use memorydb::*;
use sha3::*;
use hashdb::*;
use hash::*;
use nibbleslice::*;
use bytes::*;
use rlp::*;
//use log::*;

pub const NULL_RLP: [u8; 1] = [0x80; 1];
pub const SHA3_NULL_RLP: H256 = H256( [0x56, 0xe8, 0x1f, 0x17, 0x1b, 0xcc, 0x55, 0xa6, 0xff, 0x83, 0x45, 0xe6, 0x92, 0xc0, 0xf8, 0x6e, 0x5b, 0x48, 0xe0, 0x1b, 0x99, 0x6c, 0xad, 0xc0, 0x01, 0x62, 0x2f, 0xb5, 0xe3, 0x63, 0xb4, 0x21] );

pub trait Trie {
	fn root(&self) -> &H256;
	fn is_empty(&self) -> bool { *self.root() == SHA3_NULL_RLP }

	// TODO: consider returning &[u8]...
	fn contains(&self, key: &[u8]) -> bool;
	fn at(&self, key: &[u8]) -> Option<&[u8]>;
	fn insert(&mut self, key: &[u8], value: &[u8]);
	fn remove(&mut self, key: &[u8]);
}

enum Operation {
	New(H256, Bytes),
	Delete(H256),
}

struct Diff (Vec<Operation>);

impl Diff {
	fn new() -> Diff { Diff(vec![]) }

	/// Given the RLP that encodes a node, append a reference to that node `out` and leave `diff`
	/// such that the reference is valid, once applied.
	fn new_node(&mut self, rlp: Bytes, out: &mut RlpStream) {
		if rlp.len() >= 32 {
			let rlp_sha3 = rlp.sha3();
			out.append(&rlp_sha3);
			self.0.push(Operation::New(rlp_sha3, rlp));
		}
		else {
			trace!("new_node: inline node {:?}", &rlp);
			out.append_raw(&rlp, 1);
		}
	}

	/// Given the RLP that encodes a now-unused node, leave `diff` in such a state that it is noted.
	fn delete_node_sha3(&mut self, old_sha3: H256) {
		self.0.push(Operation::Delete(old_sha3));
	}

	fn delete_node(&mut self, old: &Rlp) {
		if old.is_data() && old.size() == 32 {
			self.0.push(Operation::Delete(H256::decode(old)));
		}
	}

	fn replace_node(&mut self, old: &Rlp, rlp: Bytes, out: &mut RlpStream) {
		self.delete_node(old);
		self.new_node(rlp, out);
	}
}

pub struct TrieDB {
	db: Box<HashDB>,
	root: H256,
}

impl TrieDB {
	pub fn new_boxed(db_box: Box<HashDB>) -> Self { let mut r = TrieDB{ db: db_box, root: H256::new() }; r.set_root_rlp(&NULL_RLP); r }

	pub fn new<T>(db: T) -> Self where T: HashDB + 'static { Self::new_boxed(Box::new(db)) }

	pub fn new_memory() -> Self { Self::new(MemoryDB::new()) }

	pub fn db(&self) -> &HashDB { self.db.as_ref() }

	fn set_root_rlp(&mut self, root_data: &[u8]) {
		self.db.kill(&self.root);
		self.root = self.db.insert(root_data);
		trace!("set_root_rlp {:?} {:?}", root_data, self.root);
	}

	fn apply(&mut self, diff: Diff) {
		trace!("applying {:?} changes", diff.0.len());
		for d in diff.0.into_iter() {
			match d {
				Operation::Delete(h) => {
					trace!("TrieDB::apply --- {:?}", &h);
					self.db.kill(&h);
				},
				Operation::New(h, d) => {
					trace!("TrieDB::apply +++ {:?} -> {:?}", &h, &d);
					self.db.emplace(h, d);
				}
			}
		}
	}

	fn add(&mut self, key: &NibbleSlice, value: &[u8]) {
		trace!("ADD: {:?} {:?}", key, value);
		// determine what the new root is, insert new nodes and remove old as necessary.
		let mut todo: Diff = Diff::new();
		let root_rlp = self.augmented(self.db.lookup(&self.root).expect("Trie root not found!"), key, value, &mut todo);
		self.apply(todo);
		self.set_root_rlp(&root_rlp);
		trace!("---");
	}

	fn compose_leaf(partial: &NibbleSlice, value: &[u8]) -> Bytes {
		trace!("compose_leaf {:?} {:?} ({:?})", partial, value, partial.encoded(true));
		let mut s = RlpStream::new_list(2);
		s.append(&partial.encoded(true));
		s.append(&value);
		let r = s.out();
		trace!("compose_leaf: -> {:?}", &r);
		r
	}

	fn compose_raw(partial: &NibbleSlice, raw_payload: &[u8], is_leaf: bool) -> Bytes {
		println!("compose_raw {:?} {:?} {:?} ({:?})", partial, raw_payload, is_leaf, partial.encoded(is_leaf));
		let mut s = RlpStream::new_list(2);
		s.append(&partial.encoded(is_leaf));
		s.append_raw(raw_payload, 1);
		let r = s.out();
		println!("compose_raw: -> {:?}", &r);
		r
	}

	fn compose_extension(partial: &NibbleSlice, raw_payload: &[u8]) -> Bytes {
		Self::compose_raw(partial, raw_payload, false)
	}

	/// Return the bytes encoding the node represented by `rlp`. It will be unlinked from
	/// the trie.
	fn take_node<'a, 'rlp_view>(&'a self, rlp: &'rlp_view Rlp<'a>, diff: &mut Diff) -> &'a [u8] where 'a: 'rlp_view {
		if rlp.is_list() {
			trace!("take_node {:?} (inline)", rlp.raw());
			rlp.raw()
		}
		else if rlp.is_data() && rlp.size() == 32 {
			let h = H256::decode(rlp);
			let r = self.db.lookup(&h).expect("Trie root not found!");
			trace!("take_node {:?} (indirect for {:?})", rlp.raw(), r);
			diff.delete_node_sha3(h);
			r
		}
		else {
			panic!("Empty or invalid node given?");
		}
	}

	/// Transform an existing extension or leaf node to an invalid single-entry branch.
	///
	/// **This operation will not insert the new node nor destroy the original.**
	fn transmuted_extension_to_branch(orig_partial: &NibbleSlice, orig_raw_payload: &[u8], diff: &mut Diff) -> Bytes {
		trace!("transmuted_extension_to_branch");
		let mut s = RlpStream::new_list(17);
		assert!(!orig_partial.is_empty());	// extension nodes are not allowed to have empty partial keys.
		let index = orig_partial.at(0);
		// orig is extension - orig_raw_payload is a node itself.
		for i in 0..17 {
			if index == i {
				if orig_partial.len() > 1 {
					// still need an extension
					diff.new_node(Self::compose_extension(&orig_partial.mid(1), orig_raw_payload), &mut s);
				} else {
					// was an extension of length 1 - just redirect the payload into here.
					s.append_raw(orig_raw_payload, 1);
				}
			} else {
				s.append_empty_data();
			}
		}
		s.out()
	}

	fn transmuted_leaf_to_branch(orig_partial: &NibbleSlice, orig_raw_payload: &[u8], diff: &mut Diff) -> Bytes {
		trace!("transmuted_leaf_to_branch");
		let mut s = RlpStream::new_list(17);
		let index = if orig_partial.is_empty() {16} else {orig_partial.at(0)};
		// orig is leaf - orig_raw_payload is data representing the actual value.
		for i in 0..17 {
			if index == i {
				// this is our node.
				diff.new_node(Self::compose_raw(&orig_partial.mid(if i == 16 {0} else {1}), orig_raw_payload, true), &mut s);
			} else {
				s.append_empty_data();
			}
		}
		s.out()
	}

	/// Transform an existing extension or leaf node plus a new partial/value to a two-entry branch.
	///
	/// **This operation will not insert the new node nor destroy the original.**
	fn transmuted_to_branch_and_augmented(&self, orig_is_leaf: bool, orig_partial: &NibbleSlice, orig_raw_payload: &[u8], partial: &NibbleSlice, value: &[u8], diff: &mut Diff) -> Bytes {
		trace!("transmuted_to_branch_and_augmented");
		let intermediate = match orig_is_leaf {
			true => Self::transmuted_leaf_to_branch(orig_partial, orig_raw_payload, diff),
			false => Self::transmuted_extension_to_branch(orig_partial, orig_raw_payload, diff),
		};
		self.augmented(&intermediate, partial, value, diff)
		// TODO: implement without having to make an intermediate representation.
	}

	/// Given a branch node's RLP `orig` together with a `partial` key and `value`, return the
	/// RLP-encoded node that accomodates the trie with the new entry. Mutate `diff` so that
	/// once applied the returned node is valid.
	fn augmented_into_branch(&self, orig: &Rlp, partial: &NibbleSlice, value: &[u8], diff: &mut Diff) -> Bytes {
		trace!("augmented_into_branch");
		let mut s = RlpStream::new_list(17);
		let index = if partial.is_empty() {16} else {partial.at(0) as usize};
		for i in 0usize..17 {
			match (index == i, i) {
				(true, 16) => // leaf entry - just replace.
					{ s.append(&value); },
				(true, i) if orig.at(i).is_empty() => // easy - original had empty slot.
					diff.new_node(Self::compose_leaf(&partial.mid(1), value), &mut s),
				(true, i) => {	// harder - original has something there already
					let new = self.augmented(orig.at(i).raw(), &partial.mid(1), value, diff);
					diff.replace_node(&orig.at(i), new, &mut s);
				}
				(false, i) => { s.append_raw(orig.at(i).raw(), 1); },
			}
		}
		s.out()
	}

	/// Determine the RLP of the node, assuming we're inserting `partial` into the
	/// node currently of data `old`. This will *not* delete any hash of `old` from the database;
	/// it will just return the new RLP that includes the new node.
	///
	/// The database will be updated so as to make the returned RLP valid through inserting
	/// and deleting nodes as necessary.
	///
	/// **This operation will not insert the new node now destroy the original.**
	fn augmented(&self, old: &[u8], partial: &NibbleSlice, value: &[u8], diff: &mut Diff) -> Bytes {
		trace!("augmented ({:?}, {:?}, {:?})", old, partial, value);
		// already have an extension. either fast_forward, cleve or transmute_to_branch.
		let old_rlp = Rlp::new(old);
		match old_rlp.prototype() {
			Prototype::List(17) => {
				trace!("branch: ROUTE,AUGMENT");
				// already have a branch. route and augment.
				self.augmented_into_branch(&old_rlp, partial, value, diff)
			},
			Prototype::List(2) => {
				let existing_key_rlp = old_rlp.at(0);
				let (existing_key, is_leaf) = NibbleSlice::from_encoded(existing_key_rlp.data());
				match partial.common_prefix(&existing_key) {
					cp if partial.len() == existing_key.len() && cp == existing_key.len() && is_leaf => {
						// equivalent-leaf: replace
						trace!("equivalent-leaf: REPLACE");
						Self::compose_leaf(partial, value)
					},
					0 => {
						// one of us isn't empty: transmute to branch here
						trace!("no-common-prefix, not-both-empty (exist={:?}; new={:?}): TRANSMUTE,AUGMENT", existing_key.len(), partial.len());
						self.transmuted_to_branch_and_augmented(is_leaf, &existing_key, old_rlp.at(1).raw(), partial, value, diff)
					},
					cp if cp == existing_key.len() => {
						trace!("complete-prefix (cp={:?}): AUGMENT-AT-END", cp);
						// fully-shared prefix for this extension:
						// skip to the end of this extension and continue to augment there.
						let n = self.take_node(&old_rlp.at(1), diff);
						let downstream_node = self.augmented(n, &partial.mid(cp), value, diff);
						let mut s = RlpStream::new_list(2);
						s.append_raw(old_rlp.at(0).raw(), 1);
						diff.new_node(downstream_node, &mut s);
						s.out()
					},
					cp => {
						// partially-shared prefix for this extension:
						// split into two extensions, high and low, pass the
						// low through augment with the value before inserting the result
						// into high to create the new.

						// TODO: optimise by doing this without creating augmented_low.

						trace!("partially-shared-prefix (exist={:?}; new={:?}; cp={:?}): AUGMENT-AT-END", existing_key.len(), partial.len(), cp);

						// low (farther from root)
						let low = Self::compose_raw(&existing_key.mid(cp), old_rlp.at(1).raw(), is_leaf);
						let augmented_low = self.augmented(&low, &partial.mid(cp), value, diff);

						// high (closer to root)
						let mut s = RlpStream::new_list(2);
						s.append(&existing_key.encoded_leftmost(cp, false));
						diff.new_node(augmented_low, &mut s);
						s.out()
					},
				}
			},
			Prototype::Data(0) => {
				trace!("empty: COMPOSE");
				Self::compose_leaf(partial, value)
			},
			_ => panic!("Invalid RLP for node."),
		}
	}
}

impl Trie for TrieDB {
	fn root(&self) -> &H256 { &self.root }

	fn contains(&self, _key: &[u8]) -> bool {
		unimplemented!();
	}

	fn at(&self, _key: &[u8]) -> Option<&[u8]> {
		unimplemented!();
	}

	fn insert(&mut self, key: &[u8], value: &[u8]) {
		self.add(&NibbleSlice::new(key), value);
	}

	fn remove(&mut self, _key: &[u8]) {
		unimplemented!();
	}
}

#[cfg(test)]
mod tests {
	use triehash::*;
	use super::*;
	use env_logger;

	#[test]
	fn playpen() {
		env_logger::init().unwrap();

		let big_value = b"00000000000000000000000000000000";

		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], big_value);
		t.insert(&[0x11u8, 0x23], big_value);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![0x01u8, 0x23], big_value.to_vec()),
			(vec![0x11u8, 0x23], big_value.to_vec())
		]));
	}

	#[test]
	fn init() {
		let t = TrieDB::new_memory();
		assert_eq!(*t.root(), SHA3_NULL_RLP);
		assert!(t.is_empty());
	}

	#[test]
	fn insert_on_empty() {
		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
		assert_eq!(*t.root(), trie_root(vec![ (vec![0x01u8, 0x23], vec![0x01u8, 0x23]) ]));
	}

	#[test]
	fn insert_replace_root() {
		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
		t.insert(&[0x01u8, 0x23], &[0x23u8, 0x45]);
		assert_eq!(*t.root(), trie_root(vec![ (vec![0x01u8, 0x23], vec![0x23u8, 0x45]) ]));
	}

	#[test]
	fn insert_make_branch_root() {
		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
		t.insert(&[0x11u8, 0x23], &[0x11u8, 0x23]);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![0x01u8, 0x23], vec![0x01u8, 0x23]),
			(vec![0x11u8, 0x23], vec![0x11u8, 0x23])
		]));
	}

	#[test]
	fn insert_into_branch_root() {
		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
		t.insert(&[0xf1u8, 0x23], &[0xf1u8, 0x23]);
		t.insert(&[0x81u8, 0x23], &[0x81u8, 0x23]);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![0x01u8, 0x23], vec![0x01u8, 0x23]),
			(vec![0x81u8, 0x23], vec![0x81u8, 0x23]),
			(vec![0xf1u8, 0x23], vec![0xf1u8, 0x23]),
		]));
	}

	#[test]
	fn insert_value_into_branch_root() {
		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
		t.insert(&[], &[0x0]);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![], vec![0x0]),
			(vec![0x01u8, 0x23], vec![0x01u8, 0x23]),
		]));
	}

	#[test]
	fn insert_split_leaf() {
		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], &[0x01u8, 0x23]);
		t.insert(&[0x01u8, 0x34], &[0x01u8, 0x34]);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![0x01u8, 0x23], vec![0x01u8, 0x23]),
			(vec![0x01u8, 0x34], vec![0x01u8, 0x34]),
		]));
	}

	#[test]
	fn insert_split_extenstion() {
		let mut t = TrieDB::new_memory();
		t.insert(&[0x01, 0x23, 0x45], &[0x01]);
		t.insert(&[0x01, 0xf3, 0x45], &[0x02]);
		t.insert(&[0x01, 0xf3, 0xf5], &[0x03]);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![0x01, 0x23, 0x45], vec![0x01]),
			(vec![0x01, 0xf3, 0x45], vec![0x02]),
			(vec![0x01, 0xf3, 0xf5], vec![0x03]),
		]));
	}

	#[test]
	fn insert_big_value() {
		let big_value0 = b"00000000000000000000000000000000";
		let big_value1 = b"11111111111111111111111111111111";

		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], big_value0);
		t.insert(&[0x11u8, 0x23], big_value1);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![0x01u8, 0x23], big_value0.to_vec()),
			(vec![0x11u8, 0x23], big_value1.to_vec())
		]));
	}

	#[test]
	fn insert_duplicate_value() {
		let big_value = b"00000000000000000000000000000000";

		let mut t = TrieDB::new_memory();
		t.insert(&[0x01u8, 0x23], big_value);
		t.insert(&[0x11u8, 0x23], big_value);
		assert_eq!(*t.root(), trie_root(vec![
			(vec![0x01u8, 0x23], big_value.to_vec()),
			(vec![0x11u8, 0x23], big_value.to_vec())
		]));
	}
}