events.v

1//! Events: what Koh learns about saves that already exist.2//!3//! Save records are write-once, so a flag is not stored on the save. It is4//! appended as a small event that syncs alongside saves, and a save's flag5//! state is always derived from the newest event about it — never stored twice.6//! A strip event is what makes `strip` visible to other machines.78module events910import strings11import time12import src.machine13import src.storage1415pub const kind_flag = 'flag'16pub const kind_clear = 'clear'17pub const kind_strip = 'strip'1819// An event about one save.20pub struct Event {21pub mut:22	id         string23	kind       string24	save_id    string25	path       string26	reason     string27	created_at i6428	machine    string29}3031// Flag is the derived answer to "is this save flagged, and why".32pub struct Flag {33pub:34	save_id string35	flagged bool36	reason  string37	at      i6438}3940const select_event = 'SELECT id, kind, save_id, path, reason, created_at, machine FROM events'4142fn read_event(stmt &storage.Stmt) Event {43	return Event{44		id:         stmt.text(0)45		kind:       stmt.text(1)46		save_id:    stmt.text_or_none(2) or { '' }47		path:       stmt.text_or_none(3) or { '' }48		reason:     stmt.text_or_none(4) or { '' }49		created_at: stmt.int(5)50		machine:    stmt.text(6)51	}52}5354// write appends an event. The ID is the first 12 hex characters of the Blake355// hash of the record, so two machines that record the same fact agree.56pub fn write(store &storage.Store, event Event) !Event {57	mut record := event58	if record.created_at == 0 {59		// Events are ordered by time, and flag/clear can land in the same60		// second. Bumping past the newest event keeps "newest wins" true, and61		// keeps the ordering the same on every machine.62		record.created_at = next_timestamp(store)!63	}64	if record.machine == '' {65		record.machine = machine.name()66	}67	record.id = event_id(record)68	insert(store, record)!69	return record70}7172// write_once appends an event whose ID covers only what it says, not when it73// was said. Re-running an interrupted strip therefore records the same fact74// instead of a second one.75pub fn write_once(store &storage.Store, event Event) !Event {76	mut record := event77	if record.created_at == 0 {78		record.created_at = time.now().unix()79	}80	if record.machine == '' {81		record.machine = machine.name()82	}83	record.id = storage.hash_hex('${record.kind}:${record.save_id}:${record.path}'.bytes())[..12]84	insert(store, record)!85	return record86}8788fn next_timestamp(store &storage.Store) !i64 {89	now := time.now().unix()90	mut stmt := store.db.prepare('SELECT MAX(created_at) FROM events')!91	defer {92		stmt.finalize()93	}94	if !stmt.step()! {95		return now96	}97	newest := stmt.int_or_none(0) or { return now }98	if newest >= now {99		return newest + 1100	}101	return now102}103104fn insert(store &storage.Store, record Event) ! {105	mut stmt := store.db.prepare('INSERT OR IGNORE INTO events106		(id, kind, save_id, path, reason, created_at, machine) VALUES (?, ?, ?, ?, ?, ?, ?)')!107	defer {108		stmt.finalize()109	}110	stmt.bind_text(1, record.id)!111	stmt.bind_text(2, record.kind)!112	bind_optional(stmt, 3, record.save_id)!113	bind_optional(stmt, 4, record.path)!114	bind_optional(stmt, 5, record.reason)!115	stmt.bind_int(6, record.created_at)!116	stmt.bind_text(7, record.machine)!117	stmt.step()!118}119120pub fn flag(store &storage.Store, save_id string, reason string) !Event {121	return write(store, Event{122		kind:    kind_flag123		save_id: save_id124		reason:  reason125	})!126}127128pub fn clear_flag(store &storage.Store, save_id string) !Event {129	return write(store, Event{130		kind:    kind_clear131		save_id: save_id132	})!133}134135// strip records that a path was removed from a save (or from every save, when136// save_id is empty).137pub fn strip(store &storage.Store, save_id string, path string) !Event {138	return write_once(store, Event{139		kind:    kind_strip140		save_id: save_id141		path:    path142	})!143}144145pub fn event_id(event Event) string {146	mut sb := strings.Builder{}147	put(mut sb, 'kind', event.kind)148	put(mut sb, 'save', event.save_id)149	put(mut sb, 'path', event.path)150	put(mut sb, 'reason', event.reason)151	put(mut sb, 'created', event.created_at.str())152	put(mut sb, 'machine', event.machine)153	return storage.hash_hex(sb.str().bytes())[..12]154}155156fn put(mut sb strings.Builder, name string, value string) {157	sb.write_string('${name}:${value.len}:')158	sb.write_string(value)159	sb.write_string('\n')160}161162fn bind_optional(stmt &storage.Stmt, index int, value string) ! {163	if value == '' {164		stmt.bind_null(index)!165	} else {166		stmt.bind_text(index, value)!167	}168}169170// all returns every event, oldest first.171pub fn all(store &storage.Store) ![]Event {172	mut stmt := store.db.prepare('${select_event} ORDER BY created_at, id')!173	defer {174		stmt.finalize()175	}176	mut out := []Event{}177	for stmt.step()! {178		out << read_event(stmt)179	}180	return out181}182183// latest_flags derives the flag state of every save that has ever been flagged184// or cleared. Newest wins, ties broken by ID so the answer is the same on every185// machine.186pub fn latest_flags(store &storage.Store) !map[string]Flag {187	mut stmt := store.db.prepare('${select_event} WHERE kind IN (?, ?) AND save_id IS NOT NULL188		ORDER BY created_at, id')!189	defer {190		stmt.finalize()191	}192	stmt.bind_text(1, kind_flag)!193	stmt.bind_text(2, kind_clear)!194	mut flags := map[string]Flag{}195	for stmt.step()! {196		event := read_event(stmt)197		flags[event.save_id] = Flag{198			save_id: event.save_id199			flagged: event.kind == kind_flag200			reason:  event.reason201			at:      event.created_at202		}203	}204	return flags205}206207pub fn flag_state(store &storage.Store, save_id string) !Flag {208	flags := latest_flags(store)!209	return flags[save_id] or {210		Flag{211			save_id: save_id212		}213	}214}215216// flagged_ids is what the log and the history view mark.217pub fn flagged_ids(store &storage.Store) ![]string {218	flags := latest_flags(store)!219	mut ids := []string{}220	for save_id, state in flags {221		if state.flagged {222			ids << save_id223		}224	}225	ids.sort()226	return ids227}228229pub fn strip_events(store &storage.Store) ![]Event {230	mut stmt := store.db.prepare('${select_event} WHERE kind = ? ORDER BY created_at, id')!231	defer {232		stmt.finalize()233	}234	stmt.bind_text(1, kind_strip)!235	mut out := []Event{}236	for stmt.step()! {237		out << read_event(stmt)238	}239	return out240}