/*
 * Copyright 2008 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.javascript.jscomp;

import com.google.javascript.rhino.Node;

/**
 * Tests for {@link DeadAssignmentsElimination}.
 *
 */
public class DeadAssignmentsEliminationTest extends CompilerTestCase {

  public DeadAssignmentsEliminationTest() {
    super("var extern;");
  }

  @Override
  public void setUp() {
    super.enableLineNumberCheck(true);
  }

  @Override
  public CompilerPass getProcessor(final Compiler compiler) {
    return new CompilerPass() {
      @Override
      public void process(Node externs, Node js) {
        NodeTraversal.traverse(
            compiler, js, new DeadAssignmentsElimination(compiler));
      }
    };
  }

  @Override
  protected int getNumRepetitions() {
    return 1;
  }

  public void testSimple() {
    inFunction("var a; a=1", "var a; 1");
    inFunction("var a; a=1+1", "var a; 1+1");
    inFunction("var a; a=foo();", "var a; foo()");
    inFunction("a=1; var a; a=foo();", "1; var a; foo();");
    // This should be: "var a; (function f(){})", but we don't mess with
    // functions with inner functions.
    inFunction("var a; a=function f(){}");
  }

  public void testLoops() {
    inFunction("for(var a=0; a<10; a++) {}");
    inFunction("var x; for(var a=0; a<10; a++) {x=a}; a(x)");
    inFunction("var x; for(var a=0; x=a<10; a++) {}",
        "var x; for(var a=0; a<10; a++) {}");
    inFunction("var x; for(var a=0; a<10; x=a) {}",
        "var x; for(var a=0; a<10; a) {}");
    inFunction("var x; for(var a=0; a<10; x=a,a++) {}",
        "var x; for(var a=0; a<10; a,a++) {}");
    inFunction("var x; for(var a=0; a<10; a++,x=a) {}",
        "var x; for(var a=0; a<10; a++,a) {}");
    inFunction("var x;for(var a=0; a<10; a++) {x=1}",
        "var x;for(var a=0; a<10; a++) {1}");
    inFunction("var x; x=1; do{x=2}while(0); x",
        "var x; 1; do{x=2}while(0); x");
    inFunction("var x; x=1; while(1){x=2}; x");
  }

  public void testMultiPaths() {
    inFunction("var x,y; if(x)y=1;", "var x,y; if(x)1;");
    inFunction("var x,y; if(x)y=1; y=2; x(y)", "var x,y; if(x)1; y=2; x(y)");
    inFunction("var x; switch(x) { case(1): x=1; break; } x");
    inFunction("var x; switch(x) { case(1): x=1; break; }",
        "var x; switch(x) { case(1): 1; break; }");
  }

  public void testUsedAsConditions() {
    inFunction("var x; while(x=1){}", "var x; while(1){}");
    inFunction("var x; if(x=1){}", "var x; if(1){}");
    inFunction("var x; do{}while(x=1)", "var x; do{}while(1)");
    inFunction("var x; if(x=1==4&&1){}", "var x; if(1==4&&1) {}");
    inFunction("var x; if(0&&(x=1)){}", "var x; if(0&&1){}");
    inFunction("var x; if((x=2)&&(x=1)){}", "var x; if(2&&1){}");
    inFunction("var x; x=2; if(0&&(x=1)){}; x");

    inFunction("var x,y; if( (x=1)+(y=2) > 3){}",
        "var x,y; if( 1+2 > 3){}");
  }

  public void testUsedAsConditionsInSwitchStatements() {
    inFunction("var x; switch(x=1){}","var x; switch(1){}");
    inFunction("var x; switch(x){case(x=1):break;}",
        "var x; switch(x){case(1):break;}");

    inFunction("var x,y; switch(y) { case (x += 1): break; case (x): break;}");

    inFunction("var x,y; switch(y) { case (x = 1): break; case (2): break;}",
               "var x,y; switch(y) { case (1): break; case (2): break;}");
    inFunction("var x,y; switch(y) { case (x+=1): break; case (x=2): break;}",
               "var x,y; switch(y) { case (x+1): break; case (2): break;}");
  }

  public void testAssignmentInReturn() {
    inFunction("var x; return x = 1;", "var x; return 1");
    inFunction("var x; return");
  }

  public void testAssignmentSamples() {
    // We want this to be "var x" in these cases.
    inFunction("var x = 2;");
    inFunction("var x = 2; x++;", "var x=2; void 0");
    inFunction("var x; x=x++;", "var x;x++");
    inFunction("var x; x+=1;", "var x;x+1");
  }

  public void testAssignmentInArgs() {
    inFunction("var x; foo(x = 1);", "var x; foo(1);");
    inFunction("var x; return foo(x = 1);", "var x; return foo(1);");
  }

  /**
   * BUG #1358904
   */
  public void testAssignAndReadInCondition() {
    inFunction("var a, b; if ((a = 1) && (b = a)) {b}");
    inFunction("var a, b; if ((b = a) && (a = 1)) {b}",
               "var a, b; if ((b = a) && (1)) {b}");
  }

  public void testParameters() {
    inFunction("param1=1; param1=2; param2(param1)",
        "1; param1=2; param2(param1)");
    inFunction("param1=param2()", "param2()");
  }

  public void testErrorHandling() {
    inFunction("var x; try{ x=1 } catch(e){ x=2 }; x");
    inFunction("var x; try{ x=1 } catch(e){ x=2 }",
        "var x;try{ 1 } catch(e) { 2 }");
    inFunction("var x; try{ x=1 } finally { x=2 }; x",
        "var x;try{ 1 } finally{ x=2 }; x");
    inFunction("var x; while(1) { try{x=1;break}finally{x} }");
    inFunction("var x; try{throw 1} catch(e){x=2} finally{x}");
    inFunction("var x; try{x=1;throw 1;x} finally{x=2}; x",
        "var x; try{1;throw 1;x} finally{x=2}; x");
  }

  public void testDeadVarDeclarations() {
    // Dead assignments in VAR is _NOT_ supported yet.
    inFunction("var x=1;");
    inFunction("var x=1; x=2; x");
  }

  public void testGlobal() {
    // Doesn't do any work on global scope yet.
    test("var x; x=1; x=2; x=3;", "var x; x=1; x=2; x=3;");
  }

  public void testInnerFunctions() {
    inFunction("var x = function() { var x; x=1; }",
        "var x = function() { var x; 1; }");
  }

  public void testInnerFunctions2() {
    // Give up DCE if there is a inner function.
    inFunction("var x = 0; print(x); x = 1; var y = function(){}; y()");
  }

  public void testSelfReAssignment() {
    inFunction("var x; x = x;", "var x; x");
  }

  public void testSelfIncrement() {
    inFunction("var x; x = x + 1;", "var x; x + 1");
  }

  public void testAssignmentOp() {
    // We have remove constant expressions that cleans this one up.
    inFunction("var x; x += foo()", "var x; x + foo()");
  }

  public void testAssignmentOpUsedAsLhs() {
    inFunction("var x,y; y = x += foo(); print(y)",
               "var x,y; y = x +  foo(); print(y)");
  }

  public void testAssignmentOpUsedAsCondition() {
    inFunction("var x; if(x += foo()) {}",
               "var x; if(x +  foo()) {}");

    inFunction("var x; if((x += foo()) > 1) {}",
               "var x; if((x +  foo()) > 1) {}");

    // Not in a while because this happens every loop.
    inFunction("var x; while((x += foo()) > 1) {}");

    inFunction("var x; for(;--x;){}");
    inFunction("var x; for(;x--;){}");
    inFunction("var x; for(;x -= 1;){}");
    inFunction("var x; for(;x = 0;){}", "var x; for(;0;){}");

    inFunction("var x; for(;;--x){}");
    inFunction("var x; for(;;x--){}");
    inFunction("var x; for(;;x -= 1){}");
    inFunction("var x; for(;;x = 0){}", "var x; for(;;0){}");

    inFunction("var x; for(--x;;){}", "var x; for(;;){}");
    inFunction("var x; for(x--;;){}", "var x; for(;;){}");
    inFunction("var x; for(x -= 1;;){}", "var x; for(x - 1;;){}");
    inFunction("var x; for(x = 0;;){}", "var x; for(0;;){}");
  }

  public void testDeadIncrement() {
    // TODO(user): Optimize this.
    inFunction("var x; x ++", "var x; void 0");
    inFunction("var x; x --", "var x; void 0");
  }

  public void testDeadButAlivePartiallyWithinTheExpression() {
    inFunction("var x; x = 100, print(x), x = 101;",
               "var x; x = 100, print(x),     101;");
    inFunction("var x; x = 100, print(x), print(x), x = 101;",
               "var x; x = 100, print(x), print(x),     101;");
    inFunction("var x; x = 100, print(x), x = 0, print(x), x = 101;",
               "var x; x = 100, print(x), x = 0, print(x),     101;");
  }

  public void testMutipleDeadAssignmentsButAlivePartiallyWithinTheExpression() {
    inFunction("var x; x = 1, x = 2, x = 3, x = 4, x = 5," +
               "  print(x), x = 0, print(x), x = 101;",

               "var x; 1, 2, 3, 4, x = 5, print(x), x = 0, print(x), 101;");
  }


  public void testDeadPartiallyWithinTheExpression() {
    // Sadly, this is not covered. We don't suspect this would happen too
    // often.
    inFunction("var x; x = 100, x = 101; print(x);");
  }

  public void testAssignmentChain() {
    inFunction("var a,b,c,d,e; a = b = c = d = e = 1",
               "var a,b,c,d,e; 1");
    inFunction("var a,b,c,d,e; a = b = c = d = e = 1; print(c)",
               "var a,b,c,d,e;         c = 1        ; print(c)");
    inFunction("var a,b,c,d,e; a = b = c = d = e = 1; print(a + e)",
               "var a,b,c,d,e; a =             e = 1; print(a + e)");
    inFunction("var a,b,c,d,e; a = b = c = d = e = 1; print(b + d)",
               "var a,b,c,d,e;     b =     d     = 1; print(b + d)");
    inFunction("var a,b,c,d,e; a = b = c = d = e = 1; print(a + b + d + e)",
               "var a,b,c,d,e; a = b =     d = e = 1; print(a + b + d + e)");
    inFunction("var a,b,c,d,e; a = b = c = d = e = 1; print(a+b+c+d+e)");
  }

  public void testAssignmentOpChain() {
    inFunction("var a,b,c,d,e; a = b = c += d = e = 1",
               "var a,b,c,d,e;         c + 1");
    inFunction("var a,b,c,d,e; a = b = c += d = e = 1;  print(e)",
               "var a,b,c,d,e;         c +     (e = 1); print(e)");
    inFunction("var a,b,c,d,e; a = b = c += d = e = 1;  print(d)",
               "var a,b,c,d,e;         c + (d = 1)  ;   print(d)");
    inFunction("var a,b,c,d,e; a = b = c += d = e = 1;  print(a)",
               "var a,b,c,d,e; a =     c +          1;  print(a)");
  }

  public void testIncDecInSubExpressions() {
    inFunction("var a; a = 1, a++; a");
    inFunction("var a; a = 1, ++a; a");
    inFunction("var a; a = 1, a--; a");
    inFunction("var a; a = 1, --a; a");

    inFunction("var a; a = 1, a++, print(a)");
    inFunction("var a; a = 1, ++a, print(a)");
    inFunction("var a; a = 1, a--, print(a)");
    inFunction("var a; a = 1, --a, print(a)");

    inFunction("var a; a = 1, print(a++)");
    inFunction("var a; a = 1, print(++a)");

    inFunction("var a; a = 1, print(a++)");
    inFunction("var a; a = 1, print(++a)");

    inFunction("var a; a = 1, print(a--)");
    inFunction("var a; a = 1, print(--a)");
  }

  public void testNestedReassignments() {
    inFunction("var a; a = (a = 1)", "var a; 1");
    inFunction("var a; a = (a *= 2)", "var a; a*2");

    // Note a = (a++) is not same as a++. Only if 'a' is dead.
    inFunction("var a; a = (a++)", "var a; a++"); // Preferred: "var a"
    inFunction("var a; a = (++a)", "var a; ++a"); // Preferred: "var a"

    inFunction("var a; a = (b = (a = 1))", "var a; b = 1");
    inFunction("var a; a = (b = (a *= 2))", "var a; b = a * 2");
    inFunction("var a; a = (b = (a++))", "var a; b=a++");
    inFunction("var a; a = (b = (++a))", "var a; b=++a");

    // Include b as local.
    inFunction("var a,b; a = (b = (a = 1))", "var a,b; 1");
    inFunction("var a,b; a = (b = (a *= 2))", "var a,b; a * 2");
    inFunction("var a,b; a = (b = (a++))",
               "var a,b; a++"); // Preferred: "var a,b"
    inFunction("var a,b; a = (b = (++a))",
               "var a,b; ++a"); // Preferred: "var a,b"

    inFunction("var a; a += (a++)", "var a; a + a++");
    inFunction("var a; a += (++a)", "var a; a+ (++a)");

    // Include b as local.
    inFunction("var a,b; a += (b = (a = 1))", "var a,b; a + 1");
    inFunction("var a,b; a += (b = (a *= 2))", "var a,b; a + (a * 2)");
    inFunction("var a,b; a += (b = (a++))", "var a,b; a + a++");
    inFunction("var a,b; a += (b = (++a))", "var a,b; a+(++a)");
  }

  public void testIncrementalReassignmentInForLoops() {
    inFunction("for(;x+=1;x+=1) {}");
    inFunction("for(;x;x+=1){}");
    inFunction("for(;x+=1;){foo(x)}");
    inFunction("for(;1;x+=1){foo(x)}");
  }

  public void testIdentityAssignments() {
    inFunction("var x; x=x", "var x; x");
  }

  private void inFunction(String src) {
    inFunction(src, src);
  }

  private void inFunction(String src, String expected) {
    test("function FUNC(param1, param2){" + src + "}",
         "function FUNC(param1, param2){" + expected + "}");
  }

  public void testBug8730257() {
    inFunction(
        "  try {" +
        "     var sortIndices = {};" +
        "     sortIndices = bar();" +
        "     for (var i = 0; i < 100; i++) {" +
        "       var sortIndex = sortIndices[i];" +
        "       bar(sortIndex);" +
        "     }" +
        "   } finally {" +
        "     bar();" +
        "   }" );
  }

  public void testAssignToExtern() {
    inFunction("extern = true;");
  }

  public void testIssue297a() {
    testSame("function f(p) {" +
         " var x;" +
         " return ((x=p.id) && (x=parseInt(x.substr(1))) && x>0);" +
         "}; f('');");
  }

  public void testIssue297b() {
    test("function f() {" +
         " var x;" +
         " return (x='') && (x = x.substr(1));" +
         "};",
         "function f() {" +
         " var x;" +
         " return (x='') && (x.substr(1));" +
         "};");
  }

  public void testIssue297c() {
    test("function f() {" +
         " var x;" +
         " return (x=1) && (x = f(x));" +
         "};",
         "function f() {" +
         " var x;" +
         " return (x=1) && f(x);" +
         "};");
  }

  public void testIssue297d() {
    test("function f(a) {" +
         " return (a=1) && (a = f(a));" +
         "};",
         "function f(a) {" +
         " return (a=1) && (f(a));" +
         "};");
  }

  public void testIssue297e() {
    test("function f(a) {" +
         " return (a=1) - (a = g(a));" +
         "};",
         "function f(a) {" +
         " return (a=1) - (g(a));" +
         "};");
  }

  public void testIssue297f() {
    test("function f(a) {" +
         " h((a=1) - (a = g(a)));" +
         "};",
         "function f(a) {" +
         " h((a=1) - (g(a)));" +
         "};");
  }

  public void testIssue297g() {
    test("function f(a) {" +
         " var b = h((b=1) - (b = g(b)));" +
         " return b;" +
         "};",
         // The last assignment in the initializer should be eliminated
         "function f(a) {" +
         " var b = h((b=1) - (b = g(b)));" +
         " return b;" +
         "};");
  }

  public void testIssue297h() {
    test("function f(a) {" +
         " var b = b=1;" +
         " return b;" +
         "};",
         // The assignment in the initializer should be eliminated
         "function f(a) {" +
         " var b = b = 1;" +
         " return b;" +
         "};");
  }


  public void testInExpression1() {
    inFunction("var a; return a=(a=(a=3));", "var a; return 3;");
    inFunction("var a; return a=(a=(a=a));", "var a; return a;");
    inFunction("var a; return a=(a=(a=a+1)+1);", "var a; return a+1+1;");
    inFunction("var a; return a=(a=(a=f(a)+1)+1);", "var a; return f(a)+1+1;");
    inFunction("var a; return a=f(a=f(a=f(a)));", "var a; return f(f(f(a)));");
  }

  public void testInExpression2() {
    // This can be improved.  "a = 1" is dead but "a" is read in the following
    // expression.
    inFunction(
        "var a; a = 1; if ((a = 2) || (a = 3) || (a)) {}",
        "var a; a = 1; if ((    2) || (a = 3) || (a)) {}");

    inFunction(
        "var a; (a = 1) || (a = 2)",
        "var a; 1 || 2");

    inFunction("var a; (a = 1) || (a = 2); return a");

    inFunction(
        "var a; a = 1; a ? a = 2 : a;",
        "var a; a = 1; a ?     2 : a;");

    inFunction("var a; a = 1; a ? a = 2 : a; return a");

    inFunction(
        "var a; a = 1; a ? a : a = 2;",
        "var a; a = 1; a ? a : 2;");

    inFunction("var a; a = 1; a ? a : a =2; return a");

    inFunction(
        "var a; (a = 1) ? a = 2 : a = 3;",
        "var a;      1  ?     2 :     3;");

    // This can be improved.  "a = 1" is dead but "a" is read in the following
    // expression.
    inFunction("var a; (a = 1) ? a = 2 : a = 3; return a");
  }

  public void testIssue384a() {
    inFunction(
            " var a, b;\n" +
            " if (f(b = true) || f(b = false))\n" +
            "   a = b;\n" +
            " else\n" +
            "   a = null;\n" +
            " return a;");
  }

  public void testIssue384b() {
    inFunction(
            " var a, b;\n" +
            " (f(b = true) || f(b = false)) ? (a = b) : (a = null);\n" +
            " return a;");
  }

  public void testIssue384c() {
    inFunction(
            " var a, b;\n" +
            " (a ? f(b = true) : f(b = false)) && (a = b);\n" +
            " return a;");
  }

  public void testIssue384d() {
    inFunction(
            " var a, b;\n" +
            " (f(b = true) || f(b = false)) && (a = b);\n" +
            " return a;");
  }

  public void testForIn() {
    inFunction("var x = {}; for (var y in x) { y() }");
    inFunction("var x, y, z; x = {}; z = {}; for (y in x = z) { y() }",
               "var x, y, z;   ({}); z = {}; for (y in z)     { y() }");
    inFunction("var x, y, z; x = {}; z = {}; for (y[z=1] in z) { y() }",
               "var x, y, z;   ({}); z = {}; for (y[z=1] in z) { y() }");

    // "x in z" doesn't overwrite x if z is empty.
    // TODO(user): If you look outside of just liveness, x = {} is dead.
    // That probably requires value numbering or SSA to detect that case.
    inFunction("var x, y, z; x = {}; z = {}; for (x in z) { x() }");
  }
}