// Copyright 2020 The Tint Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef SRC_TINT_RESOLVER_RESOLVER_H_
#define SRC_TINT_RESOLVER_RESOLVER_H_

#include <memory>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#include "src/tint/builtin_table.h"
#include "src/tint/program_builder.h"
#include "src/tint/resolver/dependency_graph.h"
#include "src/tint/resolver/sem_helper.h"
#include "src/tint/resolver/validator.h"
#include "src/tint/scope_stack.h"
#include "src/tint/sem/binding_point.h"
#include "src/tint/sem/block_statement.h"
#include "src/tint/sem/constant.h"
#include "src/tint/sem/function.h"
#include "src/tint/sem/struct.h"
#include "src/tint/utils/unique_vector.h"

// Forward declarations
namespace tint::ast {
class IndexAccessorExpression;
class BinaryExpression;
class BitcastExpression;
class CallExpression;
class CallStatement;
class CaseStatement;
class ForLoopStatement;
class Function;
class IdentifierExpression;
class LoopStatement;
class MemberAccessorExpression;
class ReturnStatement;
class SwitchStatement;
class UnaryOpExpression;
class Variable;
}  // namespace tint::ast
namespace tint::sem {
class Array;
class Atomic;
class BlockStatement;
class Builtin;
class CaseStatement;
class ElseStatement;
class ForLoopStatement;
class IfStatement;
class LoopStatement;
class Statement;
class SwitchStatement;
class TypeConstructor;
}  // namespace tint::sem

namespace tint::resolver {

/// Resolves types for all items in the given tint program
class Resolver {
 public:
  /// Constructor
  /// @param builder the program builder
  explicit Resolver(ProgramBuilder* builder);

  /// Destructor
  ~Resolver();

  /// @returns error messages from the resolver
  std::string error() const { return diagnostics_.str(); }

  /// @returns true if the resolver was successful
  bool Resolve();

  /// @param type the given type
  /// @returns true if the given type is a plain type
  bool IsPlain(const sem::Type* type) const { return validator_.IsPlain(type); }

  /// @param type the given type
  /// @returns true if the given type is a fixed-footprint type
  bool IsFixedFootprint(const sem::Type* type) const {
    return validator_.IsFixedFootprint(type);
  }

  /// @param type the given type
  /// @returns true if the given type is storable
  bool IsStorable(const sem::Type* type) const {
    return validator_.IsStorable(type);
  }

  /// @param type the given type
  /// @returns true if the given type is host-shareable
  bool IsHostShareable(const sem::Type* type) const {
    return validator_.IsHostShareable(type);
  }

  /// @returns the validator for testing
  const Validator* GetValidatorForTesting() const { return &validator_; }

 private:
  /// Describes the context in which a variable is declared
  enum class VariableKind { kParameter, kLocal, kGlobal };

  Validator::ValidTypeStorageLayouts valid_type_storage_layouts_;

  /// Structure holding semantic information about a block (i.e. scope), such as
  /// parent block and variables declared in the block.
  /// Used to validate variable scoping rules.
  struct BlockInfo {
    enum class Type { kGeneric, kLoop, kLoopContinuing, kSwitchCase };

    BlockInfo(const ast::BlockStatement* block, Type type, BlockInfo* parent);
    ~BlockInfo();

    template <typename Pred>
    BlockInfo* FindFirstParent(Pred&& pred) {
      BlockInfo* curr = this;
      while (curr && !pred(curr)) {
        curr = curr->parent;
      }
      return curr;
    }

    BlockInfo* FindFirstParent(BlockInfo::Type ty) {
      return FindFirstParent(
          [ty](auto* block_info) { return block_info->type == ty; });
    }

    ast::BlockStatement const* const block;
    const Type type;
    BlockInfo* const parent;
    std::vector<const ast::Variable*> decls;

    // first_continue is set to the index of the first variable in decls
    // declared after the first continue statement in a loop block, if any.
    constexpr static size_t kNoContinue = size_t(~0);
    size_t first_continue = kNoContinue;
  };

  // Structure holding information for a TypeDecl
  struct TypeDeclInfo {
    ast::TypeDecl const* const ast;
    sem::Type* const sem;
  };

  /// Resolves the program, without creating final the semantic nodes.
  /// @returns true on success, false on error
  bool ResolveInternal();

  /// Creates the nodes and adds them to the sem::Info mappings of the
  /// ProgramBuilder.
  void CreateSemanticNodes() const;

  /// Retrieves information for the requested import.
  /// @param src the source of the import
  /// @param path the import path
  /// @param name the method name to get information on
  /// @param params the parameters to the method call
  /// @param id out parameter for the external call ID. Must not be a nullptr.
  /// @returns the return type of `name` in `path` or nullptr on error.
  sem::Type* GetImportData(const Source& src,
                           const std::string& path,
                           const std::string& name,
                           const ast::ExpressionList& params,
                           uint32_t* id);

  //////////////////////////////////////////////////////////////////////////////
  // AST and Type traversal methods
  //////////////////////////////////////////////////////////////////////////////

  // Expression resolving methods
  // Returns the semantic node pointer on success, nullptr on failure.
  sem::Expression* IndexAccessor(const ast::IndexAccessorExpression*);
  sem::Expression* Binary(const ast::BinaryExpression*);
  sem::Expression* Bitcast(const ast::BitcastExpression*);
  sem::Call* Call(const ast::CallExpression*);
  sem::Expression* Expression(const ast::Expression*);
  sem::Function* Function(const ast::Function*);
  sem::Call* FunctionCall(const ast::CallExpression*,
                          sem::Function* target,
                          const std::vector<const sem::Expression*> args,
                          sem::Behaviors arg_behaviors);
  sem::Expression* Identifier(const ast::IdentifierExpression*);
  sem::Call* BuiltinCall(const ast::CallExpression*,
                         sem::BuiltinType,
                         const std::vector<const sem::Expression*> args,
                         const std::vector<const sem::Type*> arg_tys);
  sem::Expression* Literal(const ast::LiteralExpression*);
  sem::Expression* MemberAccessor(const ast::MemberAccessorExpression*);
  sem::Call* TypeConversion(const ast::CallExpression* expr,
                            const sem::Type* ty,
                            const sem::Expression* arg,
                            const sem::Type* arg_ty);
  sem::Call* TypeConstructor(const ast::CallExpression* expr,
                             const sem::Type* ty,
                             const std::vector<const sem::Expression*> args,
                             const std::vector<const sem::Type*> arg_tys);
  sem::Expression* UnaryOp(const ast::UnaryOpExpression*);

  // Statement resolving methods
  // Each return true on success, false on failure.
  sem::Statement* AssignmentStatement(const ast::AssignmentStatement*);
  sem::BlockStatement* BlockStatement(const ast::BlockStatement*);
  sem::Statement* BreakStatement(const ast::BreakStatement*);
  sem::Statement* CallStatement(const ast::CallStatement*);
  sem::CaseStatement* CaseStatement(const ast::CaseStatement*);
  sem::Statement* CompoundAssignmentStatement(
      const ast::CompoundAssignmentStatement*);
  sem::Statement* ContinueStatement(const ast::ContinueStatement*);
  sem::Statement* DiscardStatement(const ast::DiscardStatement*);
  sem::ElseStatement* ElseStatement(const ast::ElseStatement*);
  sem::Statement* FallthroughStatement(const ast::FallthroughStatement*);
  sem::ForLoopStatement* ForLoopStatement(const ast::ForLoopStatement*);
  sem::GlobalVariable* GlobalVariable(const ast::Variable*);
  sem::Statement* Parameter(const ast::Variable*);
  sem::IfStatement* IfStatement(const ast::IfStatement*);
  sem::Statement* IncrementDecrementStatement(
      const ast::IncrementDecrementStatement*);
  sem::LoopStatement* LoopStatement(const ast::LoopStatement*);
  sem::Statement* ReturnStatement(const ast::ReturnStatement*);
  sem::Statement* Statement(const ast::Statement*);
  sem::SwitchStatement* SwitchStatement(const ast::SwitchStatement* s);
  sem::Statement* VariableDeclStatement(const ast::VariableDeclStatement*);
  bool Statements(const ast::StatementList&);

  // Resolve the result type of a binary operator.
  // Returns nullptr if the types are not valid for this operator.
  const sem::Type* BinaryOpType(const sem::Type* lhs_ty,
                                const sem::Type* rhs_ty,
                                ast::BinaryOp op);

  /// Resolves the WorkgroupSize for the given function, assigning it to
  /// current_function_
  bool WorkgroupSize(const ast::Function*);

  /// @returns the sem::Type for the ast::Type `ty`, building it if it
  /// hasn't been constructed already. If an error is raised, nullptr is
  /// returned.
  /// @param ty the ast::Type
  sem::Type* Type(const ast::Type* ty);

  /// @param named_type the named type to resolve
  /// @returns the resolved semantic type
  sem::Type* TypeDecl(const ast::TypeDecl* named_type);

  /// Builds and returns the semantic information for the array `arr`.
  /// This method does not mark the ast::Array node, nor attach the generated
  /// semantic information to the AST node.
  /// @returns the semantic Array information, or nullptr if an error is
  /// raised.
  /// @param arr the Array to get semantic information for
  sem::Array* Array(const ast::Array* arr);

  /// Builds and returns the semantic information for the alias `alias`.
  /// This method does not mark the ast::Alias node, nor attach the generated
  /// semantic information to the AST node.
  /// @returns the aliased type, or nullptr if an error is raised.
  sem::Type* Alias(const ast::Alias* alias);

  /// Builds and returns the semantic information for the structure `str`.
  /// This method does not mark the ast::Struct node, nor attach the generated
  /// semantic information to the AST node.
  /// @returns the semantic Struct information, or nullptr if an error is
  /// raised.
  sem::Struct* Structure(const ast::Struct* str);

  /// @returns the semantic info for the variable `var`. If an error is
  /// raised, nullptr is returned.
  /// @note this method does not resolve the attributes as these are
  /// context-dependent (global, local, parameter)
  /// @param var the variable to create or return the `VariableInfo` for
  /// @param kind what kind of variable we are declaring
  /// @param index the index of the parameter, if this variable is a parameter
  sem::Variable* Variable(const ast::Variable* var,
                          VariableKind kind,
                          uint32_t index = 0);

  /// Records the storage class usage for the given type, and any transient
  /// dependencies of the type. Validates that the type can be used for the
  /// given storage class, erroring if it cannot.
  /// @param sc the storage class to apply to the type and transitent types
  /// @param ty the type to apply the storage class on
  /// @param usage the Source of the root variable declaration that uses the
  /// given type and storage class. Used for generating sensible error
  /// messages.
  /// @returns true on success, false on error
  bool ApplyStorageClassUsageToType(ast::StorageClass sc,
                                    sem::Type* ty,
                                    const Source& usage);

  /// @param storage_class the storage class
  /// @returns the default access control for the given storage class
  ast::Access DefaultAccessForStorageClass(ast::StorageClass storage_class);

  /// Allocate constant IDs for pipeline-overridable constants.
  void AllocateOverridableConstantIds();

  /// Set the shadowing information on variable declarations.
  /// @note this method must only be called after all semantic nodes are built.
  void SetShadows();
  /// StatementScope() does the following:
  /// * Creates the AST -> SEM mapping.
  /// * Assigns `sem` to #current_statement_
  /// * Assigns `sem` to #current_compound_statement_ if `sem` derives from
  ///   sem::CompoundStatement.
  /// * Assigns `sem` to #current_block_ if `sem` derives from
  ///   sem::BlockStatement.
  /// * Then calls `callback`.
  /// * Before returning #current_statement_, #current_compound_statement_, and
  ///   #current_block_ are restored to their original values.
  /// @returns `sem` if `callback` returns true, otherwise `nullptr`.
  template <typename SEM, typename F>
  SEM* StatementScope(const ast::Statement* ast, SEM* sem, F&& callback);

  /// Mark records that the given AST node has been visited, and asserts that
  /// the given node has not already been seen. Diamonds in the AST are
  /// illegal.
  /// @param node the AST node.
  /// @returns true on success, false on error
  bool Mark(const ast::Node* node);

  /// Adds the given error message to the diagnostics
  void AddError(const std::string& msg, const Source& source) const;

  /// Adds the given warning message to the diagnostics
  void AddWarning(const std::string& msg, const Source& source) const;

  /// Adds the given note message to the diagnostics
  void AddNote(const std::string& msg, const Source& source) const;

  //////////////////////////////////////////////////////////////////////////////
  /// Constant value evaluation methods
  //////////////////////////////////////////////////////////////////////////////
  /// Cast `Value` to `target_type`
  /// @return the casted value
  sem::Constant ConstantCast(const sem::Constant& value,
                             const sem::Type* target_elem_type);

  sem::Constant EvaluateConstantValue(const ast::Expression* expr,
                                      const sem::Type* type);
  sem::Constant EvaluateConstantValue(const ast::LiteralExpression* literal,
                                      const sem::Type* type);
  sem::Constant EvaluateConstantValue(const ast::CallExpression* call,
                                      const sem::Type* type);

  /// @returns true if the symbol is the name of a builtin function.
  bool IsBuiltin(Symbol) const;

  /// @returns true if `expr` is the current CallStatement's CallExpression
  bool IsCallStatement(const ast::Expression* expr) const;

  struct TypeConversionSig {
    const sem::Type* target;
    const sem::Type* source;

    bool operator==(const TypeConversionSig&) const;

    /// Hasher provides a hash function for the TypeConversionSig
    struct Hasher {
      /// @param sig the TypeConversionSig to create a hash for
      /// @return the hash value
      std::size_t operator()(const TypeConversionSig& sig) const;
    };
  };

  struct TypeConstructorSig {
    const sem::Type* type;
    const std::vector<const sem::Type*> parameters;

    TypeConstructorSig(const sem::Type* ty,
                       const std::vector<const sem::Type*> params);
    TypeConstructorSig(const TypeConstructorSig&);
    ~TypeConstructorSig();
    bool operator==(const TypeConstructorSig&) const;

    /// Hasher provides a hash function for the TypeConstructorSig
    struct Hasher {
      /// @param sig the TypeConstructorSig to create a hash for
      /// @return the hash value
      std::size_t operator()(const TypeConstructorSig& sig) const;
    };
  };

  ProgramBuilder* const builder_;
  diag::List& diagnostics_;
  std::unique_ptr<BuiltinTable> const builtin_table_;
  DependencyGraph dependencies_;
  SemHelper sem_;
  Validator validator_;
  std::vector<sem::Function*> entry_points_;
  std::unordered_map<const sem::Type*, const Source&> atomic_composite_info_;
  std::unordered_set<const ast::Node*> marked_;
  std::unordered_map<uint32_t, const sem::Variable*> constant_ids_;
  std::unordered_map<TypeConversionSig,
                     sem::CallTarget*,
                     TypeConversionSig::Hasher>
      type_conversions_;
  std::unordered_map<TypeConstructorSig,
                     sem::CallTarget*,
                     TypeConstructorSig::Hasher>
      type_ctors_;

  sem::Function* current_function_ = nullptr;
  sem::Statement* current_statement_ = nullptr;
  sem::CompoundStatement* current_compound_statement_ = nullptr;
  sem::BlockStatement* current_block_ = nullptr;
};

}  // namespace tint::resolver

#endif  // SRC_TINT_RESOLVER_RESOLVER_H_