/* Copyright 2025 The OpenXLA 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 XLA_CODEGEN_EMITTERS_CONCATENATE_KERNEL_EMITTER_H_
#define XLA_CODEGEN_EMITTERS_CONCATENATE_KERNEL_EMITTER_H_

#include <string>
#include <vector>

#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "mlir/Dialect/Func/IR/FuncOps.h"
#include "mlir/IR/MLIRContext.h"
#include "xla/codegen/emitters/computation_partitioner.h"
#include "xla/codegen/emitters/ir/xla_ops.h"
#include "xla/codegen/emitters/kernel_arguments.h"
#include "xla/codegen/hlo_fusion_spec.h"
#include "xla/codegen/kernel_emitter.h"
#include "xla/codegen/mlir_kernel_source.h"
#include "xla/hlo/analysis/indexing_map.h"
#include "xla/hlo/ir/hlo_instructions.h"
#include "xla/runtime/work_dimensions.h"
#include "xla/service/buffer_assignment.h"
#include "xla/shape.h"

namespace xla::emitters {

class ConcatenateFusionKernelEmitter final
    : public KernelEmitter<MlirKernelSource> {
 public:
  ConcatenateFusionKernelEmitter(
      mlir::MLIRContext& mlir_context, const HloFusionInstruction& fusion,
      const HloFusionSpec& fusion_spec,
      const BufferAssignment* buffer_assignment,
      KernelArguments::BufferAlignment buffer_alignment,
      WorkDimensions work_dimensions, absl::string_view entry_function_name,
      BackendKind backend_kind);

  absl::string_view name() const final {
    return "concatenate_fusion_kernel_emitter";
  }

  absl::StatusOr<KernelDefinition> EmitKernelDefinition() override;

  static IndexingMap ComputeWorkItemIdToOutputIndexing(
      const WorkDimensions& work_dimensions, const Shape& largest_shape,
      mlir::MLIRContext* ctx);

  // Get the shape used for indexing.
  // For concatenate, this is the largest shape.
  static const Shape& GetIndexingShape(const HloFusionSpec& fusion_spec);

  // Get the maximum valid unroll factor for the given fusion spec and maximum
  // unroll factor.
  // For concatenate, this is the greatest common divisor of the concatenate
  // dimension of all operands.
  static int GetValidUnrollFactor(const HloFusionSpec& fusion_spec,
                                  int max_unroll_factor);

 private:
  IndexingMap ComputeWorkItemIdToOutputIndexing(mlir::MLIRContext* ctx) const;

  absl::Status EmitEntryFunction(
      const emitters::PartitionedComputations& computations,
      const emitters::CallTargetProvider& call_targets,
      mlir::func::FuncOp entry_function,
      const HloFusionInstruction& fusion) const;

  std::vector<emitters::EpilogueSpecification> GetEpilogues(
      const HloFusionInstruction& fusion,
      mlir::MLIRContext* mlir_context) const;

 private:
  mlir::MLIRContext& mlir_context_;
  const HloFusionInstruction& fusion_;
  const HloFusionSpec& fusion_spec_;
  const BufferAssignment* buffer_assignment_;
  KernelArguments::BufferAlignment buffer_alignment_;
  WorkDimensions work_dimensions_;
  Shape largest_shape_;
  std::string entry_function_name_;
  BackendKind backend_kind_;
};

}  // namespace xla::emitters

#endif  // XLA_CODEGEN_EMITTERS_CONCATENATE_KERNEL_EMITTER_H_