src/Store.bend
ber-core-store@0.1.1.0 · 59 lines · 0 definitions
1import Base
2import mylsm-lsm-store@0.3.1.0/mylsm.bend as MyLsmStore
3import mylsm-lsm-store@0.3.1.0/src/Db.bend as DbTypes
4
5# Session effects for ber-core. Op is a newtype over MyLSM Sess and Handle
6# over MyLSM Db: ber-core names THESE types, and this module is the ONLY one
7# naming MyLSM. do-blocks desugar through Op.bind/Op.pure exactly like Sess.
8# Bend has no value projection: inner sessions unwrap via Op.inner (match on
9# the parameter), never `op.run`; computed pairs thread through helpers.
10
11# One session step chain; the answer type rides along.
12type Op<a, -A: Kind(a)> is Kind(a <&> &1):
13 Op{run: MyLsmStore.Sess<a, A>}
14
15# An opened store handle; affine, threaded through run_op.
16type Handle is Type:
17 Handle{db: DbTypes.Db}
18
19# Unwraps the inner session for translators like bind and run_op.
20def Op.inner(b, -B: Kind(b), op: Op<b, B>) -> MyLsmStore.Sess<b, B>:
21 match op:
22 case Op{inner_sess}:
23 inner_sess
24
25# Lifts a pure value; what `return` desugars to inside do-blocks.
26def Op.pure(a, -A: Kind(a), val: A) -> Op<a, A>:
27 Op{MyLsmStore.Sess.pure(a, A, val)}
28
29# Sequences two ops; what `<-` desugars to inside do-blocks.
30def Op.bind(a, -A: Kind(a), -B: Kind(a), op: Op<a, A>, fun: A -> Op<a, B>) -> Op<a, B>:
31 Op{MyLsmStore.Sess.bind(a, A, B, Op.inner(a, A, op), x => Op.inner(a, B, fun(x)))}
32
33# Writes one key.
34def oput(+key: String, +val: String) -> Op<&2, Unit>:
35 Op{MyLsmStore.sput(key, val)}
36
37# Reads one key; missing reads as None.
38def oget(+key: String) -> Op<&2, Maybe<&2, String>>:
39 Op{MyLsmStore.sget(key)}
40
41# Deletes one key.
42def odel(+key: String) -> Op<&2, Unit>:
43 Op{MyLsmStore.sdel(key)}
44
45# Opens a store handle over a directory label.
46def open_store(+dir: String) -> Handle:
47 Handle{MyLsmStore.open(dir)}
48
49# Rewraps a computed runner pair into Handle form.
50def rewrap_pair(a, -A: Kind(a), computed_pair: DbTypes.Db & A) -> Handle & A:
51 match computed_pair:
52 case (db_next, answer):
53 (Handle{db_next}, answer)
54
55# Executes a whole op chain against a handle.
56def run_op(a, -A: Kind(a), store: Handle, op: Op<a, A>) -> Handle & A:
57 match store:
58 case Handle{db}:
59 rewrap_pair(a, A, MyLsmStore.run_sess(a, A, db, Op.inner(a, A, op)))