// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#include "Luau/RequireTracer.h"

#include "Luau/Ast.h"
#include "Luau/Module.h"

LUAU_FASTFLAGVARIABLE(LuauExtendedSimpleRequire)

namespace Luau
{

struct RequireTracer : AstVisitor
{
    RequireTracer(RequireTraceResult& result, FileResolver* fileResolver, const ModuleName& currentModuleName)
        : result(result)
        , fileResolver(fileResolver)
        , currentModuleName(currentModuleName)
        , locals(nullptr)
    {
    }

    bool visit(AstExprTypeAssertion* expr) override
    {
        // suppress `require() :: any`
        return false;
    }

    bool visit(AstExprCall* expr) override
    {
        AstExprGlobal* global = expr->func->as<AstExprGlobal>();

        if (global && global->name == "require" && expr->args.size >= 1)
            requireCalls.push_back(expr);

        return true;
    }

    bool visit(AstStatLocal* stat) override
    {
        for (size_t i = 0; i < stat->vars.size && i < stat->values.size; ++i)
        {
            AstLocal* local = stat->vars.data[i];
            AstExpr* expr = stat->values.data[i];

            // track initializing expression to be able to trace modules through locals
            locals[local] = expr;
        }

        return true;
    }

    bool visit(AstStatAssign* stat) override
    {
        for (size_t i = 0; i < stat->vars.size; ++i)
        {
            // locals that are assigned don't have a known expression
            if (AstExprLocal* expr = stat->vars.data[i]->as<AstExprLocal>())
                locals[expr->local] = nullptr;
        }

        return true;
    }

    bool visit(AstType* node) override
    {
        // allow resolving require inside `typeof` annotations
        return true;
    }

    AstExpr* getDependent_DEPRECATED(AstExpr* node)
    {
        if (AstExprLocal* expr = node->as<AstExprLocal>())
            return locals[expr->local];
        else if (AstExprIndexName* expr = node->as<AstExprIndexName>())
            return expr->expr;
        else if (AstExprIndexExpr* expr = node->as<AstExprIndexExpr>())
            return expr->expr;
        else if (AstExprCall* expr = node->as<AstExprCall>(); expr && expr->self)
            return expr->func->as<AstExprIndexName>()->expr;
        else
            return nullptr;
    }
    AstNode* getDependent(AstNode* node)
    {
        if (AstExprLocal* expr = node->as<AstExprLocal>())
            return locals[expr->local];
        else if (AstExprIndexName* expr = node->as<AstExprIndexName>())
            return expr->expr;
        else if (AstExprIndexExpr* expr = node->as<AstExprIndexExpr>())
            return expr->expr;
        else if (AstExprCall* expr = node->as<AstExprCall>(); expr && expr->self)
            return expr->func->as<AstExprIndexName>()->expr;
        else if (AstExprGroup* expr = node->as<AstExprGroup>())
            return expr->expr;
        else if (AstExprTypeAssertion* expr = node->as<AstExprTypeAssertion>())
            return expr->annotation;
        else if (AstTypeGroup* expr = node->as<AstTypeGroup>())
            return expr->type;
        else if (AstTypeTypeof* expr = node->as<AstTypeTypeof>())
            return expr->expr;
        else
            return nullptr;
    }

    void process()
    {
        ModuleInfo moduleContext{currentModuleName};

        if (FFlag::LuauExtendedSimpleRequire)
        {
            // seed worklist with require arguments
            work.reserve(requireCalls.size());

            for (AstExprCall* require : requireCalls)
                work.push_back(require->args.data[0]);

            // push all dependent expressions to the work stack; note that the vector is modified during traversal
            for (size_t i = 0; i < work.size(); ++i)
            {
                if (AstNode* dep = getDependent(work[i]))
                    work.push_back(dep);
            }

            // resolve all expressions to a module info
            for (size_t i = work.size(); i > 0; --i)
            {
                AstNode* expr = work[i - 1];

                // when multiple expressions depend on the same one we push it to work queue multiple times
                if (result.exprs.contains(expr))
                    continue;

                std::optional<ModuleInfo> info;

                if (AstNode* dep = getDependent(expr))
                {
                    const ModuleInfo* context = result.exprs.find(dep);

                    if (context && expr->is<AstExprLocal>())
                        info = *context; // locals just inherit their dependent context, no resolution required
                    else if (context && (expr->is<AstExprGroup>() || expr->is<AstTypeGroup>()))
                        info = *context; // simple group nodes propagate their value
                    else if (context && (expr->is<AstTypeTypeof>() || expr->is<AstExprTypeAssertion>()))
                        info = *context; // typeof type annotations will resolve to the typeof content
                    else if (AstExpr* asExpr = expr->asExpr())
                        info = fileResolver->resolveModule(context, asExpr);
                }
                else if (AstExpr* asExpr = expr->asExpr())
                {
                    info = fileResolver->resolveModule(&moduleContext, asExpr);
                }

                if (info)
                    result.exprs[expr] = std::move(*info);
            }
        }
        else
        {
            // seed worklist with require arguments
            work_DEPRECATED.reserve(requireCalls.size());

            for (AstExprCall* require : requireCalls)
                work_DEPRECATED.push_back(require->args.data[0]);

            // push all dependent expressions to the work stack; note that the vector is modified during traversal
            for (size_t i = 0; i < work_DEPRECATED.size(); ++i)
                if (AstExpr* dep = getDependent_DEPRECATED(work_DEPRECATED[i]))
                    work_DEPRECATED.push_back(dep);

            // resolve all expressions to a module info
            for (size_t i = work_DEPRECATED.size(); i > 0; --i)
            {
                AstExpr* expr = work_DEPRECATED[i - 1];

                // when multiple expressions depend on the same one we push it to work queue multiple times
                if (result.exprs.contains(expr))
                    continue;

                std::optional<ModuleInfo> info;

                if (AstExpr* dep = getDependent_DEPRECATED(expr))
                {
                    const ModuleInfo* context = result.exprs.find(dep);

                    // locals just inherit their dependent context, no resolution required
                    if (expr->is<AstExprLocal>())
                        info = context ? std::optional<ModuleInfo>(*context) : std::nullopt;
                    else
                        info = fileResolver->resolveModule(context, expr);
                }
                else
                {
                    info = fileResolver->resolveModule(&moduleContext, expr);
                }

                if (info)
                    result.exprs[expr] = std::move(*info);
            }
        }

        // resolve all requires according to their argument
        result.requireList.reserve(requireCalls.size());

        for (AstExprCall* require : requireCalls)
        {
            AstExpr* arg = require->args.data[0];

            if (const ModuleInfo* info = result.exprs.find(arg))
            {
                result.requireList.push_back({info->name, require->location});

                ModuleInfo infoCopy = *info; // copy *info out since next line invalidates info!
                result.exprs[require] = std::move(infoCopy);
            }
            else
            {
                result.exprs[require] = {}; // mark require as unresolved
            }
        }
    }

    RequireTraceResult& result;
    FileResolver* fileResolver;
    ModuleName currentModuleName;

    DenseHashMap<AstLocal*, AstExpr*> locals;
    std::vector<AstExpr*> work_DEPRECATED;
    std::vector<AstNode*> work;
    std::vector<AstExprCall*> requireCalls;
};

RequireTraceResult traceRequires(FileResolver* fileResolver, AstStatBlock* root, const ModuleName& currentModuleName)
{
    RequireTraceResult result;
    RequireTracer tracer{result, fileResolver, currentModuleName};
    root->visit(&tracer);
    tracer.process();
    return result;
}

} // namespace Luau
