/* SPDX-FileCopyrightText: 2023 Blender Foundation
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

#pragma once

/**
 * For evaluation, geometry node groups are converted to a lazy-function graph. The generated graph
 * is cached per node group, so it only has to be generated once after a change.
 *
 * Node groups are *not* inlined into the lazy-function graph. This could be added in the future as
 * it might improve performance in some cases, but generally does not seem necessary. Inlining node
 * groups also has disadvantages like making per-node-group caches less useful, resulting in more
 * overhead.
 *
 * Instead, group nodes are just like all other nodes in the lazy-function graph. What makes them
 * special is that they reference the lazy-function graph of the group they reference.
 *
 * During lazy-function graph generation, a mapping between the #bNodeTree and
 * #lazy_function::Graph is build that can be used when evaluating the graph (e.g. for logging).
 */

#include "FN_lazy_function_graph.hh"
#include "FN_lazy_function_graph_executor.hh"

#include "NOD_geometry_nodes_log.hh"
#include "NOD_multi_function.hh"

#include "BLI_compute_context.hh"

#include "BKE_node_tree_zones.hh"
#include "BKE_simulation_state.hh"

struct Object;
struct Depsgraph;

namespace blender::nodes {

using lf::LazyFunction;
using mf::MultiFunction;

/**
 * Data that is passed into geometry nodes evaluation from the modifier.
 */
struct GeoNodesModifierData {
  /** Object that is currently evaluated. */
  const Object *self_object = nullptr;
  /** Depsgraph that is evaluating the modifier. */
  Depsgraph *depsgraph = nullptr;
  /** Optional logger. */
  geo_eval_log::GeoModifierLog *eval_log = nullptr;

  /** Read-only simulation states around the current frame. */
  const bke::sim::ModifierSimulationState *current_simulation_state = nullptr;
  const bke::sim::ModifierSimulationState *prev_simulation_state = nullptr;
  const bke::sim::ModifierSimulationState *next_simulation_state = nullptr;
  float simulation_state_mix_factor = 0.0f;
  /** Used when the evaluation should create a new simulation state. */
  bke::sim::ModifierSimulationState *current_simulation_state_for_write = nullptr;
  float simulation_time_delta = 0.0f;

  /**
   * The same as #prev_simulation_state, but the cached values can be moved from,
   * to keep data managed by implicit sharing mutable.
   */
  bke::sim::ModifierSimulationState *prev_simulation_state_mutable = nullptr;

  /**
   * Some nodes should be executed even when their output is not used (e.g. active viewer nodes and
   * the node groups they are contained in).
   */
  const MultiValueMap<ComputeContextHash, const lf::FunctionNode *> *side_effect_nodes = nullptr;
  /**
   * Controls in which compute contexts we want to log socket values. Logging them in all contexts
   * can result in slowdowns. In the majority of cases, the logged socket values are freed without
   * being looked at anyway.
   *
   * If this is null, all socket values will be logged.
   */
  const Set<ComputeContextHash> *socket_log_contexts = nullptr;
};

struct GeoNodesOperatorData {
  /** The object currently effected by the operator. */
  const Object *self_object = nullptr;
  /** Current evaluated depsgraph. */
  Depsgraph *depsgraph = nullptr;
};

/**
 * Custom user data that is passed to every geometry nodes related lazy-function evaluation.
 */
struct GeoNodesLFUserData : public lf::UserData {
  /**
   * Data from the modifier that is being evaluated.
   */
  GeoNodesModifierData *modifier_data = nullptr;
  /**
   * Data from execution as operator in 3D viewport.
   */
  GeoNodesOperatorData *operator_data = nullptr;
  /**
   * Current compute context. This is different depending in the (nested) node group that is being
   * evaluated.
   */
  const ComputeContext *compute_context = nullptr;
  /**
   * Log socket values in the current compute context. Child contexts might use logging again.
   */
  bool log_socket_values = true;
  /**
   * Top-level node tree of the current evaluation.
   */
  const bNodeTree *root_ntree = nullptr;

  destruct_ptr<lf::LocalUserData> get_local(LinearAllocator<> &allocator) override;
};

struct GeoNodesLFLocalUserData : public lf::LocalUserData {
 public:
  /**
   * Thread-local logger for the current node tree in the current compute context.
   */
  geo_eval_log::GeoTreeLogger *tree_logger = nullptr;

  GeoNodesLFLocalUserData(GeoNodesLFUserData &user_data);
};

/**
 * In the general case, this is #DynamicSocket. That means that to determine if a node group will
 * use a particular input, it has to be partially executed.
 *
 * In other cases, it's not necessary to look into the node group to determine if an input is
 * necessary.
 */
enum class InputUsageHintType {
  /** The input socket is never used. */
  Never,
  /** The input socket is used when a subset of the outputs is used. */
  DependsOnOutput,
  /** Can't determine statically if the input is used, check the corresponding output socket. */
  DynamicSocket,
};

struct InputUsageHint {
  InputUsageHintType type = InputUsageHintType::DependsOnOutput;
  /** Used in depends-on-output mode. */
  Vector<int> output_dependencies;
};

/**
 * Contains the mapping between the #bNodeTree and the corresponding lazy-function graph.
 * This is *not* a one-to-one mapping.
 */
struct GeometryNodeLazyFunctionGraphMapping {
  /**
   * Contains mapping of sockets for special nodes like group input and group output.
   */
  Map<const bNodeSocket *, lf::Socket *> dummy_socket_map;
  /**
   * The inputs sockets in the graph. Multiple group input nodes are combined into one in the
   * lazy-function graph.
   */
  Vector<const lf::OutputSocket *> group_input_sockets;
  /**
   * Dummy output sockets that correspond to the active group output node. If there is no such
   * node, defaulted fallback outputs are created.
   */
  Vector<const lf::InputSocket *> standard_group_output_sockets;
  /**
   * Dummy boolean sockets that have to be passed in from the outside and indicate whether a
   * specific output will be used.
   */
  Vector<const lf::OutputSocket *> group_output_used_sockets;
  /**
   * Dummy boolean sockets that can be used as group output that indicate whether a specific input
   * will be used (this may depend on the used outputs as well as other inputs).
   */
  Vector<const lf::InputSocket *> group_input_usage_sockets;
  /**
   * This is an optimization to avoid partially evaluating a node group just to figure out which
   * inputs are needed.
   */
  Vector<InputUsageHint> group_input_usage_hints;
  /**
   * If the node group propagates attributes from an input geometry to the output, it has to know
   * which attributes should be propagated and which can be removed (for optimization purposes).
   */
  Map<int, const lf::OutputSocket *> attribute_set_by_geometry_output;
  /**
   * A mapping used for logging intermediate values.
   */
  MultiValueMap<const lf::Socket *, const bNodeSocket *> bsockets_by_lf_socket_map;
  /**
   * Mappings for some special node types. Generally, this mapping does not exist for all node
   * types, so better have more specialized mappings for now.
   */
  Map<const bNode *, const lf::FunctionNode *> group_node_map;
  Map<const bNode *, const lf::FunctionNode *> viewer_node_map;
  Map<const bke::bNodeTreeZone *, const lf::FunctionNode *> zone_node_map;

  /* Indexed by #bNodeSocket::index_in_all_outputs. */
  Array<int> lf_input_index_for_output_bsocket_usage;
  /* Indexed by #bNodeSocket::index_in_all_outputs. */
  Array<int> lf_input_index_for_attribute_propagation_to_output;
  /* Indexed by #bNodeSocket::index_in_tree. */
  Array<int> lf_index_by_bsocket;
};

/**
 * Data that is cached for every #bNodeTree.
 */
struct GeometryNodesLazyFunctionGraphInfo {
  /**
   * Contains resources that need to be freed when the graph is not needed anymore.
   */
  ResourceScope scope;
  /**
   * The actual lazy-function graph.
   */
  lf::Graph graph;
  /**
   * Mappings between the lazy-function graph and the #bNodeTree.
   */
  GeometryNodeLazyFunctionGraphMapping mapping;
  /**
   * Approximate number of nodes in the graph if all sub-graphs were inlined.
   * This can be used as a simple heuristic for the complexity of the node group.
   */
  int num_inline_nodes_approximate = 0;
};

/**
 * Logs intermediate values from the lazy-function graph evaluation into #GeoModifierLog based on
 * the mapping between the lazy-function graph and the corresponding #bNodeTree.
 */
class GeometryNodesLazyFunctionLogger : public fn::lazy_function::GraphExecutor::Logger {
 private:
  const GeometryNodesLazyFunctionGraphInfo &lf_graph_info_;

 public:
  GeometryNodesLazyFunctionLogger(const GeometryNodesLazyFunctionGraphInfo &lf_graph_info);
  void log_socket_value(const fn::lazy_function::Socket &lf_socket,
                        GPointer value,
                        const fn::lazy_function::Context &context) const override;
  void dump_when_outputs_are_missing(const lf::FunctionNode &node,
                                     Span<const lf::OutputSocket *> missing_sockets,
                                     const lf::Context &context) const override;
  void dump_when_input_is_set_twice(const lf::InputSocket &target_socket,
                                    const lf::OutputSocket &from_socket,
                                    const lf::Context &context) const override;
  void log_before_node_execute(const lf::FunctionNode &node,
                               const lf::Params &params,
                               const lf::Context &context) const override;
};

std::unique_ptr<LazyFunction> get_simulation_output_lazy_function(
    const bNode &node, GeometryNodesLazyFunctionGraphInfo &own_lf_graph_info);
std::unique_ptr<LazyFunction> get_simulation_input_lazy_function(
    const bNodeTree &node_tree,
    const bNode &node,
    GeometryNodesLazyFunctionGraphInfo &own_lf_graph_info);
std::unique_ptr<LazyFunction> get_switch_node_lazy_function(const bNode &node);

std::optional<bke::sim::SimulationZoneID> get_simulation_zone_id(
    const GeoNodesLFUserData &user_data, const int output_node_id);

/**
 * An anonymous attribute created by a node.
 */
class NodeAnonymousAttributeID : public bke::AnonymousAttributeID {
  std::string long_name_;
  std::string socket_name_;

 public:
  NodeAnonymousAttributeID(const Object &object,
                           const ComputeContext &compute_context,
                           const bNode &bnode,
                           const StringRef identifier,
                           const StringRef name);

  std::string user_name() const override;
};

/**
 * Tells the lazy-function graph evaluator which nodes have side effects based on the current
 * context. For example, the same viewer node can have side effects in one context, but not in
 * another (depending on e.g. which tree path is currently viewed in the node editor).
 */
class GeometryNodesLazyFunctionSideEffectProvider
    : public fn::lazy_function::GraphExecutor::SideEffectProvider {
 public:
  Vector<const lf::FunctionNode *> get_nodes_with_side_effects(
      const lf::Context &context) const override;
};

/**
 * Main function that converts a #bNodeTree into a lazy-function graph. If the graph has been
 * generated already, nothing is done. Under some circumstances a valid graph cannot be created. In
 * those cases null is returned.
 */
const GeometryNodesLazyFunctionGraphInfo *ensure_geometry_nodes_lazy_function_graph(
    const bNodeTree &btree);

}  // namespace blender::nodes
