#include <clang/AST/ASTContext.h>
#include <clang/AST/Decl.h>
#include <clang/AST/Expr.h>
#include <clang/AST/RecursiveASTVisitor.h>
#include <clang/Frontend/ASTUnit.h>
#include <clang/Tooling/Tooling.h>

#include <catch2/catch_test_macros.hpp>
#include <memory>
#include <string>
#include <vector>

#include "fold/symbolic/encoder_callee_names.hpp"

namespace {

std::unique_ptr<clang::ASTUnit> parse(const std::string& code) {
    return clang::tooling::buildASTFromCodeWithArgs(code, {"-std=c++20"}, "input.cpp");
}

const clang::FunctionDecl* functionNamed(clang::ASTUnit& unit, const std::string& qname) {
    const clang::FunctionDecl* found = nullptr;
    struct Visitor : clang::RecursiveASTVisitor<Visitor> {
        const std::string& target;
        const clang::FunctionDecl*& out;
        Visitor(const std::string& t, const clang::FunctionDecl*& o) : target(t), out(o) {}
        bool VisitFunctionDecl(clang::FunctionDecl* fd) {
            if (fd->hasBody() && fd->getQualifiedNameAsString() == target) {
                out = fd;
                return false;
            }
            return true;
        }
    } visitor(qname, found);
    visitor.TraverseDecl(unit.getASTContext().getTranslationUnitDecl());
    return found;
}

std::vector<const clang::CallExpr*> collectCalls(clang::ASTUnit& unit, const std::string& in_func) {
    std::vector<const clang::CallExpr*> calls;
    const clang::FunctionDecl* fd = functionNamed(unit, in_func);
    if (fd == nullptr || fd->getBody() == nullptr)
        return calls;
    struct Visitor : clang::RecursiveASTVisitor<Visitor> {
        std::vector<const clang::CallExpr*>& out;
        explicit Visitor(std::vector<const clang::CallExpr*>& o) : out(o) {}
        bool VisitCallExpr(clang::CallExpr* ce) {
            out.push_back(ce);
            return true;
        }
    } visitor(calls);
    visitor.TraverseStmt(fd->getBody());
    return calls;
}

} // namespace

TEST_CASE("calleeName returns the unqualified function name for a direct call",
          "[encoder][callee_names]") {
    auto unit = parse(R"cpp(
        void target(int);
        void caller() { target(1); }
    )cpp");
    REQUIRE(unit);

    auto calls = collectCalls(*unit, "caller");
    REQUIRE(calls.size() == 1);
    REQUIRE(fold::calleeName(calls[0]) == "target");
}

TEST_CASE("calleeName strips namespaces from the unqualified form", "[encoder][callee_names]") {
    auto unit = parse(R"cpp(
        namespace ns { void inner(); }
        void caller() { ns::inner(); }
    )cpp");
    REQUIRE(unit);

    auto calls = collectCalls(*unit, "caller");
    REQUIRE(calls.size() == 1);
    REQUIRE(fold::calleeName(calls[0]) == "inner");
}

TEST_CASE("calleeName extracts the method name from a C++ member call", "[encoder][callee_names]") {
    auto unit = parse(R"cpp(
        struct S { void method() {} };
        void caller() { S s; s.method(); }
    )cpp");
    REQUIRE(unit);

    auto calls = collectCalls(*unit, "caller");
    REQUIRE(!calls.empty());
    bool found_method_call = false;
    for (const auto* ce : calls) {
        if (fold::calleeName(ce) == "method")
            found_method_call = true;
    }
    REQUIRE(found_method_call);
}

TEST_CASE("calleeName returns empty for null", "[encoder][callee_names]") {
    REQUIRE(fold::calleeName(nullptr).empty());
}

TEST_CASE("qualifiedFunctionName returns the fully-qualified C++ name",
          "[encoder][callee_names][qualified]") {
    auto unit = parse(R"cpp(
        namespace outer { namespace inner { void target() {} } }
    )cpp");
    REQUIRE(unit);

    const clang::FunctionDecl* fd = functionNamed(*unit, "outer::inner::target");
    REQUIRE(fd);

    // External linkage: no @file suffix expected.
    const std::string name = fold::qualifiedFunctionName(fd);
    REQUIRE(name == "outer::inner::target");
}

TEST_CASE("qualifiedFunctionName appends file suffix for internal-linkage statics",
          "[encoder][callee_names][qualified][linkage]") {
    auto unit = parse(R"cpp(
        static int helper() { return 0; }
    )cpp");
    REQUIRE(unit);

    const clang::FunctionDecl* fd = functionNamed(*unit, "helper");
    REQUIRE(fd);

    const std::string name = fold::qualifiedFunctionName(fd);
    // Should be "helper@<path>" — the @-suffix is what disambiguates
    // same-named statics across TUs.
    REQUIRE(name.starts_with("helper@"));
    REQUIRE(name.find("input.cpp") != std::string::npos);
}

TEST_CASE("qualifiedFunctionName returns empty for null", "[encoder][callee_names][qualified]") {
    REQUIRE(fold::qualifiedFunctionName(nullptr).empty());
}

TEST_CASE("qualifiedCalleeName resolves through a direct CallExpr",
          "[encoder][callee_names][qualified]") {
    auto unit = parse(R"cpp(
        namespace ns { void target() {} }
        void caller() { ns::target(); }
    )cpp");
    REQUIRE(unit);

    auto calls = collectCalls(*unit, "caller");
    REQUIRE(calls.size() == 1);
    REQUIRE(fold::qualifiedCalleeName(calls[0]) == "ns::target");
}

TEST_CASE("qualifiedCalleeName returns empty for null", "[encoder][callee_names][qualified]") {
    REQUIRE(fold::qualifiedCalleeName(nullptr).empty());
}

TEST_CASE("isCLibraryCallee: only C library functions, never members or namespaced lookalikes",
          "[encoder-callee-names][library]") {
    auto unit = parse("extern \"C\" void free(void*);\n"
                      "namespace std { using ::free; }\n"
                      "namespace mine { void free(void*) {} }\n"
                      "struct Pool { void free(void*) {} };\n"
                      "void global_helper(void*) {}\n"
                      "void f(void* p, Pool& pool, void (*fp)(void*)) {\n"
                      "  free(p);\n"
                      "  std::free(p);\n"
                      "  mine::free(p);\n"
                      "  pool.free(p);\n"
                      "  global_helper(p);\n"
                      "  fp(p);\n"
                      "}\n");
    REQUIRE(unit);
    const auto calls = collectCalls(*unit, "f");
    REQUIRE(calls.size() == 6);
    CHECK(fold::isCLibraryCallee(calls[0]));       // ::free (extern "C")
    CHECK(fold::isCLibraryCallee(calls[1]));       // std::free resolves to ::free
    CHECK_FALSE(fold::isCLibraryCallee(calls[2])); // mine::free
    CHECK_FALSE(fold::isCLibraryCallee(calls[3])); // Pool::free
    CHECK_FALSE(fold::isCLibraryCallee(calls[4])); // global C++ function, not extern "C"
    CHECK_FALSE(fold::isCLibraryCallee(calls[5])); // indirect call
    CHECK_FALSE(fold::isCLibraryCallee(nullptr));
}