use std::borrow::Cow;

use std::collections::{HashMap, HashSet};
use std::ops::Deref;

use std::hash::Hash;

use crate::document::NodeId;
use crate::document::{value, InlineRust};
use dyn_any::DynAny;
use graphene_core::*;
#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};
use std::pin::Pin;

pub type DynFuture<'n, T> = Pin<Box<dyn core::future::Future<Output = T> + 'n>>;
pub type LocalFuture<'n, T> = Pin<Box<dyn core::future::Future<Output = T> + 'n>>;
pub type Any<'n> = Box<dyn DynAny<'n> + 'n>;
pub type FutureAny<'n> = DynFuture<'n, Any<'n>>;
// TODO: is this safe? This is assumed to be send+sync.
pub type TypeErasedNode<'n> = dyn for<'i> NodeIO<'i, Any<'i>, Output = FutureAny<'i>> + 'n;
pub type TypeErasedPinnedRef<'n> = Pin<&'n TypeErasedNode<'n>>;
pub type TypeErasedRef<'n> = &'n TypeErasedNode<'n>;
pub type TypeErasedBox<'n> = Box<TypeErasedNode<'n>>;
pub type TypeErasedPinned<'n> = Pin<Box<TypeErasedNode<'n>>>;

pub type SharedNodeContainer = std::rc::Rc<NodeContainer>;

pub type NodeConstructor = for<'a> fn(Vec<SharedNodeContainer>) -> DynFuture<'static, TypeErasedBox<'static>>;

#[derive(Clone)]
pub struct NodeContainer {
	#[cfg(feature = "dealloc_nodes")]
	pub node: *mut TypeErasedNode<'static>,
	#[cfg(not(feature = "dealloc_nodes"))]
	pub node: TypeErasedRef<'static>,
}

impl Deref for NodeContainer {
	type Target = TypeErasedNode<'static>;

	#[cfg(feature = "dealloc_nodes")]
	fn deref(&self) -> &Self::Target {
		unsafe { &*(self.node as *const TypeErasedNode) }
		#[cfg(not(feature = "dealloc_nodes"))]
		self.node
	}
	#[cfg(not(feature = "dealloc_nodes"))]
	fn deref(&self) -> &Self::Target {
		self.node
	}
}

#[cfg(feature = "dealloc_nodes")]
impl Drop for NodeContainer {
	fn drop(&mut self) {
		unsafe { self.dealloc_unchecked() }
	}
}

impl core::fmt::Debug for NodeContainer {
	fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> std::fmt::Result {
		f.debug_struct("NodeContainer").finish()
	}
}

impl NodeContainer {
	pub fn new(node: TypeErasedBox<'static>) -> SharedNodeContainer {
		let node = Box::leak(node);
		Self { node }.into()
	}

	#[cfg(feature = "dealloc_nodes")]
	unsafe fn dealloc_unchecked(&mut self) {
		std::mem::drop(Box::from_raw(self.node));
	}
}

#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Debug, Default, PartialEq, Clone, Hash, Eq)]
/// A list of [`ProtoNode`]s, which is an intermediate step between the [`crate::document::NodeNetwork`] and the `BorrowTree` containing a single flattened network.
pub struct ProtoNetwork {
	// TODO: remove this since it seems to be unused?
	// Should a proto Network even allow inputs? Don't think so
	pub inputs: Vec<NodeId>,
	/// The node ID that provides the output. This node is then responsible for calling the rest of the graph.
	pub output: NodeId,
	/// A list of nodes stored in a Vec to allow for sorting.
	pub nodes: Vec<(NodeId, ProtoNode)>,
}

impl core::fmt::Display for ProtoNetwork {
	fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
		f.write_str("Proto Network with nodes: ")?;
		fn write_node(f: &mut core::fmt::Formatter<'_>, network: &ProtoNetwork, id: NodeId, indent: usize) -> core::fmt::Result {
			f.write_str(&"\t".repeat(indent))?;
			let Some((_, node)) = network.nodes.iter().find(|(node_id, _)| *node_id == id) else {
				return f.write_str("{{Unknown Node}}");
			};
			f.write_str("Node: ")?;
			f.write_str(&node.identifier.name)?;

			f.write_str("\n")?;
			f.write_str(&"\t".repeat(indent))?;
			f.write_str("{\n")?;

			f.write_str(&"\t".repeat(indent + 1))?;
			f.write_str("Primary input: ")?;
			match &node.input {
				ProtoNodeInput::None => f.write_str("None")?,
				ProtoNodeInput::ManualComposition(ty) => f.write_fmt(format_args!("Manual Composition (type = {ty:?})"))?,
				ProtoNodeInput::Node(_, _) => f.write_str("Node")?,
			}
			f.write_str("\n")?;

			match &node.construction_args {
				ConstructionArgs::Value(value) => {
					f.write_str(&"\t".repeat(indent + 1))?;
					f.write_fmt(format_args!("Value construction argument: {value:?}"))?
				}
				ConstructionArgs::Nodes(nodes) => {
					for id in nodes {
						write_node(f, network, id.0, indent + 1)?;
					}
				}
				ConstructionArgs::Inline(inline) => {
					f.write_str(&"\t".repeat(indent + 1))?;
					f.write_fmt(format_args!("Inline construction argument: {inline:?}"))?
				}
			}
			f.write_str(&"\t".repeat(indent))?;
			f.write_str("}\n")?;
			Ok(())
		}

		let id = self.output;
		write_node(f, self, id, 0)
	}
}

#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Debug, Clone)]
/// Defines the arguments used to construct the boxed node struct. This is used to call the constructor function in the `node_registry.rs` file - which is hidden behind a wall of macros.
pub enum ConstructionArgs {
	/// A value of a type that is known, allowing serialization (serde::Deserialize is not object safe)
	Value(value::TaggedValue),
	// TODO: use a struct for clearer naming.
	/// A list of nodes used as inputs to the constructor function in `node_registry.rs`.
	/// The bool indicates whether to treat the node as lambda node.
	Nodes(Vec<(NodeId, bool)>),
	// TODO: What?
	Inline(InlineRust),
}

impl Eq for ConstructionArgs {}

impl PartialEq for ConstructionArgs {
	fn eq(&self, other: &Self) -> bool {
		match (&self, &other) {
			(Self::Nodes(n1), Self::Nodes(n2)) => n1 == n2,
			(Self::Value(v1), Self::Value(v2)) => v1 == v2,
			_ => {
				use std::hash::Hasher;
				let hash = |input: &Self| {
					let mut hasher = rustc_hash::FxHasher::default();
					input.hash(&mut hasher);
					hasher.finish()
				};
				hash(self) == hash(other)
			}
		}
	}
}

impl Hash for ConstructionArgs {
	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
		core::mem::discriminant(self).hash(state);
		match self {
			Self::Nodes(nodes) => {
				for node in nodes {
					node.hash(state);
				}
			}
			Self::Value(value) => value.hash(state),
			Self::Inline(inline) => inline.hash(state),
		}
	}
}

impl ConstructionArgs {
	// TODO: what? Used in the gpu_compiler crate for something.
	pub fn new_function_args(&self) -> Vec<String> {
		match self {
			ConstructionArgs::Nodes(nodes) => nodes.iter().map(|n| format!("n{:0x}", n.0)).collect(),
			ConstructionArgs::Value(value) => vec![value.to_primitive_string()],
			ConstructionArgs::Inline(inline) => vec![inline.expr.clone()],
		}
	}
}

#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Debug, Clone, PartialEq, Hash, Eq)]
/// A protonode is an intermediate step between the `DocumentNode` and the boxed struct that actually runs the node (found in the [`BorrowTree`]). It has one primary input and several secondary inputs in [`ConstructionArgs`].
pub struct ProtoNode {
	pub construction_args: ConstructionArgs,
	pub input: ProtoNodeInput,
	pub identifier: NodeIdentifier,
	pub document_node_path: Vec<NodeId>,
	pub skip_deduplication: bool,
	pub hash: u64,
}

/// A ProtoNodeInput represents the primary input of a node in a ProtoNetwork.
/// Similar to [`crate::document::NodeInput`].
#[derive(Debug, PartialEq, Eq, Clone, Hash)]
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
pub enum ProtoNodeInput {
	/// [`ProtoNode`]s do not require any input, e.g. the value node just takes in [`ConstructionArgs`].
	None,
	/// A ManualComposition input represents an input that opts out of being resolved through the default `ComposeNode`, which first runs the previous (upstream) node, then passes that evaluated result to this node
	/// Instead, ManualComposition lets this node actually consume the provided input instead of passing it to its predecessor.
	///
	/// Say we have the network `a -> b -> c` where `c` is the output node and `a` is the input node.
	/// We would expect `a` to get input from the network, `b` to get input from `a`, and `c` to get input from `b`.
	/// This could be represented as `f(x) = c(b(a(x)))`. `a` is run with input `x` from the network. `b` is run with input from `a`. `c` is run with input from `b`.
	///
	/// However if `b`'s input is using manual composition, this means it would instead be `f(x) = c(b(x))`. This means that `b` actually gets input from the network, and `a` is not automatically executed as it would be using the default ComposeNode flow.
	ManualComposition(Type),
	/// the bool indicates whether to treat the node as lambda node.
	/// When treating it as a lambda, only the node that is connected itself is fed as input.
	/// Otherwise, the the entire network of which the node is the output is fed as input.
	Node(NodeId, bool),
}

impl ProtoNodeInput {
	pub fn unwrap_node(self) -> NodeId {
		match self {
			ProtoNodeInput::Node(id, _) => id,
			_ => panic!("tried to unwrap id from non node input \n node: {self:#?}"),
		}
	}
}

impl ProtoNode {
	/// A stable node ID is a hash of a node that should stay constant. This is used in order to remove duplicates from the graph.
	/// In the case of `skip_deduplication`, the `document_node_path` is also hashed in order to avoid duplicate monitor nodes from being removed (which would make it impossible to load thumbnails).
	pub fn stable_node_id(&self) -> Option<NodeId> {
		use std::hash::Hasher;
		let mut hasher = rustc_hash::FxHasher::default();

		self.identifier.name.hash(&mut hasher);
		self.construction_args.hash(&mut hasher);
		if self.skip_deduplication {
			self.document_node_path.hash(&mut hasher);
		}
		self.hash.hash(&mut hasher);
		std::mem::discriminant(&self.input).hash(&mut hasher);
		match self.input {
			ProtoNodeInput::None => (),
			ProtoNodeInput::ManualComposition(ref ty) => {
				ty.hash(&mut hasher);
			}
			ProtoNodeInput::Node(id, lambda) => (id, lambda).hash(&mut hasher),
		};
		Some(hasher.finish() as NodeId)
	}

	/// Construct a new [`ProtoNode`] with the specified construction args and a `ClonedNode` implementation.
	pub fn value(value: ConstructionArgs, path: Vec<NodeId>) -> Self {
		Self {
			identifier: NodeIdentifier::new("graphene_core::value::ClonedNode"),
			construction_args: value,
			input: ProtoNodeInput::None,
			document_node_path: path,
			skip_deduplication: false,
			hash: 0,
		}
	}

	/// Converts all references to other node IDs into new IDs by running the specified function on them.
	/// This can be used when changing the IDs of the nodes, for example in the case of generating stable IDs.
	pub fn map_ids(&mut self, f: impl Fn(NodeId) -> NodeId, skip_lambdas: bool) {
		if let ProtoNodeInput::Node(id, lambda) = self.input {
			if !(skip_lambdas && lambda) {
				self.input = ProtoNodeInput::Node(f(id), lambda)
			}
		}
		if let ConstructionArgs::Nodes(ids) = &mut self.construction_args {
			ids.iter_mut().filter(|(_, lambda)| !(skip_lambdas && *lambda)).for_each(|(id, _)| *id = f(*id));
		}
	}

	pub fn unwrap_construction_nodes(&self) -> Vec<(NodeId, bool)> {
		match &self.construction_args {
			ConstructionArgs::Nodes(nodes) => nodes.clone(),
			_ => panic!("tried to unwrap nodes from non node construction args \n node: {self:#?}"),
		}
	}
}

impl ProtoNetwork {
	fn check_ref(&self, ref_id: &NodeId, id: &NodeId) {
		assert!(
			self.nodes.iter().any(|(check_id, _)| check_id == ref_id),
			"Node id:{id} has a reference which uses node id:{ref_id} which doesn't exist in network {self:#?}"
		);
	}

	/// Construct a hashmap containing a list of the nodes that depend on this proto network.
	pub fn collect_outwards_edges(&self) -> HashMap<NodeId, Vec<NodeId>> {
		let mut edges: HashMap<NodeId, Vec<NodeId>> = HashMap::new();
		for (id, node) in &self.nodes {
			if let ProtoNodeInput::Node(ref_id, _) = &node.input {
				self.check_ref(ref_id, id);
				edges.entry(*ref_id).or_default().push(*id)
			}
			if let ConstructionArgs::Nodes(ref_nodes) = &node.construction_args {
				for (ref_id, _) in ref_nodes {
					self.check_ref(ref_id, id);
					edges.entry(*ref_id).or_default().push(*id)
				}
			}
		}
		edges
	}

	/// Convert all node IDs to be stable (based on the hash generated by [`ProtoNode::stable_node_id`]).
	/// This function requires that the graph be topologically sorted.
	pub fn generate_stable_node_ids(&mut self) {
		debug_assert!(self.is_topologically_sorted());
		let outwards_edges = self.collect_outwards_edges();

		for index in 0..self.nodes.len() {
			let Some(sni) = self.nodes[index].1.stable_node_id() else {
				panic!("failed to generate stable node id for node {:#?}", self.nodes[index].1);
			};
			self.replace_node_id(&outwards_edges, index as NodeId, sni, false);
			self.nodes[index].0 = sni as NodeId;
		}
	}

	/// Create a hashmap with the list of nodes this proto network depends on/uses as inputs.
	pub fn collect_inwards_edges(&self) -> HashMap<NodeId, Vec<NodeId>> {
		let mut edges: HashMap<NodeId, Vec<NodeId>> = HashMap::new();
		for (id, node) in &self.nodes {
			if let ProtoNodeInput::Node(ref_id, _) = &node.input {
				self.check_ref(ref_id, id);
				edges.entry(*id).or_default().push(*ref_id)
			}
			if let ConstructionArgs::Nodes(ref_nodes) = &node.construction_args {
				for (ref_id, _) in ref_nodes {
					self.check_ref(ref_id, id);
					edges.entry(*id).or_default().push(*ref_id)
				}
			}
		}
		edges
	}

	/// Inserts a [`graphene_core::structural::ComposeNode`] for each node that has a [`ProtoNodeInput::Node`]. The compose node evaluates the first node, and then sends the result into the second node.
	pub fn resolve_inputs(&mut self) -> Result<(), String> {
		// Perform topological sort once
		self.reorder_ids()?;

		let max_id = self.nodes.len() as NodeId - 1;

		// Collect outward edges once
		let outwards_edges = self.collect_outwards_edges();

		// Iterate over nodes in topological order
		for node_id in 0..=max_id {
			let node = &mut self.nodes[node_id as usize].1;

			if let ProtoNodeInput::Node(input_node_id, false) = node.input {
				// Create a new node that composes the current node and its input node
				let compose_node_id = self.nodes.len() as NodeId;
				let input = self.nodes[input_node_id as usize].1.input.clone();
				let mut path = self.nodes[input_node_id as usize].1.document_node_path.clone();
				path.push(node_id);

				self.nodes.push((
					compose_node_id,
					ProtoNode {
						identifier: NodeIdentifier::new("graphene_core::structural::ComposeNode<_, _, _>"),
						construction_args: ConstructionArgs::Nodes(vec![(input_node_id, false), (node_id, true)]),
						input,
						document_node_path: path,
						skip_deduplication: false,
						hash: 0,
					},
				));

				self.replace_node_id(&outwards_edges, node_id, compose_node_id, true);
			}
		}
		self.reorder_ids()?;
		Ok(())
	}

	/// Update all of the references to a node ID in the graph with a new ID named `compose_node_id`.
	fn replace_node_id(&mut self, outwards_edges: &HashMap<u64, Vec<u64>>, node_id: u64, compose_node_id: u64, skip_lambdas: bool) {
		// Update references in other nodes to use the new compose node
		if let Some(referring_nodes) = outwards_edges.get(&node_id) {
			for &referring_node_id in referring_nodes {
				let referring_node = &mut self.nodes[referring_node_id as usize].1;
				referring_node.map_ids(|id| if id == node_id { compose_node_id } else { id }, skip_lambdas)
			}
		}

		if self.output == node_id {
			self.output = compose_node_id;
		}

		self.inputs.iter_mut().for_each(|id| {
			if *id == node_id {
				*id = compose_node_id;
			}
		});
	}
	// Based on https://en.wikipedia.org/wiki/Topological_sorting#Depth-first_search
	// This approach excludes nodes that are not connected
	pub fn topological_sort(&self) -> Result<Vec<NodeId>, String> {
		let mut sorted = Vec::new();
		let inwards_edges = self.collect_inwards_edges();
		fn visit(node_id: NodeId, temp_marks: &mut HashSet<NodeId>, sorted: &mut Vec<NodeId>, inwards_edges: &HashMap<NodeId, Vec<NodeId>>, network: &ProtoNetwork) -> Result<(), String> {
			if sorted.contains(&node_id) {
				return Ok(());
			};
			if temp_marks.contains(&node_id) {
				return Err(format!("Cycle detected {inwards_edges:#?}, {network:#?}"));
			}

			if let Some(dependencies) = inwards_edges.get(&node_id) {
				temp_marks.insert(node_id);
				for &dependant in dependencies {
					visit(dependant, temp_marks, sorted, inwards_edges, network)?;
				}
				temp_marks.remove(&node_id);
			}
			sorted.push(node_id);
			Ok(())
		}

		if !self.nodes.iter().any(|(id, _)| *id == self.output) {
			return Err(format!("Output id {} does not exist", self.output));
		}
		visit(self.output, &mut HashSet::new(), &mut sorted, &inwards_edges, self)?;
		Ok(sorted)
	}

	fn is_topologically_sorted(&self) -> bool {
		let mut visited = HashSet::new();

		let inwards_edges = self.collect_inwards_edges();
		for (id, _) in &self.nodes {
			for &dependency in inwards_edges.get(id).unwrap_or(&Vec::new()) {
				if !visited.contains(&dependency) {
					dbg!(id, dependency);
					dbg!(&visited);
					dbg!(&self.nodes);
					return false;
				}
			}
			visited.insert(*id);
		}
		true
	}

	/*// Based on https://en.wikipedia.org/wiki/Topological_sorting#Kahn's_algorithm
	pub fn topological_sort(&self) -> Vec<NodeId> {
		let mut sorted = Vec::new();
		let outwards_edges = self.collect_outwards_edges();
		let mut inwards_edges = self.collect_inwards_edges();
		let mut no_incoming_edges: Vec<_> = self.nodes.iter().map(|entry| entry.0).filter(|id| !inwards_edges.contains_key(id)).collect();

		assert_ne!(no_incoming_edges.len(), 0, "Acyclic graphs must have at least one node with no incoming edge");

		while let Some(node_id) = no_incoming_edges.pop() {
			sorted.push(node_id);

			if let Some(outwards_edges) = outwards_edges.get(&node_id) {
				for &ref_id in outwards_edges {
					let dependencies = inwards_edges.get_mut(&ref_id).unwrap();
					dependencies.retain(|&id| id != node_id);
					if dependencies.is_empty() {
						no_incoming_edges.push(ref_id)
					}
				}
			}
		}
		debug!("Sorted order {sorted:?}");
		sorted
	}*/

	/// Sort the nodes vec so it is in a topological order. This ensures that no node takes an input from a node that is found later in the list.
	fn reorder_ids(&mut self) -> Result<(), String> {
		let order = self.topological_sort()?;

		// Map of node ids to their current index in the nodes vector
		let current_positions: HashMap<_, _> = self.nodes.iter().enumerate().map(|(pos, (id, _))| (*id, pos)).collect();

		// Map of node ids to their new index based on topological order
		let new_positions: HashMap<_, _> = order.iter().enumerate().map(|(pos, id)| (*id, pos as NodeId)).collect();

		// Create a new nodes vector based on the topological order
		let mut new_nodes = Vec::with_capacity(order.len());
		for (index, &id) in order.iter().enumerate() {
			let current_pos = *current_positions.get(&id).unwrap();
			new_nodes.push((index as NodeId, self.nodes[current_pos].1.clone()));
		}

		// Update node references to reflect the new order
		new_nodes.iter_mut().for_each(|(_, node)| {
			node.map_ids(|id| *new_positions.get(&id).expect("node not found in lookup table"), false);
		});

		// Update the nodes vector and other references
		self.nodes = new_nodes;
		self.inputs = self.inputs.iter().filter_map(|id| new_positions.get(id).copied()).collect();
		self.output = *new_positions.get(&self.output).unwrap();

		assert_eq!(order.len(), self.nodes.len());
		Ok(())
	}
}

/// The `TypingContext` is used to store the types of the nodes indexed by their stable node id.
#[derive(Default, Clone)]
pub struct TypingContext {
	lookup: Cow<'static, HashMap<NodeIdentifier, HashMap<NodeIOTypes, NodeConstructor>>>,
	inferred: HashMap<NodeId, NodeIOTypes>,
	constructor: HashMap<NodeId, NodeConstructor>,
}

impl TypingContext {
	/// Creates a new `TypingContext` with the given lookup table.
	pub fn new(lookup: &'static HashMap<NodeIdentifier, HashMap<NodeIOTypes, NodeConstructor>>) -> Self {
		Self {
			lookup: Cow::Borrowed(lookup),
			..Default::default()
		}
	}

	/// Updates the `TypingContext` wtih a given proto network. This will infer the types of the nodes
	/// and store them in the `inferred` field. The proto network has to be topologically sorted
	/// and contain fully resolved stable node ids.
	pub fn update(&mut self, network: &ProtoNetwork) -> Result<(), String> {
		for (id, node) in network.nodes.iter() {
			self.infer(*id, node)?;
		}
		Ok(())
	}

	/// Returns the node constructor for a given node id.
	pub fn constructor(&self, node_id: NodeId) -> Option<NodeConstructor> {
		self.constructor.get(&node_id).copied()
	}

	/// Returns the type of a given node id if it exists
	pub fn type_of(&self, node_id: NodeId) -> Option<&NodeIOTypes> {
		self.inferred.get(&node_id)
	}

	/// Returns the inferred types for a given node id.
	pub fn infer(&mut self, node_id: NodeId, node: &ProtoNode) -> Result<NodeIOTypes, String> {
		let identifier = node.identifier.name.clone();

		// Return the inferred type if it is already known
		if let Some(infered) = self.inferred.get(&node_id) {
			return Ok(infered.clone());
		}

		let parameters = match node.construction_args {
			// If the node has a value parameter we can infer the return type from it
			ConstructionArgs::Value(ref v) => {
				assert!(matches!(node.input, ProtoNodeInput::None));
				// TODO: This should return a reference to the value
				let types = NodeIOTypes::new(concrete!(()), v.ty(), vec![v.ty()]);
				self.inferred.insert(node_id, types.clone());
				return Ok(types);
			}
			// If the node has nodes as parameters we can infer the types from the node outputs
			ConstructionArgs::Nodes(ref nodes) => nodes
				.iter()
				.map(|(id, _)| {
					self.inferred
						.get(id)
						.ok_or(format!("Inferring type of {node_id} depends on {id} which is not present in the typing context"))
						.map(|node| node.ty())
				})
				.collect::<Result<Vec<Type>, String>>()?,
			ConstructionArgs::Inline(ref inline) => vec![inline.ty.clone()],
		};

		// Get the node input type from the proto node declaration
		let input = match node.input {
			ProtoNodeInput::None => concrete!(()),
			ProtoNodeInput::ManualComposition(ref ty) => ty.clone(),
			ProtoNodeInput::Node(id, _) => {
				let input = self
					.inferred
					.get(&id)
					.ok_or(format!("Inferring type of {node_id} depends on {id} which is not present in the typing context"))?;
				input.output.clone()
			}
		};
		let impls = self
			.lookup
			.get(&node.identifier)
			.ok_or(format!("No implementations found for {:?}. Other implementations found {:?}", node.identifier, self.lookup))?;

		if matches!(input, Type::Generic(_)) {
			return Err(format!("Generic types are not supported as inputs yet {:?} occurred in {:?}", input, node.identifier));
		}
		if parameters.iter().any(|p| {
			matches!(p,
			Type::Fn(_, b) if matches!(b.as_ref(), Type::Generic(_)))
		}) {
			return Err(format!("Generic types are not supported in parameters: {:?} occurred in {:?}", parameters, node.identifier));
		}
		fn covariant(from: &Type, to: &Type) -> bool {
			match (from, to) {
				(Type::Concrete(t1), Type::Concrete(t2)) => t1 == t2,
				(Type::Fn(a1, b1), Type::Fn(a2, b2)) => covariant(a1, a2) && covariant(b1, b2),
				// TODO: relax this requirement when allowing generic types as inputs
				(Type::Generic(_), _) => false,
				(_, Type::Generic(_)) => true,
				_ => false,
			}
		}

		// List of all implementations that match the input and parameter types
		let valid_output_types = impls
			.keys()
			.filter(|node_io| covariant(&input, &node_io.input) && parameters.iter().zip(node_io.parameters.iter()).all(|(p1, p2)| covariant(p1, p2) && covariant(p1, p2)))
			.collect::<Vec<_>>();

		// Attempt to substitute generic types with concrete types and save the list of results
		let substitution_results = valid_output_types
			.iter()
			.map(|node_io| {
				collect_generics(node_io)
					.iter()
					.try_for_each(|generic| check_generic(node_io, &input, &parameters, generic).map(|_| ()))
					.map(|_| {
						if let Type::Generic(out) = &node_io.output {
							((*node_io).clone(), check_generic(node_io, &input, &parameters, out).unwrap())
						} else {
							((*node_io).clone(), node_io.output.clone())
						}
					})
			})
			.collect::<Vec<_>>();

		// Collect all substitutions that are valid
		let valid_impls = substitution_results.iter().filter_map(|result| result.as_ref().ok()).collect::<Vec<_>>();

		match valid_impls.as_slice() {
			[] => {
				dbg!(&self.inferred);
				Err(format!(
					"No implementations found for {identifier} with \ninput: {input:?} and \nparameters: {parameters:?}.\nOther Implementations found: {:?}",
					impls.keys().collect::<Vec<_>>(),
				))
			}
			[(org_nio, output)] => {
				let node_io = NodeIOTypes::new(input, (*output).clone(), parameters);

				// Save the inferred type
				self.inferred.insert(node_id, node_io.clone());
				self.constructor.insert(node_id, impls[org_nio]);
				Ok(node_io)
			}
			_ => Err(format!(
				"Multiple implementations found for {identifier} with input {input:?} and parameters {parameters:?} (valid types: {valid_output_types:?}"
			)),
		}
	}
}

/// Returns a list of all generic types used in the node
fn collect_generics(types: &NodeIOTypes) -> Vec<Cow<'static, str>> {
	let inputs = [&types.input].into_iter().chain(types.parameters.iter().flat_map(|x| x.fn_output()));
	let mut generics = inputs
		.filter_map(|t| match t {
			Type::Generic(out) => Some(out.clone()),
			_ => None,
		})
		.collect::<Vec<_>>();
	if let Type::Generic(out) = &types.output {
		generics.push(out.clone());
	}
	generics.dedup();
	generics
}

/// Checks if a generic type can be substituted with a concrete type and returns the concrete type
fn check_generic(types: &NodeIOTypes, input: &Type, parameters: &[Type], generic: &str) -> Result<Type, String> {
	let inputs = [(Some(&types.input), Some(input))]
		.into_iter()
		.chain(types.parameters.iter().map(|x| x.fn_output()).zip(parameters.iter().map(|x| x.fn_output())));
	let concrete_inputs = inputs.filter(|(ni, _)| matches!(ni, Some(Type::Generic(input)) if generic == input));
	let mut outputs = concrete_inputs.flat_map(|(_, out)| out);
	let out_ty = outputs
		.next()
		.ok_or_else(|| format!("Generic output type {generic} is not dependent on input {input:?} or parameters {parameters:?}",))?;
	if outputs.any(|ty| ty != out_ty) {
		return Err(format!("Generic output type {generic} is dependent on multiple inputs or parameters",));
	}
	Ok(out_ty.clone())
}

#[cfg(test)]
mod test {
	use super::*;
	use crate::proto::{ConstructionArgs, ProtoNetwork, ProtoNode, ProtoNodeInput};

	#[test]
	fn topological_sort() {
		let construction_network = test_network();
		let sorted = construction_network.topological_sort().expect("Error when calling 'topological_sort' on 'construction_network.");
		println!("{sorted:#?}");
		assert_eq!(sorted, vec![14, 10, 11, 1]);
	}

	#[test]
	fn topological_sort_with_cycles() {
		let construction_network = test_network_with_cycles();
		let sorted = construction_network.topological_sort();

		assert!(sorted.is_err())
	}

	#[test]
	fn id_reordering() {
		let mut construction_network = test_network();
		construction_network.reorder_ids().expect("Error when calling 'reorder_ids' on 'construction_network.");
		let sorted = construction_network.topological_sort().expect("Error when calling 'topological_sort' on 'construction_network.");
		println!("nodes: {:#?}", construction_network.nodes);
		assert_eq!(sorted, vec![0, 1, 2, 3]);
		let ids: Vec<_> = construction_network.nodes.iter().map(|(id, _)| *id).collect();
		println!("{ids:#?}");
		println!("nodes: {:#?}", construction_network.nodes);
		assert_eq!(construction_network.nodes[0].1.identifier.name.as_ref(), "value");
		assert_eq!(ids, vec![0, 1, 2, 3]);
	}

	#[test]
	fn id_reordering_idempotent() {
		let mut construction_network = test_network();
		construction_network.reorder_ids().expect("Error when calling 'reorder_ids' on 'construction_network.");
		construction_network.reorder_ids().expect("Error when calling 'reorder_ids' on 'construction_network.");
		let sorted = construction_network.topological_sort().expect("Error when calling 'topological_sort' on 'construction_network.");
		assert_eq!(sorted, vec![0, 1, 2, 3]);
		let ids: Vec<_> = construction_network.nodes.iter().map(|(id, _)| *id).collect();
		println!("{ids:#?}");
		assert_eq!(construction_network.nodes[0].1.identifier.name.as_ref(), "value");
		assert_eq!(ids, vec![0, 1, 2, 3]);
	}

	#[test]
	fn input_resolution() {
		let mut construction_network = test_network();
		construction_network.resolve_inputs().expect("Error when calling 'resolve_inputs' on 'construction_network.");
		println!("{construction_network:#?}");
		assert_eq!(construction_network.nodes[0].1.identifier.name.as_ref(), "value");
		assert_eq!(construction_network.nodes.len(), 6);
		assert_eq!(construction_network.nodes[5].1.construction_args, ConstructionArgs::Nodes(vec![(3, false), (4, true)]));
	}

	#[test]
	fn stable_node_id_generation() {
		let mut construction_network = test_network();
		construction_network.resolve_inputs().expect("Error when calling 'resolve_inputs' on 'construction_network.");
		construction_network.generate_stable_node_ids();
		assert_eq!(construction_network.nodes[0].1.identifier.name.as_ref(), "value");
		let ids: Vec<_> = construction_network.nodes.iter().map(|(id, _)| *id).collect();
		assert_eq!(
			ids,
			vec![
				2785293541695324513,
				12994980551665119079,
				17926586814106640907,
				2523412932923113119,
				12965978620570332342,
				16191561097939296982
			]
		);
	}

	fn test_network() -> ProtoNetwork {
		ProtoNetwork {
			inputs: vec![10],
			output: 1,
			nodes: [
				(
					7,
					ProtoNode {
						identifier: "id".into(),
						input: ProtoNodeInput::Node(11, false),
						construction_args: ConstructionArgs::Nodes(vec![]),
						document_node_path: vec![],
						skip_deduplication: false,
					},
				),
				(
					1,
					ProtoNode {
						identifier: "id".into(),
						input: ProtoNodeInput::Node(11, false),
						construction_args: ConstructionArgs::Nodes(vec![]),
						document_node_path: vec![],
						skip_deduplication: false,
					},
				),
				(
					10,
					ProtoNode {
						identifier: "cons".into(),
						input: ProtoNodeInput::ManualComposition(concrete!(u32)),
						construction_args: ConstructionArgs::Nodes(vec![(14, false)]),
						document_node_path: vec![],
						skip_deduplication: false,
					},
				),
				(
					11,
					ProtoNode {
						identifier: "add".into(),
						input: ProtoNodeInput::Node(10, false),
						construction_args: ConstructionArgs::Nodes(vec![]),
						document_node_path: vec![],
						skip_deduplication: false,
					},
				),
				(
					14,
					ProtoNode {
						identifier: "value".into(),
						input: ProtoNodeInput::None,
						construction_args: ConstructionArgs::Value(value::TaggedValue::U32(2)),
						document_node_path: vec![],
						skip_deduplication: false,
					},
				),
			]
			.into_iter()
			.collect(),
		}
	}

	fn test_network_with_cycles() -> ProtoNetwork {
		ProtoNetwork {
			inputs: vec![1],
			output: 1,
			nodes: [
				(
					1,
					ProtoNode {
						identifier: "id".into(),
						input: ProtoNodeInput::Node(2, false),
						construction_args: ConstructionArgs::Nodes(vec![]),
						document_node_path: vec![],
						skip_deduplication: false,
					},
				),
				(
					2,
					ProtoNode {
						identifier: "id".into(),
						input: ProtoNodeInput::Node(1, false),
						construction_args: ConstructionArgs::Nodes(vec![]),
						document_node_path: vec![],
						skip_deduplication: false,
					},
				),
			]
			.into_iter()
			.collect(),
		}
	}
}