Replace Filter class with expression structure

This is in order to be able to support UPPER() and LOWER() functions in
queries which are needed for case-insensitive search.

common/expression.js

@@ -0,0 +1,188 @@
+"use strict";
+
+const expressionParser = require("./expression-parser");
+const expressionCnf = require("./expression-cnf");
+const satSolver = require("./sat-solver");
+
+const isArray = Array.isArray;
+
+function* permute(arr) {
+  if (arr.length <= 1) {
+    for (let i = 0; i < arr[0]; ++i) yield [i];
+    return;
+  }
+
+  let slc = arr.slice(1);
+  for (let i = 0; i < arr[0]; ++i)
+    for (let innerArr of permute(slc)) yield [i].concat(innerArr);
+}
+
+function reduce(exp, callback) {
+  let loop = true;
+  while (loop) {
+    loop = false;
+    for (let i = 2; i < exp.length; ++i) {
+      let res = callback(exp[i - 1], exp[i]);
+      if (res !== undefined) {
+        loop = true;
+        exp = exp.slice();
+        exp.splice(i - 1, 2, res);
+      }
+    }
+  }
+  if (exp.length === 2) return exp[1];
+  return exp;
+}
+
+function evaluate(exp, obj, now) {
+  return expressionParser.map(exp, e => {
+    if (!isArray(e)) return e;
+
+    if (e[0] === "FUNC") {
+      if (e[1] === "NOW") {
+        if (now) return now;
+      } else if (e[1] === "UPPER") {
+        if (e[2] == null) return null;
+        if (!isArray(e[2])) return `${e[2]}`.toUpperCase();
+      } else if (e[1] === "LOWER") {
+        if (e[12] == null) return null;
+        if (!isArray(e[2])) return `${e[2]}`.toLowerCase();
+      }
+    } else if (e[0] === "PARAM") {
+      if (e[1] == null) return null;
+      if (obj && !isArray(e[1]))
+        if (typeof obj[e[1]] === "object")
+          return obj[e[1]].value ? obj[e[1]].value[0] : null;
+        else return obj[e[1]];
+    } else if (e[0] === "AND") {
+      return reduce(e, (a, b) => {
+        if (!isArray(a)) return a ? b : a;
+        if (!isArray(b)) return b ? a : b;
+      });
+    } else if (e[0] === "OR") {
+      return reduce(e, (a, b) => {
+        if (!isArray(a)) return a ? a : b;
+        if (!isArray(b)) return b ? b : a;
+      });
+    } else if (e[0] === "NOT") {
+      if (!isArray(e[1])) return !e[1];
+      else if (e[1][0] === "NOT") return e[1][1];
+    } else if (e[0] === "IS NULL") {
+      if (isArray(e[1])) return e;
+      return e[1] == null;
+    } else if (e[0] === "IS NOT NULL") {
+      if (isArray(e[1])) return e;
+      return e[1] != null;
+    } else if (e[0] === "=") {
+      if (isArray(e[1]) || isArray(e[2])) return e;
+      if (e[1] == null || e[2] == null) return null;
+      return e[1] === e[2];
+    } else if (e[0] === "<>") {
+      if (isArray(e[1]) || isArray(e[2])) return e;
+      if (e[1] == null || e[2] == null) return null;
+      return e[1] !== e[2];
+    } else if (e[0] === ">") {
+      if (isArray(e[1]) || isArray(e[2])) return e;
+      if (e[1] == null || e[2] == null) return null;
+      return e[1] > e[2];
+    } else if (e[0] === ">=") {
+      if (isArray(e[1]) || isArray(e[2])) return e;
+      if (e[1] == null || e[2] == null) return null;
+      return e[1] >= e[2];
+    } else if (e[0] === "<") {
+      if (isArray(e[1]) || isArray(e[2])) return e;
+      if (e[1] == null || e[2] == null) return null;
+      return e[1] < e[2];
+    } else if (e[0] === "<=") {
+      if (isArray(e[1]) || isArray(e[2])) return e;
+      if (e[1] == null || e[2] == null) return null;
+      return e[1] <= e[2];
+    } else if (e[0] === "*") {
+      return reduce(e, (a, b) => {
+        if (!isArray(a) && !isArray(b)) {
+          if (a == null || b == null) return null;
+          return a * b;
+        }
+      });
+    } else if (e[0] === "/") {
+      return reduce(e, (a, b) => {
+        if (!isArray(a) && !isArray(b)) {
+          if (a == null || b == null) return null;
+          return a / b;
+        }
+      });
+    } else if (e[0] === "+") {
+      return reduce(e, (a, b) => {
+        if (!isArray(a) && !isArray(b)) {
+          if (a == null || b == null) return null;
+          return a + b;
+        }
+      });
+    } else if (e[0] === "-") {
+      return reduce(e, (a, b) => {
+        if (!isArray(a) && !isArray(b)) {
+          if (a == null || b == null) return null;
+          return a - b;
+        }
+      });
+    } else if (e[0] === "||") {
+      return reduce(e, (a, b) => {
+        if (!isArray(a) && !isArray(b)) {
+          if (a == null || b == null) return null;
+          return `${a}${b}`;
+        }
+      });
+    }
+    return e;
+  });
+}
+
+function and(exp1, exp2) {
+  if (!isArray(exp1)) return exp1 ? exp2 : exp1;
+  if (!isArray(exp2)) return exp2 ? exp1 : exp2;
+
+  let res = ["AND"];
+
+  if (exp1[0] === "AND") res = res.concat(exp1.slice(1));
+  else res.push(exp1);
+
+  if (exp2[0] === "AND") res = res.concat(exp2.slice(1));
+  else res.push(exp2);
+
+  return res;
+}
+
+function or(exp1, exp2) {
+  if (!isArray(exp1)) return exp1 ? exp1 : exp2;
+  if (!isArray(exp2)) return exp2 ? exp2 : exp1;
+
+  let res = ["OR"];
+
+  if (exp1[0] === "OR") res = res.concat(exp1.slice(1));
+  else res.push(exp1);
+
+  if (exp2[0] === "OR") res = res.concat(exp2.slice(1));
+  else res.push(exp2);
+
+  return res;
+}
+
+function not(exp) {
+  if (isArray(exp) && exp[0] === "NOT") return exp[1];
+  return ["NOT", exp];
+}
+
+function subset(exp1, exp2) {
+  const e = evaluate(["NOT", ["OR", ["NOT", exp1], exp2]]);
+  if (!isArray(e)) return !e;
+  const { vars, clauses } = expressionCnf.booleanCnf(e);
+  return !satSolver.naiveDpll(clauses, vars);
+}
+
+exports.evaluate = evaluate;
+exports.and = and;
+exports.or = or;
+exports.not = not;
+exports.subset = subset;
+exports.parse = expressionParser.parse;
+exports.stringify = expressionParser.stringify;