// Copyright 2023 The Dawn & Tint Authors
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#include "src/tint/lang/glsl/writer/printer/printer.h"

#include <string>
#include <utility>

#include "src/tint/lang/core/ir/function.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/return.h"
#include "src/tint/lang/core/ir/unreachable.h"
#include "src/tint/lang/core/ir/validator.h"
#include "src/tint/lang/glsl/writer/common/version.h"
#include "src/tint/utils/generator/text_generator.h"
#include "src/tint/utils/macros/scoped_assignment.h"
#include "src/tint/utils/rtti/switch.h"

using namespace tint::core::fluent_types;  // NOLINT

namespace tint::glsl::writer {
namespace {

/// PIMPL class for the MSL generator
class Printer : public tint::TextGenerator {
  public:
    /// Constructor
    /// @param module the Tint IR module to generate
    explicit Printer(const core::ir::Module& module) : ir_(module) {}

    /// @param version the GLSL version information
    /// @returns the generated GLSL shader
    tint::Result<std::string> Generate(const Version& version) {
        auto valid = core::ir::ValidateAndDumpIfNeeded(ir_, "GLSL writer");
        if (!valid) {
            return std::move(valid.Failure());
        }

        {
            TINT_SCOPED_ASSIGNMENT(current_buffer_, &preamble_buffer_);

            auto out = Line();
            out << "#version " << version.major_version << version.minor_version << "0";
            if (version.IsES()) {
                out << " es";
            }
        }

        // Emit module-scope declarations.
        EmitBlockInstructions(ir_.root_block);

        // Emit functions.
        for (auto& func : ir_.functions) {
            EmitFunction(func);
        }

        StringStream ss;
        ss << preamble_buffer_.String() << '\n' << main_buffer_.String();
        return ss.str();
    }

  private:
    const core::ir::Module& ir_;

    /// The buffer holding preamble text
    TextBuffer preamble_buffer_;

    /// The current function being emitted
    const core::ir::Function* current_function_ = nullptr;
    /// The current block being emitted
    const core::ir::Block* current_block_ = nullptr;

    /// Emit the function
    /// @param func the function to emit
    void EmitFunction(const core::ir::Function* func) {
        TINT_SCOPED_ASSIGNMENT(current_function_, func);

        {
            auto out = Line();

            // TODO(dsinclair): Emit function stage if any
            // TODO(dsinclair): Handle return type attributes

            EmitType(out, func->ReturnType());
            out << " " << ir_.NameOf(func).Name() << "() {";

            // TODO(dsinclair): Emit Function parameters
        }
        {
            ScopedIndent si(current_buffer_);
            EmitBlock(func->Block());
        }

        Line() << "}";
    }

    /// Emit a block
    /// @param block the block to emit
    void EmitBlock(const core::ir::Block* block) {
        // TODO(dsinclair): Handle marking inline
        // MarkInlinable(block);

        EmitBlockInstructions(block);
    }

    /// Emit the instructions in a block
    /// @param block the block with the instructions to emit
    void EmitBlockInstructions(const core::ir::Block* block) {
        TINT_SCOPED_ASSIGNMENT(current_block_, block);

        for (auto* inst : *block) {
            Switch(
                inst,                                                      //
                [&](const core::ir::Return* r) { EmitReturn(r); },         //
                [&](const core::ir::Unreachable*) { EmitUnreachable(); },  //
                TINT_ICE_ON_NO_MATCH);
        }
    }

    /// Emit a type
    /// @param out the stream to emit too
    /// @param ty the type to emit
    void EmitType(StringStream& out, [[maybe_unused]] const core::type::Type* ty) { out << "void"; }

    /// Emit a return instruction
    /// @param r the return instruction
    void EmitReturn(const core::ir::Return* r) {
        // If this return has no arguments and the current block is for the function which is
        // being returned, skip the return.
        if (current_block_ == current_function_->Block() && r->Args().IsEmpty()) {
            return;
        }

        auto out = Line();
        out << "return";
        // TODO(dsinclair): Handle return args
        // if (!r->Args().IsEmpty()) {
        //     out << " " << Expr(r->Args().Front());
        // }
        out << ";";
    }

    /// Emit an unreachable instruction
    void EmitUnreachable() { Line() << "/* unreachable */"; }
};
}  // namespace

Result<std::string> Print(const core::ir::Module& module, const Version& version) {
    return Printer{module}.Generate(version);
}

}  // namespace tint::glsl::writer