use rand::{Rng, rng};
use sha2::{Digest, Sha256};
use std::collections::HashMap;
use std::hash::{DefaultHasher, Hash, Hasher};

use std::fs::{File, OpenOptions, create_dir};
use std::io::{self, Write};

use std::env;

// --- Constants ---
pub const MAX_CHUNK_DATA_SIZE: usize = 1024;
pub const MAX_DIRECTORY_ENTRIES: usize = 16;
pub const MAX_BIG_CHILDREN: usize = 32;
pub const MIN_BIG_CHILDREN: usize = 2;
pub const FILENAME_HASH_SIZE: usize = 32;
pub const DIRECTORY_ENTRY_SIZE: usize = FILENAME_HASH_SIZE * 2; // 64 bytes

pub type NodeHash = [u8; FILENAME_HASH_SIZE];

pub fn node_hash_to_hex_string(hash: &NodeHash) -> String {
    hash.iter().map(|b| format!("{:02x}", b)).collect()
}

#[repr(u8)]
#[derive(Debug, Clone)]
pub enum MerkleNode {
    // up to 1024 bytes of raw data.
    Chunk(ChunkNode) = 0,
    // 0 to 16 directory entries.
    Directory(DirectoryNode) = 1,
    // list of 2 to 32 hashes pointing to Chunk or Big nodes.
    Big(BigNode) = 3,
    // list of 2 to 32 hashes pointing to Directory or BigDirectory nodes.
    BigDirectory(BigDirectoryNode) = 4,
}

#[derive(Debug, Clone)]
pub struct MerkleTree {
    pub data: HashMap<NodeHash, MerkleNode>,
    pub root: NodeHash,
}

impl MerkleTree {
    pub fn new(data: HashMap<NodeHash, MerkleNode>, root: NodeHash) -> MerkleTree {
        MerkleTree { data, root }
    }
}

#[derive(Debug, Clone)]
pub struct ChunkNode {
    pub data: Vec<u8>,
}
impl ChunkNode {
    pub fn new(data: Vec<u8>) -> Result<Self, String> {
        if data.len() > MAX_CHUNK_DATA_SIZE {
            return Err(format!("Chunk data exceeds {} bytes", data.len()));
        }
        Ok(ChunkNode { data })
    }

    pub fn new_random() -> Self {
        let mut rng = rand::rng();

        // Determine a random length between 1 and MAX_CHUNK_DATA_SIZE (inclusive).
        // Using +1 ensures the range is up to 1024.
        let random_len = rng.random_range(1..=MAX_CHUNK_DATA_SIZE);

        // Initialize a vector with the random length
        let mut data = vec![0u8; random_len];

        // Fill the vector with random bytes
        rng.fill(&mut data[..]);

        // Since we generated the length based on MAX_CHUNK_DATA_SIZE,
        // this is guaranteed to be valid and doesn't need to return a Result.
        ChunkNode { data }
    }
}

// Helper struct
#[derive(Debug, Clone)]
pub struct DirectoryEntry {
    pub filename: [u8; FILENAME_HASH_SIZE],
    pub content_hash: NodeHash,
}

pub fn filename_to_string(filename: [u8; FILENAME_HASH_SIZE]) -> String {
    let end_index = filename
        .iter()
        .position(|&b| b == 0)
        .unwrap_or(FILENAME_HASH_SIZE);
    String::from_utf8_lossy(&filename[..end_index]).to_string()
}

#[derive(Debug, Clone)]
pub struct DirectoryNode {
    pub entries: Vec<DirectoryEntry>,
}

impl DirectoryNode {
    pub fn new(entries: Vec<DirectoryEntry>) -> Result<Self, String> {
        if entries.len() > MAX_DIRECTORY_ENTRIES {
            return Err(format!("Directory exceeds {} bytes", entries.len()));
        }
        Ok(DirectoryNode { entries })
    }
}

#[derive(Debug, Clone)]
pub struct BigNode {
    pub children_hashes: Vec<NodeHash>,
}

impl BigNode {
    pub fn new(children_hashes: Vec<NodeHash>) -> Result<Self, String> {
        let n = children_hashes.len();
        if n < MIN_BIG_CHILDREN || n > MAX_BIG_CHILDREN {
            return Err(format!(
                "Big node must have between {} and {} children, found {}",
                MIN_BIG_CHILDREN, MAX_BIG_CHILDREN, n
            ));
        }
        Ok(BigNode { children_hashes })
    }
}

#[derive(Debug, Clone)]
pub struct BigDirectoryNode {
    pub children_hashes: Vec<NodeHash>,
    // pub children_hashes: Vec<DirectoryEntry>,
}

impl BigDirectoryNode {
    pub fn new(children_hashes: Vec<NodeHash>) -> Result<Self, String> {
        let n = children_hashes.len();
        if n < MIN_BIG_CHILDREN || n > MAX_BIG_CHILDREN {
            return Err(format!(
                "BigDirectory node must have between {} and {} children, found {}",
                MIN_BIG_CHILDREN, MAX_BIG_CHILDREN, n
            ));
        }
        Ok(BigDirectoryNode { children_hashes })
    }
}

impl MerkleNode {
    pub fn get_type_byte(&self) -> u8 {
        match self {
            MerkleNode::Chunk(_) => 0,
            MerkleNode::Directory(_) => 1,
            MerkleNode::Big(_) => 3,
            MerkleNode::BigDirectory(_) => 4,
        }
    }

    pub fn serialize(&self) -> Vec<u8> {
        let mut bytes = Vec::new();
        bytes.push(self.get_type_byte());

        match self {
            MerkleNode::Chunk(node) => {
                bytes.extend_from_slice(&node.data);
            }
            MerkleNode::Directory(node) => {
                for entry in &node.entries {
                    bytes.extend_from_slice(&entry.filename);
                    bytes.extend_from_slice(&entry.content_hash);
                }
            }
            MerkleNode::Big(node) => {
                for hash in &node.children_hashes {
                    bytes.extend_from_slice(hash);
                }
            }
            MerkleNode::BigDirectory(node) => {
                for hash in &node.children_hashes {
                    bytes.extend_from_slice(hash);
                }
            }
        }
        bytes
    }
}

fn hash(data: &[u8]) -> NodeHash {
    let root_hash = Sha256::digest(&data);
    println!("root hash: {:?}", root_hash);
    let res: NodeHash = root_hash.try_into().expect("incorrect size");
    res
    /*let mut hasher = DefaultHasher::new();
    data.hash(&mut hasher);
    let hash_u64 = hasher.finish();

    let mut hash_array = [0u8; FILENAME_HASH_SIZE];
    // Simple way to spread a 64-bit hash across 32 bytes for a unique-ish ID
    for i in 0..8 {
        hash_array[i] = (hash_u64 >> (i * 8)) as u8;
    }
    hash_array // The rest remains 0, satisfying the 32-byte requirement
    */
}

fn generate_random_filename() -> [u8; FILENAME_HASH_SIZE] {
    let mut rng = rand::rng();
    let mut filename_bytes = [0; FILENAME_HASH_SIZE];

    // Generate a random length for the base name
    let name_len = rng.random_range(5..21);

    // Generate random alphanumeric characters
    for i in 0..name_len {
        let char_code = rng.random_range(97..123); // 'a' through 'z'
        if i < FILENAME_HASH_SIZE {
            filename_bytes[i] = char_code as u8;
        }
    }

    // Append a common extension
    let ext = if rng.random_bool(0.5) { ".txt" } else { ".dat" };
    let ext_bytes = ext.as_bytes();
    let start_index = name_len.min(FILENAME_HASH_SIZE - ext_bytes.len());
    if start_index < FILENAME_HASH_SIZE {
        filename_bytes[start_index..(start_index + ext_bytes.len())].copy_from_slice(ext_bytes);
    }

    filename_bytes
}

fn generate_random_file_node(
    storage: &mut HashMap<NodeHash, MerkleNode>,
) -> Result<NodeHash, String> {
    let mut rng = rng();
    let is_big = rng.random_bool(0.2); // 20% chance of being a big file

    if !is_big {
        // Generate a simple Chunk Node
        let node = MerkleNode::Chunk(ChunkNode::new_random());
        let hash = hash(&node.serialize());
        storage.insert(hash, node);
        Ok(hash)
    } else {
        // Generate a Big Node (a file composed of chunks)
        let num_children = rng.random_range(MIN_BIG_CHILDREN..=MAX_BIG_CHILDREN.min(8)); // Limit complexity
        let mut children_hashes = Vec::with_capacity(num_children);

        for _ in 0..num_children {
            // Children must be Chunk or Big; for simplicity, we only generate Chunk children here.
            let chunk_node = MerkleNode::Chunk(ChunkNode::new_random());
            let chunk_hash = hash(&chunk_node.serialize());
            storage.insert(chunk_hash, chunk_node);
            children_hashes.push(chunk_hash);
        }

        let node = MerkleNode::Big(BigNode::new(children_hashes)?);
        let hash = hash(&node.serialize());
        storage.insert(hash, node);
        Ok(hash)
    }
}

fn generate_random_directory_node(
    depth: u32,
    max_depth: u32,
    storage: &mut HashMap<NodeHash, MerkleNode>,
) -> Result<NodeHash, String> {
    let mut rng = rng();
    let current_depth = depth + 1;
    let is_big_dir = rng.random_bool(0.3) && current_depth < max_depth;

    if !is_big_dir || current_depth >= max_depth {
        // Generate a simple Directory Node (leaf level directory)
        let num_entries = rng.random_range(1..=MAX_DIRECTORY_ENTRIES.min(5)); // Limit directory size for testing
        let mut entries = Vec::with_capacity(num_entries);

        for _ in 0..num_entries {
            if rng.random_bool(0.7) {
                // 70% chance of creating a file (Chunk/Big)
                let file_hash = generate_random_file_node(storage)?;
                let entry = DirectoryEntry {
                    filename: generate_random_filename(),
                    content_hash: file_hash,
                };
                entries.push(entry);
            } else if current_depth < max_depth {
                // 30% chance of creating a subdirectory
                let dir_hash = generate_random_directory_node(current_depth, max_depth, storage)?;

                // Create a basic directory entry name
                let mut filename_bytes = [0; 32];
                let subdir_name = format!("dir_{}", current_depth);
                filename_bytes[..subdir_name.len()].copy_from_slice(subdir_name.as_bytes());

                let entry = DirectoryEntry {
                    filename: filename_bytes,
                    content_hash: dir_hash,
                };
                entries.push(entry);
            }
        }

        let node = MerkleNode::Directory(DirectoryNode::new(entries)?);
        let hash = hash(&node.serialize());
        storage.insert(hash, node);
        Ok(hash)
    } else {
        // Generate a BigDirectory Node (internal directory structure)
        let num_children = rng.random_range(MIN_BIG_CHILDREN..=MAX_BIG_CHILDREN.min(4)); // Limit children count
        let mut children = Vec::with_capacity(num_children);

        for _ in 0..num_children {
            // Children must be Directory or BigDirectory
            let child_hash = generate_random_directory_node(current_depth, max_depth, storage)?;
            children.push(child_hash);
        }

        let node = MerkleNode::BigDirectory(BigDirectoryNode::new(children)?);
        let hash = hash(&node.serialize());
        storage.insert(hash, node);
        Ok(hash)
    }
}

pub fn generate_random_tree(
    max_depth: u32,
) -> Result<(NodeHash, HashMap<NodeHash, MerkleNode>), String> {
    let mut storage = HashMap::new();

    // Start tree generation from the root directory at depth 0
    let root_hash = generate_random_directory_node(0, max_depth, &mut storage)?;

    Ok((root_hash, storage))
}

pub fn generate_base_tree() -> MerkleTree {
    let mut res = HashMap::new();

    let bob_content = "where is bob".to_string().into_bytes();
    let alice_content = "alice".to_string().into_bytes();
    let oscar_content = "oscar is the opponent".to_string().into_bytes();

    let mut children_nodes = Vec::new();
    for i in 0..10 {
        let mut i_nodes = Vec::new();
        for j in 0..10 {
            let node1 = MerkleNode::Chunk(ChunkNode::new(bob_content.clone()).unwrap());
            let hash = hash(&node1.serialize());
            i_nodes.push(hash);
            res.insert(hash, node1);
        }
        let bignode = MerkleNode::Big(BigNode::new(i_nodes).unwrap());
        let hashbig = hash(&bignode.serialize());
        children_nodes.push(hashbig);
        res.insert(hashbig, bignode);
    }

    let bignode = MerkleNode::Big(BigNode::new(children_nodes).unwrap());
    let hashbig = hash(&bignode.serialize());

    let node1 = MerkleNode::Chunk(ChunkNode::new(bob_content).unwrap());
    let hash1 = hash(&node1.serialize());

    let node2 = MerkleNode::Chunk(ChunkNode::new(alice_content).unwrap());
    let hash2 = hash(&node2.serialize());

    //res.insert(hash1, node1);
    //res.insert(hash2, node2);
    res.insert(hashbig, bignode);

    let node3 = MerkleNode::Chunk(ChunkNode::new(oscar_content).unwrap());
    let hash3 = hash(&node3.serialize());

    //res.insert(hash3, node3);

    let dir1 = MerkleNode::Directory(DirectoryNode {
        entries: [DirectoryEntry {
            filename: generate_random_filename(),
            content_hash: hash3,
        }]
        .to_vec(),
    });
    let hash_dir1 = hash(&dir1.serialize());

    //res.insert(hash_dir1, dir1);

    let root = MerkleNode::Directory(DirectoryNode {
        entries: [
            DirectoryEntry {
                filename: generate_random_filename(),
                content_hash: hashbig,
            },
            /*DirectoryEntry {
                filename: generate_random_filename(),
                content_hash: hash2,
            },
            DirectoryEntry {
                filename: generate_random_filename(),
                content_hash: hash_dir1,
            },*/
        ]
        .to_vec(),
    });

    let root_hash = Sha256::digest(&root.serialize());
    println!("root hash: {:?}", root_hash);
    res.insert(root_hash.try_into().expect("incorrect size"), root);

    MerkleTree::new(res, root_hash.try_into().expect("incorrect size"))
}

pub fn node_to_file(tree: &MerkleTree, node: &MerkleNode, path: String, i: u8) {
    match node.clone() {
        MerkleNode::Directory(dir) => {
            if i != 0 {
                let new_path = format!("{}/fold_{}", path.clone(), i);
                match create_dir(new_path.clone()) {
                    Ok(_) => println!("Directory created successfully!"),
                    Err(e) => println!("Failed to create directory: {}", e),
                }
            }
            for entry in dir.entries {
                // creer un fichier pour chaque entry
                if let Ok(filename_str) = String::from_utf8(entry.filename.to_vec()) {
                    let new_name = format!("{}{}", path.clone(), remove_null_bytes(&filename_str));

                    println!("new_name: {}", new_name);
                    let file = OpenOptions::new()
                        .append(true)
                        .create(true)
                        .open(new_name.clone());
                    match file {
                        Ok(mut fileok) => {
                            if let Some(current) = tree.data.get(&entry.content_hash) {
                                big_or_chunk_to_file(&tree, &current, &mut fileok);
                            }
                        }
                        Err(e) => {
                            eprintln!("error creaation file: {}", e);
                        }
                    }
                }
            }
        }
        MerkleNode::BigDirectory(bigdir) => {
            for entry in bigdir.children_hashes.iter() {
                if let Some(current) = tree.data.get(entry) {
                    node_to_file(tree, current, path.clone(), i + 1);
                }
            }
        }
        _ => {
            eprintln!("invalid type of dir");
        }
    }
}

pub fn remove_null_bytes(input: &str) -> String {
    input.chars().filter(|&c| c != '\0').collect()
}

pub fn big_or_chunk_to_file(tree: &MerkleTree, node: &MerkleNode, file: &mut File) {
    match node {
        MerkleNode::Big(big) => {
            for entry in big.children_hashes.iter() {
                if let Some(current) = tree.data.get(entry) {
                    big_or_chunk_to_file(tree, current, file);
                }
            }
        }
        MerkleNode::Chunk(chunk) => {
            println!("wrote data");
            let _ = file.write_all(&chunk.data);
        }
        _ => {
            println!("invalid type of file");
        }
    }
}

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

    ///
    /// creates a cryptographic signature
    ///
    #[test]
    fn test_saving_tree() {
        if let Ok(current_dir) = env::current_dir() {
            println!("Current working directory: {:?}", current_dir);
        }

        println!("--------- tree test starts ------------");

        match create_dir("../Download/") {
            Ok(_) => println!("Directory created successfully!"),
            Err(e) => println!("Failed to create directory: {}", e),
        }
        let tree = generate_base_tree();

        println!("--------- test tree created ------------");
        if let Some(root_node) = tree.data.get(&tree.root) {
            node_to_file(&tree, root_node, "../Download/".to_string(), 0);
        }
    }

    /*#[test]
    fn signing_message() {
        let username = String::from("gamixtreize");
        let crypto_pair = CryptographicSignature::new(username.clone());
        let handshake = HandshakeMessage::hello(0, 12, username);
        let ser = handshake.serialize();
        let signed_message = sign_message(&crypto_pair, &ser);
        println!("unsigned_message: {:?}", ser);
        println!("signed_message: {:?}", signed_message);
    }*/
}