// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef ZIRCON_SYSTEM_HOST_FIDL_INCLUDE_FIDL_CODED_AST_H_
#define ZIRCON_SYSTEM_HOST_FIDL_INCLUDE_FIDL_CODED_AST_H_

#include <stdint.h>

#include <memory>
#include <string>
#include <vector>

#include "types.h"

// The types in this file define structures that much more closely map
// the coding tables (i.e., fidl_type_t) for (de)serialization,
// defined at ulib/fidl/include/coding.h and so on.

// In particular, compared to the flat_ast version:
// - All files in the library are resolved together
// - Names have been unnested and fully qualified
// - All data structure sizes and layouts have been computed

namespace fidl {
namespace coded {

enum struct CodingContext {
    // The coding table of this type will be used to represent data within
    // an envelope. This will affect the 'coding needed'.
    kInsideEnvelope,

    // The coding table of this type will be used to represent data outside
    // of an envelope, and default 'coding needed' is appropriate here.
    kOutsideEnvelope,
};

enum struct CodingNeeded {
    // There is interesting coding information about the location of
    // pointers, allocations, or handles for this type.
    kAlways,

    // The type contains no pointers or handles. However, we should generate
    // corresponding coding information when it is wrapped in an envelope,
    // to support encoding/decoding of xunions and tables.
    kEnvelopeOnly,
};

namespace {

CodingNeeded WhichCodingNeeded(CodingContext context, CodingNeeded coding_needed) {
    switch (context) {
    case CodingContext::kInsideEnvelope:
        return CodingNeeded::kAlways;
    case CodingContext::kOutsideEnvelope:
        return coding_needed;
    }
}

} // namespace

struct Type;

struct StructField {
    StructField(const Type* type, uint32_t offset)
        : type(type), offset(offset) {}

    const Type* type;
    const uint32_t offset;
};

// This carries the same information as the XUnionField struct below and
// arguably violates DRY, but it's useful to make it a different type to
// distinguish its use-case in code, and also to make it easier to change later
// if necessary. (Gotta do something at least three times before we abstract it
// out, right?)
struct TableField {
    TableField(const Type* type, uint32_t ordinal)
        : type(type), ordinal(ordinal) {}

    const Type* type;
    const uint32_t ordinal;
};

// This carries the same information as the TableField struct above and arguably
// violates DRY, but it's useful to make it a different type to distinguish its
// use-case in code, and also to make it easier to change later if necessary.
// (Gotta do something at least three times before we abstract it out, right?)
struct XUnionField {
    XUnionField(const Type* type, uint32_t ordinal)
        : type(type), ordinal(ordinal) {}

    const Type* type;
    const uint32_t ordinal;
};

struct Type {
    virtual ~Type() = default;

    enum struct Kind {
        kPrimitive,
        kHandle,
        kInterfaceHandle,
        kRequestHandle,
        kStruct,
        kTable,
        kUnion,
        kXUnion,
        kPointer,
        kMessage,
        kInterface,
        kArray,
        kString,
        kVector,
    };

    Type(Kind kind, std::string coded_name, uint32_t size, CodingNeeded coding_needed)
        : kind(kind), coded_name(std::move(coded_name)), size(size), coding_needed(coding_needed) {}

    const Kind kind;
    const std::string coded_name;
    uint32_t size;
    const CodingNeeded coding_needed;
};

struct PrimitiveType : public Type {
    PrimitiveType(std::string name, types::PrimitiveSubtype subtype, uint32_t size,
                  CodingContext context)
        : Type(Kind::kPrimitive, std::move(name), size,
               WhichCodingNeeded(context, CodingNeeded::kEnvelopeOnly)),
          subtype(subtype) {}

    const types::PrimitiveSubtype subtype;
};

struct HandleType : public Type {
    HandleType(std::string name, types::HandleSubtype subtype, types::Nullability nullability)
        : Type(Kind::kHandle, std::move(name), 4u, CodingNeeded::kAlways), subtype(subtype),
          nullability(nullability) {}

    const types::HandleSubtype subtype;
    const types::Nullability nullability;
};

struct InterfaceHandleType : public Type {
    InterfaceHandleType(std::string name, types::Nullability nullability)
        : Type(Kind::kInterfaceHandle, std::move(name), 4u, CodingNeeded::kAlways),
          nullability(nullability) {}

    const types::Nullability nullability;
};

struct RequestHandleType : public Type {
    RequestHandleType(std::string name, types::Nullability nullability)
        : Type(Kind::kRequestHandle, std::move(name), 4u, CodingNeeded::kAlways),
          nullability(nullability) {}

    const types::Nullability nullability;
};

struct PointerType : public Type {
    PointerType(std::string name, const Type* type)
        : Type(Kind::kPointer, std::move(name), 8u, CodingNeeded::kAlways),
          element_type(type) {}

    const Type* element_type;
};

struct StructType : public Type {
    StructType(std::string name, std::vector<StructField> fields, uint32_t size, std::string qname)
        : Type(Kind::kStruct, std::move(name), size, CodingNeeded::kAlways),
          fields(std::move(fields)), qname(std::move(qname)) {}

    std::vector<StructField> fields;
    std::string qname;
    PointerType* maybe_reference_type = nullptr;
};

struct UnionType : public Type {
    UnionType(std::string name, std::vector<const Type*> types, uint32_t data_offset, uint32_t size,
              std::string qname)
        : Type(Kind::kUnion, std::move(name), size, CodingNeeded::kAlways), types(std::move(types)),
          data_offset(data_offset), qname(std::move(qname)) {
    }

    std::vector<const Type*> types;
    const uint32_t data_offset;
    std::string qname;
    PointerType* maybe_reference_type = nullptr;
};

struct TableType : public Type {
    TableType(std::string name, std::vector<TableField> fields, uint32_t size, std::string qname)
        : Type(Kind::kTable, std::move(name), size, CodingNeeded::kAlways),
          fields(std::move(fields)), qname(std::move(qname)) {}

    std::vector<TableField> fields;
    std::string qname;
};

struct XUnionType : public Type {
    XUnionType(std::string name, std::vector<XUnionField> fields, std::string qname,
               types::Nullability nullability)
        : Type(Kind::kXUnion, std::move(name), 24u, CodingNeeded::kAlways),
          fields(std::move(fields)), qname(std::move(qname)), nullability(nullability) {}

    std::vector<XUnionField> fields;
    const std::string qname;
    types::Nullability nullability;
    XUnionType* maybe_reference_type = nullptr;
};

struct MessageType : public Type {
    MessageType(std::string name, std::vector<StructField> fields, uint32_t size, std::string qname)
        : Type(Kind::kMessage, std::move(name), size, CodingNeeded::kAlways),
          fields(std::move(fields)), qname(std::move(qname)) {}

    std::vector<StructField> fields;
    std::string qname;
};

struct InterfaceType : public Type {
    explicit InterfaceType(std::vector<std::unique_ptr<MessageType>> messages)
        // N.B. InterfaceTypes are never used in the eventual coding table generation.
        : Type(Kind::kInterface, "", 0, CodingNeeded::kEnvelopeOnly),
          messages(std::move(messages)) {}

    std::vector<std::unique_ptr<MessageType>> messages;
};

struct ArrayType : public Type {
    ArrayType(std::string name, const Type* element_type, uint32_t array_size,
              uint32_t element_size, CodingContext context)
        : Type(Kind::kArray, std::move(name), array_size,
               WhichCodingNeeded(context, element_type->coding_needed)),
          element_type(element_type), element_size(element_size) {}

    const Type* const element_type;
    const uint32_t element_size;
};

struct StringType : public Type {
    StringType(std::string name, uint32_t max_size, types::Nullability nullability)
        : Type(Kind::kString, std::move(name), 16u, CodingNeeded::kAlways), max_size(max_size),
          nullability(nullability) {}

    const uint32_t max_size;
    const types::Nullability nullability;
};

struct VectorType : public Type {
    VectorType(std::string name, const Type* element_type, uint32_t max_count,
               uint32_t element_size, types::Nullability nullability)
        : Type(Kind::kVector, std::move(name), 16u, CodingNeeded::kAlways),
          element_type(element_type), max_count(max_count), element_size(element_size),
          nullability(nullability) {}

    const Type* const element_type;
    const uint32_t max_count;
    const uint32_t element_size;
    const types::Nullability nullability;
};

} // namespace coded
} // namespace fidl

#endif // ZIRCON_SYSTEM_HOST_FIDL_INCLUDE_FIDL_CODED_AST_H_