package com.seaofnodes.simple;

import com.seaofnodes.simple.codegen.*;
import com.seaofnodes.simple.node.FunNode;
import com.seaofnodes.simple.type.Type;
import com.seaofnodes.simple.type.TypeFunPtr;
import com.seaofnodes.simple.type.Field;
import com.seaofnodes.simple.type.TypeInteger;
import com.seaofnodes.simple.util.Ary;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.BitSet;
import java.util.Comparator;
import java.util.Map;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.TestRule;
import org.junit.runners.model.Statement;
import static org.junit.Assert.*;

public class ClassInitDependenciesTest {
    private final ArrayList<Path> dirs = new ArrayList<>();

    @Rule public final TestRule cleanup = (test, description) -> new Statement() {
        @Override public void evaluate() throws Throwable {
            // Keep all fixtures if compilation or any later assertion fails.
            test.evaluate();
            for( Path dir : dirs ) {
                Path[] files;
                try( var paths=Files.walk(dir) ) {
                    files=paths.sorted(Comparator.reverseOrder()).toArray(Path[]::new);
                }
                for( Path file : files ) Files.delete(file);
            }
        }
    };

    private Path tempDir(String prefix) throws Exception {
        Path build=Path.of("build/init-deps");
        Files.createDirectories(build);
        Path dir=Files.createTempDirectory(build,prefix);
        dirs.add(dir);
        return dir;
    }

    private CodeGen compile(String entry, Map<String,String> sources, long seed) throws Exception {
        Path root=tempDir("case-");
        Files.writeString(root.resolve("Root.smp"),"val entry="+entry+";");
        for( var source : sources.entrySet() ) {
            Path path=root.resolve("Root/"+source.getKey()+".smp");
            Files.createDirectories(path.getParent());
            Files.writeString(path,source.getValue());
        }
        return new CodeGen(root.toString(),root.resolve("obj").toString(),null,
                           "Root",null,seed,true,TypeInteger.BOT).driver(CodeGen.Phase.TypeCheck);
    }

    private void cycle(String entry, Map<String,String> sources, String expected) throws Exception {
        expected="Root."+expected.replace(" -> "," -> Root.");
        for( long seed : new long[]{1,123,987654321} ) {
            try { compile(entry,sources,seed); fail("Expected initialization cycle"); }
            catch( Parser.ParseException ex ) {
                assertCycle(ex.getMessage(),expected);
            }
        }
    }

    // The cycle can start at any member, but must follow dependency direction.
    private void assertCycle(String message, String expected) {
        String prefix="Cyclic class initialization: ";
        assertTrue(message,message.startsWith(prefix));
        String actual=message.substring(prefix.length()).trim();
        String[] path=expected.split(" -> ");
        for( int start=0; start<path.length-1; start++ ) {
            ArrayList<String> rotated=new ArrayList<>();
            for( int i=0; i<path.length; i++ ) rotated.add(path[(start+i)%(path.length-1)]);
            if( actual.equals(String.join(" -> ",rotated)) ) return;
        }
        fail("Expected cycle "+expected+" (up to rotation), got "+actual);
    }

    // Follow ordinary helpers, stopping at the next initializer. This checks
    // the class prerequisite relation without requiring a total init order.
    private boolean touches(CodeGen code, ClassInitDependencies deps, String from, String to) {
        int src=code.link(code._compunits.get(from)).sig().fidx();
        int dst=code.link(code._compunits.get(to)).sig().fidx();
        return touches(code,deps._edgess,src,dst,new BitSet());
    }

    private boolean touches(CodeGen code, int[][] edges, int src, int dst, BitSet seen) {
        if( src>=edges.length || seen.get(src) || edges[src]==null ) return false;
        seen.set(src);
        for( int edge : edges[src] ) {
            if( edge==dst ) return true;
            FunNode fun=code.link(edge);
            if( fun!=null && !fun.isClz() && touches(code,edges,edge,dst,seen) ) return true;
        }
        return false;
    }

    @Test public void testEdgesAndPassiveReferences() throws Exception {
        CodeGen code = compile("A",Map.of("A","int value=B.value;", "B","int value=arg|1;"),123);
        ClassInitDependencies deps=new ClassInitDependencies(code);
        assertTrue(touches(code,deps,"Root/A","Root/B"));
        code=compile("A",Map.of("A","val b=B;", "B","val a=A;"),123);
        deps=new ClassInitDependencies(code);
        assertFalse(touches(code,deps,"Root/A","Root/B"));
        assertFalse(touches(code,deps,"Root/B","Root/A"));
        assertTrue(touches(code,deps,"Root/A","Root"));
        assertTrue(touches(code,deps,"Root/B","Root"));
    }

    @Test public void testCycles() throws Exception {
        cycle("A",Map.of("A","val get_noInline={ ->\n  B.value;\n};\nint value=get_noInline();",
                          "B","int value=A.value;"),"A -> B -> A");
        cycle("A",Map.of("A","int value=B.value;", "B","int value=A.value;"),"A -> B -> A");
        cycle("A",Map.of("A","val get={ -> B.value; }; int value=get();",
                          "B","int value=A.value;"),"A -> B -> A");
        cycle("A",Map.of("A","int value=get(); val get={ -> B.value; };",
                          "B","int value=A.value;"),"A -> B -> A");
        cycle("A",Map.of("A","int value=0; if(arg) value=B.value;",
                          "B","int value=A.value;"),"A -> B -> A");
        cycle("A",Map.of("A","val f=arg ? { -> B.value; } : { -> 0; }; int value=f();",
                          "B","int value=A.value;"),"A -> B -> A");
        cycle("P",Map.of("P","int value=A.value;", "P/A","int value=arg;"),"P -> P.A -> P");
    }

    @Test public void testSiblingsAndNonreturningCall() throws Exception {
        cycle("P",Map.of("P","val a=A; val b=B;", "P/A","int value=B.value;",
                          "P/B","int value=A.value;"),"P.A -> P.B -> P.A");
        cycle("A",Map.of("A","val get={ -> val x=B.value; while(1) {} return x; }; int value=get();",
                          "B","int value=A.value;"),"A -> B -> A");
        // An out-of-line nonreturning call retains its continuation's touches.
        cycle("A",Map.of(
            "A","int value=1; val stop_noInline={ -> while(1) {} return 1; }; stop_noInline(); return B.value;",
            "B","int value=A.value;"),"A -> B -> A");
        String source="val stop_noInline={ -> while(1) {} return 1; }; stop_noInline(); return 2;";
        CodeGen code=new CodeGen(source).driver(CodeGen.Phase.TypeCheck);
        assertNull(Eval2.eval(code,0,10)); // Evaluation reaches its loop budget.
        for( String cpu : new String[]{"x86_64_v2","arm","riscv"} )
            new CodeGen(source).driver(CodeGen.Phase.Encoding,cpu,"SystemV");
    }

    @Test public void testOptimizedDependencies() throws Exception {
        for( long seed : new long[]{1,123,987654321} ) {
            // SCCP learns this condition from a call; the parser cannot decide it.
            CodeGen code=compile("A",Map.of(
                "A","val test_noInline={ -> false; }; int value=1; if(test_noInline()) value=B.value;",
                "B","int value=A.value;"),seed);
            ClassInitDependencies deps=new ClassInitDependencies(code);
            assertFalse(touches(code,deps,"Root/A","Root/B"));
            assertTrue(touches(code,deps,"Root/B","Root/A"));

            code=compile("A",Map.of(
                "A","val test_noInline={ -> false; }; val f=test_noInline() ? { -> B.value; } : { -> 1; }; int value=f();",
                "B","int value=A.value;"),seed);
            assertFalse(touches(code,new ClassInitDependencies(code),"Root/A","Root/B"));

            // An unused helper's body must not become an initializer dependency.
            code=compile("A",Map.of("A","val unused={ -> B.value; }; int value=1;",
                                    "B","int value=A.value;"),seed);
            assertFalse(touches(code,new ClassInitDependencies(code),"Root/A","Root/B"));
        }
        // Discarding the value of a field read cannot discard its active touch.
        cycle("A",Map.of("A","int value=1; B.value; return 0;",
                          "B","int value=2; A.value; return 0;"),"A -> B -> A");
    }

    @Test public void testRecursionAndNativeCalls() throws Exception {
        CodeGen code=compile("A",Map.of("A","val f={int n -> n ? f(n-1) : B.value; }; int value=f(arg);",
                                       "B","int value=arg|1;"),123);
        assertTrue(touches(code,new ClassInitDependencies(code),"Root/A","Root/B"));
        code=compile("A",Map.of("A","{int} native=\"C\"; return native();"),123);

        Path dir=tempDir("import-");
        new CodeGen(null,dir.toString(),null,"B","int value=1;",123,true,TypeInteger.BOT)
            .driver(TestC.CPU_PORT,TestC.CALL_CONVENTION,false,false);
        code=new CodeGen(null,dir.toString(),new Ary<>(new String[]{dir.toString()}),
                         "A","return B.value;",123,true,TypeInteger.BOT).driver(CodeGen.Phase.TypeCheck);
        assertTrue(touches(code,new ClassInitDependencies(code),"A","B"));
    }

    private CodeGen object(Path dir, Path imports, String name, String source) {
        return new CodeGen(null,dir.toString(),new Ary<>(new String[]{imports.toString()}),
                           name,source,123,true,TypeInteger.BOT)
            .driver(TestC.CPU_PORT,TestC.CALL_CONVENTION,false,false);
    }

    private CodeGen module(Path dir, Path imports, String name, Map<String,String> sources) throws Exception {
        Path src=tempDir("import-");
        for( var entry : sources.entrySet() ) {
            Path file=src.resolve(entry.getKey()+".smp");
            Files.createDirectories(file.getParent());
            Files.writeString(file,entry.getValue());
        }
        return new CodeGen(src.toString(),dir.toString(),new Ary<>(new String[]{imports.toString()}),
            name,null,123,true,TypeInteger.BOT).driver(TestC.CPU_PORT,TestC.CALL_CONVENTION,false,false);
    }

    @Test public void testImportedInitialization() throws Exception {
        Path dir=tempDir("import-"), stubs=tempDir("import-");
        object(stubs,stubs,"A","int value=arg;");
        object(stubs,stubs,"B","int value=arg;");
        // Each object is independently acyclic. Combining their real bodies
        // must recheck the graph rather than trust either object's local order.
        object(dir,stubs,"A","int value=arg;\nvalue=B.value;");
        object(dir,stubs,"B","int value=arg; value=A.value;");
        for( String entry : new String[]{"A","B"} ) {
            try {
                new CodeGen(null,dir.toString(),new Ary<>(new String[]{dir.toString()}),
                            "Main","return "+entry+".value;",123,true,TypeInteger.BOT).driver(CodeGen.Phase.TypeCheck);
                fail("Expected imported initialization cycle");
            } catch( Parser.ParseException ex ) {
                assertCycle(ex.getMessage(),"A -> B -> A");
            }
        }
    }

    @Test public void testImportedDiamondAndHelpers() throws Exception {
        Path diamond=tempDir("import-");
        CodeGen dcode=object(diamond,diamond,"D","int value=arg;");
        var data=dcode._encoding._data.entries().stream().filter(obj -> obj.symbol.equals("D.$class")).findFirst().orElseThrow();
        var dclz=dcode._compunits.get("D")._clz;
        assertEquals(0,dcode._encoding._sdata.buf()[data.offset+dclz.offset(dclz.find("$init"))]);
        object(diamond,diamond,"B","int value=D.value;");
        object(diamond,diamond,"C","int value=D.value;");
        for( long seed : new long[]{1,123,987654321} ) {
            CodeGen code=new CodeGen(null,diamond.toString(),new Ary<>(new String[]{diamond.toString()}),
                "Main","int value=B.value+C.value;",seed,true,TypeInteger.BOT).driver(CodeGen.Phase.TypeCheck);
            CompUnit b=code._compunits.get("B"), d=code._compunits.get("D");
            ClassInitDependencies deps=new ClassInitDependencies(code);
            assertTrue(touches(code,deps,"B","D"));
            assertTrue(touches(code,deps,"C","D"));
            assertTrue(touches(code,deps,"Main","B"));
            assertTrue(touches(code,deps,"Main","C"));
            Field flag=d._clz.field("$init");
            assertSame(TypeInteger.U1,flag._t);
            assertFalse(flag._final);
            assertNotEquals(flag._alias,b._clz.field("$init")._alias);
            // Loading just the header/types uses the same alias identity and
            // does not require allocating any graph nodes.
            ElfReader elf=ElfReader.load(diamond.resolve("D.o").toFile(),d);
            assertEquals(flag._alias,elf.loadPublicTypes(code).field("$init")._alias);
            assertNull(elf._nodes);
        }
        object(diamond,diamond,"Helper","val get={ -> D.value; }; val get_noInline={ -> D.value; };");
        for( String name : new String[]{"get","get_noInline"} ) {
            CodeGen code=new CodeGen(null,diamond.toString(),new Ary<>(new String[]{diamond.toString()}),
                "Main","return Helper."+name+"();",123,true,TypeInteger.BOT).driver(CodeGen.Phase.TypeCheck);
            ClassInitDependencies deps=new ClassInitDependencies(code);
            assertTrue(touches(code,deps,"Main","D"));
            assertFalse(touches(code,deps,"Helper","D"));
        }
        object(diamond,diamond,"Wrapper","val get_noInline={ -> Helper.get_noInline(); };");
        CodeGen wrapped=new CodeGen(null,diamond.toString(),new Ary<>(new String[]{diamond.toString()}),
            "Main","return Wrapper.get_noInline();",123,true,TypeInteger.BOT).driver(CodeGen.Phase.TypeCheck);
        assertTrue(touches(wrapped,new ClassInitDependencies(wrapped),"Main","D"));
    }

    @Test public void testInterleavedModules() throws Exception {
        // Two objects, each providing a parent and children. Their orders
        // must interleave: P.B precedes Q.A, which precedes P.A.
        Path modules=tempDir("import-"), qstub=tempDir("import-");
        module(qstub,qstub,"Q",Map.of("Q","val A=A;", "Q/A","int value=arg;"));
        module(modules,qstub,"P",Map.of("P","val A=A; val B=B;",
            "P/A","int value=arg; value=Q.A.value;", "P/B","int value=arg;"));
        module(modules,modules,"Q",Map.of("Q","val A=A;", "Q/A","int value=arg; value=P.B.value;"));
        CodeGen combined=new CodeGen(null,modules.toString(),new Ary<>(new String[]{modules.toString()}),
            "Main","return P.A.value;",123,true,TypeInteger.BOT).driver(CodeGen.Phase.TypeCheck);
        ClassInitDependencies deps=new ClassInitDependencies(combined);
        assertTrue(touches(combined,deps,"Q/A","P/B"));
        assertTrue(touches(combined,deps,"P/A","Q/A"));
    }

    @Test public void testCycleReportDirection() throws Exception {
        cycle("A",Map.of("A","int value=B.value;", "B","int value=C.value;",
                          "C","int value=A.value;"),"A -> B -> C -> A");
    }

    @Test public void testOverlappingFunctionAndClassCycles() {
        // Fixed function graph: Opto/inlining must not erase the overlap that
        // exercises SCC traversal. f -> g -> f is legal; f -> A -> g -> f isn't.
        CodeGen code=new CodeGen("return 0;").driver(CodeGen.Phase.Opto);
        CompUnit cu=code._compunits.get("Test");
        code._linker.clear();
        String[] names={"f", "g", "A.<clinit>"};
        for( int i=0; i<names.length; i++ ) {
            TypeFunPtr sig=TypeFunPtr.make1((byte)2,false,new Type[0],TypeInteger.BOT,i+2);
            FunNode fun=new FunNode(null,sig,names[i],cu);
            fun._type=Type.CONTROL;
            code._linker.setX(i+2,fun);
        }
        ClassInitDependencies deps=new ClassInitDependencies(code);
        deps._edgess[2]=new int[]{3}; // f -> g
        deps._edgess[3]=new int[]{2}; // g -> f
        assertNull("Ordinary mutual recursion is legal",deps.check());
        deps._edgess[4]=new int[]{3}; // A -> g
        deps._edgess[2]=new int[]{3,4};
        String forward=deps.check();
        deps._edgess[2]=new int[]{4,3};
        String reverse=deps.check();
        assertTrue("Both successor orders must reject the class cycle: "+forward+", "+reverse,
                   forward!=null && reverse!=null);
    }
}