use crate::{
    lockfile::{DependencyGraph, DownloadedDependencyGraphNode, DownloadedGraph},
    manifest::DependencyType,
    refresh_sources,
    source::{
        traits::{PackageRef, PackageSource},
        PackageSources,
    },
    Project, PACKAGES_CONTAINER_NAME,
};
use fs_err::tokio as fs;
use std::{
    collections::HashSet,
    sync::{Arc, Mutex},
};

type MultithreadedGraph = Arc<Mutex<DownloadedGraph>>;

pub(crate) type MultithreadDownloadJob = (
    tokio::sync::mpsc::Receiver<Result<String, errors::DownloadGraphError>>,
    MultithreadedGraph,
);

impl Project {
    /// Downloads a graph of dependencies
    pub async fn download_graph(
        &self,
        graph: &DependencyGraph,
        refreshed_sources: &mut HashSet<PackageSources>,
        reqwest: &reqwest::Client,
        prod: bool,
        write: bool,
        wally: bool,
    ) -> Result<MultithreadDownloadJob, errors::DownloadGraphError> {
        let manifest = self.deser_manifest().await?;
        let manifest_target_kind = manifest.target.kind();
        let downloaded_graph: MultithreadedGraph = Arc::new(Mutex::new(Default::default()));

        let (tx, rx) = tokio::sync::mpsc::channel(
            graph
                .iter()
                .map(|(_, versions)| versions.len())
                .sum::<usize>()
                .max(1),
        );

        refresh_sources(
            self,
            graph
                .iter()
                .flat_map(|(_, versions)| versions.iter())
                .map(|(_, node)| node.pkg_ref.source()),
            refreshed_sources,
        )
        .await?;

        let project = Arc::new(self.clone());

        for (name, versions) in graph {
            for (version_id, node) in versions {
                // we need to download pesde packages first, since scripts (for target finding for example) can depend on them
                if node.pkg_ref.like_wally() != wally {
                    continue;
                }

                let tx = tx.clone();

                let name = name.clone();
                let version_id = version_id.clone();
                let node = node.clone();

                let project = project.clone();
                let reqwest = reqwest.clone();
                let downloaded_graph = downloaded_graph.clone();

                let package_dir = self.package_dir().to_path_buf();

                tokio::spawn(async move {
                    let source = node.pkg_ref.source();

                    let container_folder = node.container_folder(
                        &package_dir
                            .join(manifest_target_kind.packages_folder(version_id.target()))
                            .join(PACKAGES_CONTAINER_NAME),
                        &name,
                        version_id.version(),
                    );

                    match fs::create_dir_all(&container_folder).await {
                        Ok(_) => {}
                        Err(e) => {
                            tx.send(Err(errors::DownloadGraphError::Io(e)))
                                .await
                                .unwrap();
                            return;
                        }
                    }

                    let project = project.clone();

                    log::debug!("downloading {name}@{version_id}");

                    let (fs, target) =
                        match source.download(&node.pkg_ref, &project, &reqwest).await {
                            Ok(target) => target,
                            Err(e) => {
                                tx.send(Err(Box::new(e).into())).await.unwrap();
                                return;
                            }
                        };

                    log::debug!("downloaded {name}@{version_id}");

                    if write {
                        if !prod || node.resolved_ty != DependencyType::Dev {
                            match fs.write_to(container_folder, project.cas_dir(), true).await {
                                Ok(_) => {}
                                Err(e) => {
                                    tx.send(Err(errors::DownloadGraphError::WriteFailed(e)))
                                        .await
                                        .unwrap();
                                    return;
                                }
                            };
                        } else {
                            log::debug!("skipping writing {name}@{version_id} to disk, dev dependency in prod mode");
                        }
                    }

                    let display_name = format!("{name}@{version_id}");

                    {
                        let mut downloaded_graph = downloaded_graph.lock().unwrap();
                        downloaded_graph
                            .entry(name)
                            .or_default()
                            .insert(version_id, DownloadedDependencyGraphNode { node, target });
                    }

                    tx.send(Ok(display_name)).await.unwrap();
                });
            }
        }

        Ok((rx, downloaded_graph))
    }
}

/// Errors that can occur when downloading a graph
pub mod errors {
    use thiserror::Error;

    /// Errors that can occur when downloading a graph
    #[derive(Debug, Error)]
    #[non_exhaustive]
    pub enum DownloadGraphError {
        /// An error occurred deserializing the project manifest
        #[error("error deserializing project manifest")]
        ManifestDeserializationFailed(#[from] crate::errors::ManifestReadError),

        /// An error occurred refreshing a package source
        #[error("failed to refresh package source")]
        RefreshFailed(#[from] Box<crate::source::errors::RefreshError>),

        /// Error interacting with the filesystem
        #[error("error interacting with the filesystem")]
        Io(#[from] std::io::Error),

        /// Error downloading a package
        #[error("failed to download package")]
        DownloadFailed(#[from] Box<crate::source::errors::DownloadError>),

        /// Error writing package contents
        #[error("failed to write package contents")]
        WriteFailed(#[source] std::io::Error),
    }
}