use crate::cfg::config::Config;
use crate::pkgtoolkit::pkgtools::Package;
use serde::Deserialize;
use tokio;

/*
use emissary_core::runtime::{
    AsyncRead,
    AsyncWrite,
};
*/

use std::{collections::HashMap, path::Path};
use tokio::io::{AsyncReadExt, AsyncWriteExt, BufReader};
use indicatif::{ProgressBar, ProgressStyle};

use url;
use yosemite::Session;
use yosemite::SessionOptions;

pub struct I2PPackage {
    config: Config,
    index_packages: Option<HashMap<String, Package>>, 
}

#[derive(Deserialize, Debug)]
struct IndexData {
    packages: Vec<Package>, 
}

impl I2PPackage {
    /// Creates a new I2P object with the given configuration.
    ///
    /// # Returns
    ///
    /// A new I2P object with the given configuration. The session is initially set to None and the connected status is set to false.
    pub fn new(config: Config) -> Self {
        I2PPackage { 
            config: config, 
            index_packages: None 
        }
    }

    /// Downloads the INDEX.tar.gz file from the configured repository
    /// and stores it in the configured cache directory.
    ///
    /// # Errors
    ///
    /// Returns an error if the request fails, if the response status is not successful, or if there's an issue while reading or writing the file.
   pub async fn fetch_index(&mut self) -> Result<bool, Box<dyn std::error::Error>> {
        let repo_url_str = &self.config.repo.repo_url;
        let cache_dir = &self.config.paths.cache_dir;

        let url = url::Url::parse(repo_url_str)?;
        let host = url.host_str().ok_or("No host in URL")?;

        let request_path = url.path();
        let request_path = if request_path.ends_with(".tar.gz") {
            request_path.to_string()
        } else {
            format!("{}/INDEX.tar.gz", request_path.trim_end_matches('/'))
        };

        let session_options = SessionOptions::default();
        let mut session = Session::new(session_options).await?;
        let mut stream = session.connect(host).await?;

        let request = format!(
            "GET {} HTTP/1.1\r\nHost: {}\r\nConnection: close\r\n\r\n",
            request_path, host
        );
        stream.write_all(request.as_bytes()).await?;

        let mut reader = BufReader::new(stream);
        let mut response_buffer = Vec::new();
        reader.read_to_end(&mut response_buffer).await?;

        let headers_end = response_buffer
            .windows(4)
            .position(|window| window == b"\r\n\r\n")
            .ok_or("Invalid response: no headers end")?;

        let headers_str = std::str::from_utf8(&response_buffer[..headers_end])?;
        if !headers_str.starts_with("HTTP/1.1 200") && !headers_str.starts_with("HTTP/1.0 200") {
            return Err(format!(
                "HTTP Error: {}",
                headers_str.lines().next().unwrap_or("Unknown")
            ).into());
        }

        let content_length = headers_str
            .lines()
            .find(|line| line.to_lowercase().starts_with("content-length:"))
            .and_then(|line| line.split_at(15).1.trim().parse::<u64>().ok())
            .unwrap_or(0);
        
        let body_start = headers_end + 4;
        let mut body_reader = std::io::Cursor::new(&response_buffer[body_start..]);
        let file_path = Path::new(cache_dir).join("INDEX.tar.gz");


        let pb = if content_length > 0 {
            let pb = ProgressBar::new(content_length);
            pb.set_style(ProgressStyle::default_bar()
                .template("{spinner:.green} [{elapsed_precise}] [{bar:40.cyan/blue}] {bytes}/{total_bytes} ({eta})")?
                .progress_chars("#>-"));
            pb
        } else {
            let pb = ProgressBar::new_spinner();
            pb.set_style(ProgressStyle::default_spinner()
                .template("{spinner:.green} [{elapsed_precise}] Fetching INDEX.tar.gz...")?
            );
            pb
        };

        let mut file = tokio::fs::File::create(&file_path).await?;

        let chunk_size = 8192u64;
        let mut buffer = vec![0; chunk_size as usize];

        loop {

            let bytes_read_result = std::io::Read::read(&mut body_reader, &mut buffer);
            let bytes_read = match bytes_read_result {
                 Ok(n) => n,
                 Err(e) => return Err(e.into()),
            };

            if bytes_read == 0 {
                break;
            }
            file.write_all(&buffer[..bytes_read]).await?;

            pb.inc(bytes_read as u64);

            if bytes_read < chunk_size as usize {
                break;
            }
        }

        pb.finish_with_message("INDEX.tar.gz download finished");

        log::info!("Extracting INDEX.tar.gz to cache directory...");
        Package::extract_archive(&file_path.to_string_lossy())?; 

        let index_toml_path = Path::new(cache_dir).join("INDEX.toml"); 
        if !index_toml_path.exists() {
             log::warn!("INDEX.toml not found in INDEX.tar.gz. Proceeding without index data.");
             self.index_packages = Some(HashMap::new()); 
             return Ok(true);
        }

        let index_content = std::fs::read_to_string(&index_toml_path)?;
        let index_data: IndexData = toml::from_str(&index_content)?;

        let mut package_map = HashMap::new();
        for pkg in index_data.packages {
             // PKG_URL = /repo/package.mesk
             // FULL URL = "http://mesk.anthrill.i2p/i2p/repo/pkg.mesk"
             let base_url = url::Url::parse(&self.config.repo.repo_url)?;
             let full_url = base_url.join(&pkg.url)?;
             let mut pkg_clone = pkg.clone();
             pkg_clone.url = full_url.to_string(); 

             package_map.insert(pkg_clone.name.clone(), pkg_clone);
        }

        self.index_packages = Some(package_map.clone());
        log::info!("Index loaded successfully, {} packages found.", package_map.len());

        Ok(true)
    }


    /// An internal auxiliary function for downloading data and writing it to a file with a progress display.
    ///
    /// # Arguments
    /// * `data' - Byte slice (&[u8]) with data to write.
    /// * `file_path' is the path to the file to write the data to.
    /// * `content_length' is the expected data size (for the progress bar). Maybe 0.
    /// * `description' - Description of the operation for the progress bar.
    ///
    /// # Errors
    ///
    /// Returns an error if there is a problem when creating or writing to a file.
    async fn download_and_write_file_with_progress(
        data: &[u8],
        file_path: &Path,
        content_length: u64,
        description: &str,
    ) -> Result<(), Box<dyn std::error::Error>> {
        // Прогресс-бар для загрузки
        let pb = if content_length > 0 {
            let pb = ProgressBar::new(content_length);
            pb.set_style(ProgressStyle::default_bar()
                .template(&format!("{{spinner:.green}} [{{elapsed_precise}}] [{{bar:40.cyan/blue}}] {{bytes}}/{{total_bytes}} ({} {{eta}})", description))?
                .progress_chars("#>-"));
            pb
        } else {
            let pb = ProgressBar::new_spinner();
            pb.set_style(ProgressStyle::default_spinner()
                .template(&format!("{{spinner:.green}} [{{elapsed_precise}}] {}...", description))?
            );
            pb
        };

        let mut file = tokio::fs::File::create(&file_path).await?;

        let chunk_size = 8192usize;
        let mut pos = 0;

        while pos < data.len() {
            let end = std::cmp::min(pos + chunk_size, data.len());
            let chunk = &data[pos..end];
            file.write_all(chunk).await?;
            pb.inc(chunk.len() as u64);
            pos = end;
        }

        pb.finish_with_message(format!("{} download finished", description));
        Ok(())
    }

    /// Fetches a specific package identified by `index` (likely the package name).
    /// Assumes `fetch_index` has been called and `self.index_packages` is populated.
    pub fn fetch_package_info(&self, package_name: &str) -> Result<&Package, Box<dyn std::error::Error>> {
        let packages = self.index_packages.as_ref()
            .ok_or("Index not loaded. Call fetch_index first.")?;
        let pkg_info = packages.get(package_name)
            .ok_or(format!("Package '{}' not found in index.", package_name))?;
        Ok(pkg_info)
    }

    /// Fetches a specific package identified by `package_name`.
    /// Assumes `fetch_index` has been called and `self.index_packages` is populated to get the URL.
    /// Downloads the package file (.mesk) to the cache directory.
    ///
    /// # Errors
    ///
    /// Returns an error if the index is not loaded, the package is not found in the index,
    /// the package URL is invalid, the request fails, or if there's an issue writing the file.
    /// Why didn't I just abstract the download functionality into a separate function initially? 
    /// Yes, I'm scared to work with fetch_index, even I don't often write such shit code.
    pub async fn fetch_package(&self, package_name: &str) -> Result<bool, Box<dyn std::error::Error>> {
        let package_info = self.fetch_package_info(package_name)?;
        let url = url::Url::parse(&package_info.url)?;
        let host = url.host_str().ok_or("No host in package URL")?;
        let request_path = url.path();

        let session_options = SessionOptions::default();
        let mut session = Session::new(session_options).await?;
        let mut stream = session.connect(host).await?;

        let request = format!(
            "GET {} HTTP/1.1\r\nHost: {}\r\nConnection: close\r\n\r\n",
            request_path, host
        );
        stream.write_all(request.as_bytes()).await?;

        let mut reader = BufReader::new(stream);
        let mut response_buffer = Vec::new();
        reader.read_to_end(&mut response_buffer).await?;

        let headers_end = response_buffer
            .windows(4)
            .position(|window| window == b"\r\n\r\n")
            .ok_or("Invalid response: no headers end")?;

        let headers_str = std::str::from_utf8(&response_buffer[..headers_end])?;
        if !headers_str.starts_with("HTTP/1.1 200") && !headers_str.starts_with("HTTP/1.0 200") {
            return Err(format!(
                "HTTP Error: {}",
                headers_str.lines().next().unwrap_or("Unknown")
            ).into());
        }

        let content_length = headers_str
            .lines()
            .find(|line| line.to_lowercase().starts_with("content-length:"))
            .and_then(|line| line.split_at(15).1.trim().parse::<u64>().ok())
            .unwrap_or(0);

        let body_start = headers_end + 4;
        let body_bytes = &response_buffer[body_start..];

        let file_name = Path::new(request_path)
            .file_name()
            .ok_or("Could not determine filename from URL path")?
            .to_str()
            .ok_or("Filename is not valid UTF-8")?;
        let cache_dir = &self.config.paths.cache_dir;
        let file_path = Path::new(cache_dir).join(file_name);

        Self::download_and_write_file_with_progress(body_bytes, &file_path, content_length, file_name).await?;

        log::info!("Package '{}' downloaded successfully to {:?}", package_name, file_path);
        Ok(true)
    }
}