1	import Base
2	import ./src/Keys.bend as Keys
3	import ./src/MemTable.bend as MemTable
4	import ./src/SortedRun.bend as SortedRun
5	import ./src/Sstable.bend as Sstable
6	import ./src/SstFile.bend as SstFile
7	import ./src/Wal.bend as Wal
8	import ./src/Manifest.bend as Manifest
9	import ./src/MergeIter.bend as MergeIter
10	import ./src/Db.bend as Db
11	
12	# --- Level 2: part control (1:1 delegates) ---
13	def cmp(+s1: String, +s2: String) -> Cmp:
14	  Keys.cmp(s1, s2)
15	
16	# Key equality: true exactly for identical strings.
17	def eq(+s1: String, +s2: String) -> Bool:
18	  Keys.eq(s1, s2)
19	
20	# Empty MemTable: no entries, count zero.
21	def mem_empty() -> MemTable.MemTable:
22	  MemTable.empty()
23	
24	# MemTable with one live version prepended (newest-first log).
25	def mem_put(tab: MemTable.MemTable, key: String, val: String) -> MemTable.MemTable:
26	  MemTable.put(tab, key, val)
27	
28	# MemTable with one tombstone prepended; hides older versions on read.
29	def mem_del(tab: MemTable.MemTable, key: String) -> MemTable.MemTable:
30	  MemTable.del(tab, key)
31	
32	# Newest-first read; a tombstone answers None and hides older versions.
33	def mem_get(tab: MemTable.MemTable, +key: String) -> Maybe<&2, String>:
34	  MemTable.get(tab, key)
35	
36	# Number of log entries, live and tombstoned.
37	def mem_count(tab: MemTable.MemTable) -> Nat:
38	  MemTable.count(tab)
39	
40	# Canonicalize newest-first entries into a strict ordered run.
41	def sort_newest(entries: List<&2, MemTable.Entry>) -> List<&2, MemTable.Entry>:
42	  SortedRun.sort_newest(entries)
43	
44	# Range scan over a merged run: lo <= key < hi, tombstones dropped.
45	def range_scan(+merged: List<&2, MemTable.Entry>, lo: String, hi: String) -> List<&2, MemTable.Entry>:
46	  MergeIter.scan(merged, lo, hi)
47	
48	# Build an SSTable, canonicalizing entries newest-first.
49	def sst_build(+entries: List<&2, MemTable.Entry>, level: Nat, est_keys: Nat) -> Sstable.Table:
50	  Sstable.build(entries, level, est_keys)
51	
52	# Build an SSTable trusting an already strict, unique run (no sorting).
53	def sst_from_sorted_unique(+entries: List<&2, MemTable.Entry>, level: Nat) -> Sstable.Table:
54	  Sstable.from_sorted_unique(entries, level)
55	
56	# Build an SSTable from a sorted run with an explicit key estimate.
57	def sst_build_sorted(+entries: List<&2, MemTable.Entry>, level: Nat, est_keys: Nat) -> Sstable.Table:
58	  Sstable.build_sorted(entries, level, est_keys)
59	
60	# Encode a WAL batch to its exact on-disk bytes.
61	def wal_encode(batch: Wal.Batch) -> String:
62	  Wal.encode(batch)
63	
64	# Decode WAL bytes; None on corrupt or truncated input (fail-closed).
65	def wal_decode(+str: String) -> Maybe<&2, Wal.Batch>:
66	  Wal.decode(str)
67	
68	# Serialize entries to the compact v2 table wire format.
69	def sst_serialize(+entries: List<&2, MemTable.Entry>, +level: Nat) -> String:
70	  SstFile.serialize(entries, level)
71	
72	# Parse v2 table bytes with checksum verification; None when rejected.
73	def sst_parse(+encoded: String) -> Maybe<&2, Sstable.Table>:
74	  SstFile.parse(encoded)
75	
76	# Serialize a Manifest to its exact on-disk bytes.
77	def mfst_serialize(mfst: Manifest.Manifest) -> String:
78	  Manifest.serialize(mfst)
79	
80	# Parse Manifest bytes; None on corrupt input (fail-closed).
81	def mfst_parse(+str: String) -> Maybe<&2, Manifest.Manifest>:
82	  Manifest.parse(str)
83	
84	# --- Level 1: Sess session monad (primary API) ---
85	type Sess<a, -A: Kind(a)> is Kind(a <&> &1):
86	  Sess{run: Db.Db -> (Db.Db & A)}
87	
88	def Sess.pure(a, -A: Kind(a), val: A) -> Sess<a, A>:
89	  Sess{db => (db, val)}
90	
91	def Sess.run_go(b, -B: Kind(b), sess: Sess<b, B>, st: Db.Db) -> Db.Db & B:
92	  match sess:
93	    case Sess{run}: run(st)
94	
95	def Sess.apply(a, -A: Kind(a), b, -B: Kind(b), pair: Db.Db & A, fun: A -> Sess<b, B>) -> Db.Db & B:
96	  match pair:
97	    case (st, x): Sess.run_go(b, B, fun(x), st)
98	
99	def Sess.bind(a, -A: Kind(a), -B: Kind(a), sess: Sess<a, A>, fun: A -> Sess<a, B>) -> Sess<a, B>:
100	  Sess{st => Sess.apply(a, A, a, B, Sess.run_go(a, A, sess, st), fun)}
101	
102	# Open a database handle over a directory label (pure; no IO touched).
103	def open(+dir: String) -> Db.Db:
104	  Db.open_db(dir)
105	
106	# Pure put transition used by the session action.
107	def put_go(+db: Db.Db, +key: String, +val: String) -> Db.Db:
108	  match db:
109	    case Db.Db{dir, mem, frozen, batch_cap, bcache, levels, flushed, manifest_token, mem_count, frozen_count}:
110	      Db.apply_done(Db.apply_and_rotate(Con{Wal.Put{key, val}, Nil{}}, mem, frozen, mem_count, frozen_count), dir, batch_cap, bcache, levels, flushed, manifest_token)
111	
112	# Pure delete transition used by the session action.
113	def del_go(+db: Db.Db, +key: String) -> Db.Db:
114	  match db:
115	    case Db.Db{dir, mem, frozen, batch_cap, bcache, levels, flushed, manifest_token, mem_count, frozen_count}:
116	      Db.apply_done(Db.apply_and_rotate(Con{Wal.Del{key}, Nil{}}, mem, frozen, mem_count, frozen_count), dir, batch_cap, bcache, levels, flushed, manifest_token)
117	
118	# Pure batch transition used by the session action.
119	def batch_go(+db: Db.Db, +muts: List<&2, Wal.Mut>) -> Db.Db:
120	  match db:
121	    case Db.Db{dir, mem, frozen, batch_cap, bcache, levels, flushed, manifest_token, mem_count, frozen_count}:
122	      Db.apply_done(Db.apply_and_rotate(muts, mem, frozen, mem_count, frozen_count), dir, batch_cap, bcache, levels, flushed, manifest_token)
123	
124	# Pure point-read transition used by the session action (cache-backed).
125	def sget_go(+db: Db.Db, +key: String) -> Db.Db & Maybe<&2, String>:
126	  Db.db_get_cached(db, key)
127	
128	# Session step writing one key.
129	def sput(+key: String, +val: String) -> Sess<&2, Unit>:
130	  Sess{db => (put_go(db, key, val), Unit{})}
131	
132	# Session step deleting one key.
133	def sdel(+key: String) -> Sess<&2, Unit>:
134	  Sess{db => (del_go(db, key), Unit{})}
135	
136	# Session step applying a whole mutation batch at once.
137	def sbatch(+muts: List<&2, Wal.Mut>) -> Sess<&2, Unit>:
138	  Sess{db => (batch_go(db, muts), Unit{})}
139	
140	# Session step reading one key.
141	def sget(+key: String) -> Sess<&2, Maybe<&2, String>>:
142	  Sess{db => sget_go(db, key)}
143	
144	# Execute a whole session against a handle.
145	def run_sess(a, -A: Kind(a), st: Db.Db, sess: Sess<a, A>) -> Db.Db & A:
146	  Sess.run_go(a, A, sess, st)
147	
148	# Project the answer out of a runner pair.
149	def value_of(a, -A: Kind(a), pair: Db.Db & A) -> A:
150	  match pair:
151	    case (db, x): x
152	
153	# Render the exact WAL bytes a VFS adapter frames with wal_frame plus fsync.
154	def encode_batch(batch: Wal.Batch) -> String:
155	  Wal.encode(batch)