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-cnf.js

@@ -0,0 +1,172 @@
+"use strict";
+
+function collectRanges(exp, ranges = new Map()) {
+  if (["AND", "OR", "NOT"].includes(exp[0]))
+    for (let i = 1; i < exp.length; ++i) collectRanges(exp[i], ranges);
+  else if ([">", ">=", "<", "<=", "=", "<>"].includes(exp[0]))
+    if (!Array.isArray(exp[2])) {
+      const key = `${JSON.stringify(exp[1])}:${typeof exp[2]}`;
+      let s = ranges.get(key);
+      if (!s) ranges.set(key, (s = new Set()));
+      s.add(exp[2]);
+    } else if (!Array.isArray(exp[1])) {
+      const key = `${JSON.stringify(exp[2])}:${typeof exp[1]}`;
+      let s = ranges.get(key);
+      if (!s) ranges.set(key, (s = new Set()));
+      s.add(exp[2]);
+    }
+
+  return ranges;
+}
+
+function or(cnf1, cnf2) {
+  if (cnf1.length === 0) return cnf2;
+  else if (cnf2.length === 0) return cnf1;
+
+  const res = [];
+  for (let i = 0; i < cnf1.length; ++i)
+    for (let j = i; j < cnf2.length; ++j) res.push(cnf1[i].concat(cnf2[j]));
+
+  return res;
+}
+
+function booleanCnf(exp) {
+  const ranges = collectRanges(exp);
+  for (let [k, v] of ranges)
+    if (k.endsWith(":number"))
+      ranges.set(k, Array.from(v).sort((a, b) => a - b));
+    else ranges.set(k, Array.from(v).sort());
+
+  const expressions = new Map();
+  const mutuallyExclusive = new Map();
+
+  function getVariable(lhs, op, rhs = "") {
+    const key = `${lhs}:${op}:${rhs}`;
+    let f = expressions.get(key);
+    if (!f) {
+      expressions.set(key, (f = expressions.size + 1));
+      let m = mutuallyExclusive.get(lhs);
+      if (!m) mutuallyExclusive.set(lhs, (m = new Set()));
+      m.add(f);
+      if (rhs || key !== "null") m.add(getVariable(lhs, "null"));
+    }
+    return f;
+  }
+
+  function getComparisonVariables(lhs, from, fromInclusive, to, toInclusive) {
+    const type = from != null ? typeof from : typeof to;
+    const range = ranges.get(`${lhs}:${type}`);
+    const vars = [];
+
+    if (from == null) vars.push(`${lhs}:--${range[0]}`);
+    if (to == null) vars.push(`${lhs}:${range[range.length - 1]}--`);
+    if (fromInclusive) vars.push(`${lhs}:${from}`);
+    if (toInclusive) vars.push(`${lhs}:${to}`);
+
+    for (let i = 1; i < range.length; ++i)
+      if ((from == null || range[i] > from) && (to == null || range[i] <= to)) {
+        vars.push(`${lhs}:${range[i - 1]}`);
+        vars.push(`${lhs}:${range[i]}`);
+        vars.push(`${lhs}:${range[i - 1]}--${range[i]}`);
+      }
+
+    return vars.map(key => {
+      let f = expressions.get(key);
+      if (!f) {
+        expressions.set(key, (f = expressions.size + 1));
+        let m = mutuallyExclusive.get(lhs);
+        if (!m) mutuallyExclusive.set(lhs, (m = new Set()));
+        m.add(f);
+      }
+      return f;
+    });
+  }
+
+  const comparisonOperators = {
+    "=": v => [v, true, v, true],
+    ">": v => [v, false, null, null],
+    ">=": v => [v, true, null, null],
+    "<": v => [null, null, v, false],
+    "<=": v => [null, null, v, true]
+  };
+
+  function recursive(clause, negate) {
+    let op = clause[0];
+
+    if ((op === "AND" && !negate) || (op === "OR" && negate)) {
+      let res = [];
+      for (let i = 1; i < clause.length; ++i)
+        res = res.concat(recursive(clause[i], negate));
+      return res;
+    } else if ((op === "OR" && !negate) || (op === "AND" && negate)) {
+      let res = [];
+      for (let i = 1; i < clause.length; ++i)
+        res = or(res, recursive(clause[i], negate));
+      return res;
+    } else if (op === "NOT") {
+      return recursive(clause[1], !negate);
+    } else if (op === "<>") {
+      const vars = getComparisonVariables(
+        JSON.stringify(clause[1]),
+        ...comparisonOperators["="](clause[2])
+      );
+      if (!negate) return vars.map(x => [0 - x]);
+      else return [vars];
+    } else if (op === "IS NULL") {
+      const v = getVariable(JSON.stringify(clause[1]), "null");
+      if (negate) return [[0 - v]];
+      else return [[v]];
+    } else if (op === "IS NOT NULL") {
+      const v = getVariable(JSON.stringify(clause[1]), "null");
+      if (!negate) return [[0 - v]];
+      else return [[v]];
+    } else if (op in comparisonOperators) {
+      if (!Array.isArray(clause[2])) {
+        const vars = getComparisonVariables(
+          JSON.stringify(clause[1]),
+          ...comparisonOperators[op](clause[2])
+        );
+        if (negate) return vars.map(x => [0 - x]);
+        else return [vars];
+      } else if (!Array.isArray(clause[1])) {
+        op = { ">": "<", ">=": "<=", "<": ">", "<=": ">=" }[op] || op;
+        const vars = getComparisonVariables(
+          JSON.stringify(clause[2]),
+          ...comparisonOperators[op](clause[1])
+        );
+        if (negate) return vars.map(x => [0 - x]);
+        else return [vars];
+      } else {
+        let lhs = JSON.stringify(clause[1]);
+        let rhs = JSON.stringify(clause[2]);
+        // For consistency
+        if (rhs > lhs) {
+          let t = rhs;
+          rhs = lhs;
+          lhs = t;
+          op = { ">": "<", ">=": "<=", "<": ">", "<=": ">=" }[op] || op;
+        }
+
+        const v = getVariable(lhs, op, rhs);
+        if (negate) return [[0 - v]];
+        else return [[v]];
+      }
+    } else {
+      const v = getVariable(JSON.stringify(clause), "");
+      if (negate) return [[0 - v]];
+      else return [[v]];
+    }
+  }
+
+  const cnf = recursive(exp, false);
+
+  for (let m of mutuallyExclusive.values()) {
+    let ar = Array.from(m);
+    for (let i = 0; i < ar.length; ++i)
+      for (let j = i + 1; j < ar.length; ++j) cnf.push([0 - ar[i], 0 - ar[j]]);
+  }
+
+  return { vars: expressions.size, clauses: cnf };
+}
+
+exports.booleanCnf = booleanCnf;