--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/sql_cache.sml	Tue Mar 25 02:04:06 2014 -0400
@@ -0,0 +1,179 @@
+structure SqlCache = struct
+
+open Sql
+open Mono
+
+structure IS = IntBinarySet
+structure IM = IntBinaryMap
+structure StringKey = struct type ord_key = string val compare = String.compare end
+structure SS = BinarySetFn (StringKey)
+structure SM = BinaryMapFn (StringKey)
+structure SIMM = MultimapFn (structure KeyMap = SM structure ValSet = IS)
+
+val rec tablesRead =
+ fn Query1 {From=tablePairs, ...} => SS.fromList (map #1 tablePairs)
+  | Union (q1,q2) => SS.union (tablesRead q1, tablesRead q2)
+
+val tableWritten =
+ fn Insert (tab, _) => tab
+  | Delete (tab, _) => tab
+  | Update (tab, _, _) => tab
+
+fun tablesInExp' exp' =
+    let
+        val nothing = {read = SS.empty, written = SS.empty}
+    in
+        case exp' of
+            EQuery {query=e, ...} =>
+            (case parse query e of
+                 SOME q => {read = tablesRead q, written = SS.empty}
+               | NONE => nothing)
+          | EDml (e, _) =>
+            (case parse dml e of
+                 SOME q => {read = SS.empty, written = SS.singleton (tableWritten q)}
+               | NONE => nothing)
+          | _ => nothing
+    end
+
+val tablesInExp =
+    let
+        fun addTables (exp', {read, written}) =
+            let val {read = r, written = w} = tablesInExp' exp'
+            in {read = SS.union (r, read), written = SS.union (w, written)} end
+    in
+        MonoUtil.Exp.fold {typ = #2, exp = addTables}
+                          {read = SS.empty, written = SS.empty}
+    end
+
+fun intExp (n, loc) = (EPrim (Prim.Int (Int64.fromInt n)), loc)
+fun intTyp loc = (TFfi ("Basis", "int"), loc)
+fun boolPat (b, loc) = (PCon (Enum,
+                              PConFfi {mod = "Basis", datatyp = "bool", arg = NONE,
+                                       con = if b then "True" else "False"},
+                              NONE),
+                        loc)
+fun boolTyp loc = (TFfi ("Basis", "int"), loc)
+
+fun ffiAppExp (module, func, arg, loc) =
+    (EFfiApp (module, func, [(intExp (arg, loc), intTyp loc)]), loc)
+
+fun sequence (befores, center, afters, loc) =
+    List.foldr (fn (exp, seq) => (ESeq (exp, seq), loc))
+               (List.foldl (fn (exp, seq) => (ESeq (seq, exp), loc))
+                           center
+                           afters)
+               befores
+
+fun antiguardUnit (cond, exp, loc) =
+    (ECase (cond,
+            [(boolPat (false, loc), exp),
+             (boolPat (true, loc), (ERecord [], loc))],
+            {disc = boolTyp loc, result = (TRecord [], loc)}),
+     loc)
+
+fun underAbs f (exp as (exp', loc)) =
+    case exp' of
+        EAbs (x, y, z, body) => (EAbs (x, y, z, underAbs f body), loc)
+      | _ => f exp
+
+fun addCacheCheck (index, exp) =
+    let
+        fun f (body as (_, loc)) =
+            let
+                val check = ffiAppExp ("Cache", "check", index, loc)
+                val store = ffiAppExp ("Cache", "store", index, loc)
+            in
+                antiguardUnit (check, sequence ([], body, [store], loc), loc)
+            end
+    in
+        underAbs f exp
+    end
+
+fun addCacheFlush (exp, tablesToIndices) =
+    let
+        fun addIndices (table, indices) = IS.union (indices, SIMM.find (tablesToIndices, table))
+        fun f (body as (_, loc)) =
+            let
+                fun mapFfi func = List.map (fn i => ffiAppExp ("Cache", func, i, loc))
+                val flushes =
+                    IS.listItems (SS.foldr addIndices IS.empty (#written (tablesInExp body)))
+
+            in
+                sequence (mapFfi "flush" flushes, body, mapFfi "ready" flushes, loc)
+            end
+    in
+        underAbs f exp
+    end
+
+val handlerIndices =
+    let
+        val isUnit =
+         fn (TRecord [], _) => true
+          | _ => false
+        fun maybeAdd (d, soFar as {readers, writers}) =
+            case d of
+                DExport (Link ReadOnly, _, name, typs, typ, _) =>
+                if List.all isUnit (typ::typs)
+                then {readers = IS.add (readers, name), writers = writers}
+                else soFar
+              | DExport (_, _, name, _, _, _) => (* Not read only. *)
+                {readers = readers, writers = IS.add (writers, name)}
+              | _ => soFar
+    in
+        MonoUtil.File.fold {typ = #2, exp = #2, decl = maybeAdd}
+                           {readers = IS.empty, writers = IS.empty}
+    end
+
+fun fileFoldMapiSelected f init (file, indices) =
+    let
+        fun doExp (original as ((a, index, b, exp, c), state)) =
+            if IS.member (indices, index)
+            then let val (newExp, newState) = f (index, exp, state)
+                 in ((a, index, b, newExp, c), newState) end
+            else original
+        fun doDecl decl state =
+            let
+                val result =
+                    case decl of
+                        DVal x =>
+                        let val (y, newState) = doExp (x, state)
+                        in (DVal y, newState) end
+                      | DValRec xs =>
+                        let val (ys, newState) = ListUtil.foldlMap doExp state xs
+                        in (DValRec ys, newState) end
+                      | _ => (decl, state)
+            in
+                Search.Continue result
+            end
+        fun nada x y = Search.Continue (x, y)
+    in
+        case MonoUtil.File.mapfold {typ = nada, exp = nada, decl = doDecl} file init of
+            Search.Continue x => x
+          | _ => (file, init) (* Should never happen. *)
+    end
+
+fun fileMapSelected f = #1 o fileFoldMapiSelected (fn (_, x, _) => (f x, ())) ()
+
+val addCacheChecking =
+    let
+        fun f (index, exp, tablesToIndices) =
+            (addCacheCheck (index, exp),
+             SS.foldr (fn (table, tsToIs) => SIMM.insert (tsToIs, table, index))
+                      tablesToIndices
+                      (#read (tablesInExp exp)))
+    in
+        fileFoldMapiSelected f (SM.empty)
+    end
+
+fun addCacheFlushing (file, tablesToIndices, writers) =
+    fileMapSelected (fn exp => addCacheFlush (exp, tablesToIndices)) (file, writers)
+
+fun go file =
+    let
+        val {readers, writers} = handlerIndices file
+        val (fileWithChecks, tablesToIndices) = addCacheChecking (file, readers)
+    in
+        addCacheFlushing (fileWithChecks, tablesToIndices, writers)
+    end
+
+end