/migrate/v4 v4.19.1
    - github.com/golang-migrate/migrate/v4/database/sqlite (modernc.org/sqlite driver, no CGO)
    - github.com/golang-migrate/migrate/v4/source/iofs (embed.FS migration source)
  patterns:
    - Store interface pattern - persistence abstraction hiding *sql.DB from handlers
    - SQLiteStore with per-struct sync.Mutex (replaces package-level global)
    - golang-migrate with embedded SQL files via //go:embed migrations/sqlite
    - ErrNoChange guard in RunMigrations (startup idempotency)
    - CREATE TABLE IF NOT EXISTS in baseline migration (backward compatible with existing databases)

key-files:
  created:
    - pkg/diunwebhook/store.go
    - pkg/diunwebhook/sqlite_store.go
    - pkg/diunwebhook/migrate.go
    - pkg/diunwebhook/migrations/sqlite/0001_initial_schema.up.sql
    - pkg/diunwebhook/migrations/sqlite/0001_initial_schema.down.sql
  modified:
    - go.mod
    - go.sum

key-decisions:
  - "Used database/sqlite sub-package (not database/sqlite3) to avoid CGO - confirmed modernc.org/sqlite usage in sqlite.go source"
  - "Single 0001 baseline migration with full schema including acknowledged_at - safe for existing databases via CREATE TABLE IF NOT EXISTS"
  - "NewSQLiteStore sets MaxOpenConns(1) and PRAGMA foreign_keys = ON - moved from InitDB which will be removed in Plan 02"
  - "AssignTag preserves INSERT OR REPLACE (not ON CONFLICT DO UPDATE) per research Pitfall 6 - correct semantics for tag_assignments PRIMARY KEY"
  - "defer rows.Close() directly (not verbose closure pattern) as plan specifies"

patterns-established:
  - "Store interface: all persistence behind 9 named methods, no *sql.DB in interface signature"
  - "SQLiteStore field mutex: sync.Mutex as struct field, not package global - enables parallel test isolation"
  - "Migration files: versioned SQL files embedded via //go:embed, applied via golang-migrate at startup"
  - "ErrNoChange is not an error: errors.Is(err, migrate.ErrNoChange) guard ensures idempotent startup"

requirements-completed: [REFAC-01, REFAC-03]

# Metrics
duration: 6min
completed: "2026-03-23"
---

# Phase 02 Plan 01: Store Interface and Migration Infrastructure Summary

**Store interface (9 methods) + SQLiteStore implementation + golang-migrate v4.19.1 migration infrastructure with embedded SQL files**

## Performance

- **Duration:** ~6 min
- **Started:** 2026-03-23T20:50:31Z
- **Completed:** 2026-03-23T20:56:56Z
- **Tasks:** 2
- **Files modified:** 7

## Accomplishments

- Store interface with 9 methods extracted from current handler SQL (UpsertEvent, GetUpdates, AcknowledgeUpdate, ListTags, CreateTag, DeleteTag, AssignTag, UnassignTag, TagExists)
- SQLiteStore implementing all 9 Store methods with exact SQL semantics preserved from diunwebhook.go
- golang-migrate v4.19.1 migration infrastructure with RunMigrations using embed.FS and iofs source
- Baseline migration 0001 with full current schema using CREATE TABLE IF NOT EXISTS (safe for existing databases)
- All existing tests pass; no existing code modified (additive-only changes as specified)

## Task Commits

Each task was committed atomically:

1. **Task 1: Create Store interface and SQLiteStore implementation** - `57bf3bd` (feat)
2. **Task 2: Create migration infrastructure and SQL files** - `6506d93` (feat)

**Plan metadata:** (docs commit follows)

## Files Created/Modified

- `pkg/diunwebhook/store.go` - Store interface with 9 persistence methods
- `pkg/diunwebhook/sqlite_store.go` - SQLiteStore struct implementing Store; NewSQLiteStore sets MaxOpenConns(1) and PRAGMA foreign_keys = ON
- `pkg/diunwebhook/migrate.go` - RunMigrations using golang-migrate + embed.FS + iofs; handles ErrNoChange
- `pkg/diunwebhook/migrations/sqlite/0001_initial_schema.up.sql` - Full baseline schema (updates, tags, tag_assignments) with CREATE TABLE IF NOT EXISTS
- `pkg/diunwebhook/migrations/sqlite/0001_initial_schema.down.sql` - DROP TABLE IF EXISTS for all three tables
- `go.mod` - Added github.com/golang-migrate/migrate/v4 v4.19.1 and sub-packages
- `go.sum` - Updated checksums

## Decisions Made

- Used `database/sqlite` (not `database/sqlite3`) for golang-migrate driver — confirmed at source level that it imports `modernc.org/sqlite`, satisfying no-CGO constraint
- Single 0001 baseline migration includes `acknowledged_at` from the start; safe for existing databases because `CREATE TABLE IF NOT EXISTS` makes it idempotent on pre-existing schemas
- `NewSQLiteStore` sets `MaxOpenConns(1)` and `PRAGMA foreign_keys = ON` — these will no longer live in `InitDB` once Plan 02 removes globals
- `AssignTag` uses `INSERT OR REPLACE` (not `ON CONFLICT DO UPDATE`) — preserves semantics per research Pitfall 6

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

- `go vet` reports a pre-existing issue in `diunwebhook_test.go:227` (`call to (*testing.T).Fatalf from a non-test goroutine`) — confirmed pre-existing before any changes; out of scope for this plan. Logged to deferred-items.
- `mattn/go-sqlite3` appears in `go mod graph` as an indirect dependency of the `golang-migrate` module itself, but our code only imports `database/sqlite` (confirmed no CGO import in our code chain via `go mod graph | grep sqlite3 | grep -v golang-migrate`).

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- Store interface and SQLiteStore ready for Plan 02 to wire into Server struct
- RunMigrations ready to call from main.go instead of InitDB
- All existing tests pass — Plan 02 can refactor handlers with confidence
- Blocker: Plan 02 must redesign export_test.go (currently references package-level globals that will be removed)

---
*Phase: 02-backend-refactor*
*Completed: 2026-03-23*