use std::cmp::min;
use std::error::Error;
use std::path::Path;

use crate::package_info;
use crate::package_info::PackageInfo;

use std::process::Command;

use log::debug;

use regex::Regex;

use crate::ProgressCallback;

fn clone_repo(
    url: &str,
    package: &str,
    branch: Option<&str>,
    cwd: Option<&Path>,
    progress: ProgressCallback<'_>,
) -> Result<(), Box<dyn Error>> {
    let target_path = if let Some(path) = cwd {
        path.join(package)
    } else {
        Path::new(package).to_path_buf()
    };

    let mut callbacks = git2::RemoteCallbacks::new();
    if let Some(ref progress_cb) = progress {
        // Download progress
        callbacks.transfer_progress(move |stats| {
            (progress_cb)(
                "",
                "Receiving objects...",
                stats.received_objects(),
                stats.total_objects(),
            );
            true
        });

        // Remote progress: messages 'Remote: compressing objects 10% (34/340)'
        // Parse progress informations to display them in callbacks
        callbacks.sideband_progress(move |data| {
            let msg = String::from_utf8_lossy(data);
            let re = Regex::new(r"(.*):[ ]*([0-9]*)% \(([0-9]*)/([0-9]*)\)").unwrap();
            if let Some(caps) = re.captures(msg.trim()) {
                let msg = caps.get(1).map_or("", |m| m.as_str()).to_string();
                let objects = caps
                    .get(3)
                    .map_or("", |m| m.as_str())
                    .to_string()
                    .parse::<usize>()
                    .unwrap_or(0);
                let total = caps
                    .get(4)
                    .map_or("", |m| m.as_str())
                    .to_string()
                    .parse::<usize>()
                    .unwrap_or(0);

                (progress_cb)("", msg.as_str(), objects, total);
            }

            true
        });
    }

    let mut fetch_options = git2::FetchOptions::new();
    fetch_options.remote_callbacks(callbacks);

    let mut builder = git2::build::RepoBuilder::new();
    builder.fetch_options(fetch_options);

    if let Some(b) = branch {
        builder.branch(b);
    }

    match builder.clone(url, &target_path) {
        Ok(_repo) => Ok(()),
        Err(e) => Err(format!("Failed to clone: {}", e).into()),
    }
}

use sha2::{Digest, Sha256};
use std::fs::File;
use std::io::Write;

use flate2::read::GzDecoder;
use futures_util::StreamExt;
use tar::Archive;
use xz2::read::XzDecoder;

fn extract_archive(path: &Path, dest: &Path) -> Result<(), Box<dyn Error>> {
    let file = File::open(path)?;
    let filename = path.file_name().unwrap().to_string_lossy();

    if filename.ends_with(".tar.gz") || filename.ends_with(".tgz") {
        let tar = GzDecoder::new(file);
        let mut archive = Archive::new(tar);
        archive.unpack(dest)?;
    } else if filename.ends_with(".tar.xz") || filename.ends_with(".txz") {
        let tar = XzDecoder::new(file);
        let mut archive = Archive::new(tar);
        archive.unpack(dest)?;
    } else {
        return Err(format!("Unsupported archive format: {}", filename).into());
    }

    Ok(())
}

fn checkout_pristine_tar(package_dir: &Path, filename: &str) -> Result<(), Box<dyn Error>> {
    let output = Command::new("pristine-tar")
        .current_dir(package_dir)
        .args(["checkout", format!("../{filename}").as_str()])
        .output()
        .expect("pristine-tar checkout failed");

    if !output.status.success() {
        return Err(format!(
            "pristine-tar checkout failed with status: {}",
            output.status
        )
        .into());
    }
    Ok(())
}

async fn download_file_checksum(
    url: &str,
    checksum: &str,
    target_dir: &Path,
    progress: ProgressCallback<'_>,
) -> Result<(), Box<dyn Error>> {
    // Download with reqwest
    let response = reqwest::get(url).await?;
    if !response.status().is_success() {
        return Err(format!("Failed to download '{}' : {}", &url, response.status()).into());
    }

    let total_size = response
        .content_length()
        .ok_or(format!("Failed to get content length from '{}'", &url))?;
    let mut index = 0;

    // Target file: extract file name from URL
    let filename = Path::new(url).file_name().unwrap().to_str().unwrap();
    let path = target_dir.join(filename);
    let mut file = File::create(path)?;

    // Download chunk by chunk to disk, while updating hasher for checksum
    let mut stream = response.bytes_stream();
    let mut hasher = Sha256::new();
    while let Some(item) = stream.next().await {
        let chunk = item?;
        file.write_all(&chunk)?;
        hasher.update(&chunk);

        if let Some(cb) = progress {
            index = min(index + chunk.len(), total_size as usize);
            cb("", "Downloading...", index, total_size as usize);
        }
    }

    // Verify checksum
    let result = hasher.finalize();
    let calculated_checksum = hex::encode(result);
    if calculated_checksum != checksum {
        return Err(format!(
            "Checksum mismatch! Expected {}, got {}",
            checksum, calculated_checksum
        )
        .into());
    }

    Ok(())
}

fn setup_pristine_tar_branch(package_dir: &Path, dist: &str) -> Result<(), Box<dyn Error>> {
    let repo = git2::Repository::open(package_dir)?;

    // Check if local branch already exists
    if repo
        .find_branch("pristine-tar", git2::BranchType::Local)
        .is_ok()
    {
        return Ok(());
    }

    // Find remote pristine-tar branch
    let branches = repo.branches(Some(git2::BranchType::Remote))?;
    for branch_result in branches {
        let (branch, _) = branch_result?;
        if let Some(name) = branch.name()?
            && name.ends_with(&format!("/{dist}/pristine-tar"))
        {
            debug!("Found remote pristine-tar branch: {}", name);

            let commit = branch.get().peel_to_commit()?;

            // Create local branch
            let mut local_branch = repo.branch("pristine-tar", &commit, false)?;

            // Set upstream
            local_branch.set_upstream(Some(name))?;

            debug!("Created local pristine-tar branch tracking {}", name);
            return Ok(());
        }
    }

    debug!("No remote pristine-tar branch found.");
    Ok(())
}

async fn fetch_orig_tarball(
    info: &PackageInfo,
    cwd: Option<&Path>,
    progress: ProgressCallback<'_>,
) -> Result<(), Box<dyn Error>> {
    let package_dir = if let Some(path) = cwd {
        path.join(&info.stanza.package)
    } else {
        Path::new(&info.stanza.package).to_path_buf()
    };

    // Find the orig tarball in the file list
    // Usually ends with .orig.tar.gz or .orig.tar.xz
    let orig_file = info
        .stanza
        .files
        .iter()
        .find(|f| f.name.contains(".orig.tar."))
        .unwrap();
    let filename = &orig_file.name;

    // 1. Try executing pristine-tar

    // Setup pristine-tar branch if needed (by tracking remote branch)
    let _ = setup_pristine_tar_branch(&package_dir, info.dist.as_str());

    if let Err(e) = checkout_pristine_tar(&package_dir, filename.as_str()) {
        debug!(
            "pristine-tar failed: {}. Falling back to archive download.",
            e
        );

        // 2. Fallback to archive download
        // We download to the parent directory of the package repo (which is standard for build tools)
        // or the current directory if cwd is None (which effectively is the parent of the package dir)
        let target_dir = cwd.unwrap_or_else(|| Path::new("."));
        download_file_checksum(
            format!("{}/{}", &info.archive_url, filename).as_str(),
            &orig_file.sha256,
            target_dir,
            progress,
        )
        .await?;
    }

    Ok(())
}

async fn fetch_archive_sources(
    info: &PackageInfo,
    cwd: Option<&Path>,
    progress: ProgressCallback<'_>,
) -> Result<(), Box<dyn Error>> {
    let package_dir = if let Some(path) = cwd {
        path.join(&info.stanza.package)
    } else {
        Path::new(&info.stanza.package).to_path_buf()
    };

    std::fs::create_dir_all(&package_dir)?;

    for file in &info.stanza.files {
        let url = format!("{}/{}", info.archive_url, file.name);
        download_file_checksum(&url, &file.sha256, &package_dir, progress).await?;
    }

    // Extract the debian tarball or diff
    let debian_file = info
        .stanza
        .files
        .iter()
        .find(|f| f.name.contains(".debian.tar.") || f.name.contains(".diff.gz"));

    if let Some(file) = debian_file {
        let path = package_dir.join(&file.name);
        let extract_dir = package_dir.join(&info.stanza.package);

        if (file.name.ends_with(".tar.xz") || file.name.ends_with(".tar.gz"))
            && let Err(e) = extract_archive(&path, &extract_dir)
        {
            return Err(format!("Failed to extract {}: {}", file.name, e).into());
        }

        // Remove archive after extraction
        std::fs::remove_file(&path)?;
    }

    Ok(())
}

pub async fn pull(
    package: &str,
    _version: &str,
    series: Option<&str>,
    pocket: &str,
    _ppa: &str,
    dist: Option<&str>,
    cwd: Option<&Path>,
    progress: ProgressCallback<'_>,
) -> Result<PackageInfo, Box<dyn Error>> {
    let version_opt = if _version.is_empty() {
        None
    } else {
        Some(_version)
    };

    /* Obtain the package information, either directly in a series or with a search in all series */
    let package_info = if let Some(s) = series {
        if let Some(cb) = progress {
            cb(
                &format!("Resolving package info for {}...", package),
                "",
                0,
                0,
            );
        }

        // Get the package information from that series and pocket
        package_info::get(package, s, pocket, version_opt).await?
    } else {
        let dist = dist.unwrap_or_else(||
            // Use auto-detection to see if current distro is ubuntu, or fallback to debian by default
            if std::process::Command::new("lsb_release").arg("-i").arg("-s").output()
                .map(|o| String::from_utf8_lossy(&o.stdout).trim().to_lowercase()).unwrap_or_default() == "ubuntu" {
                "ubuntu"
            } else {
                "debian"
            }
        );

        if let Some(cb) = progress {
            cb(
                &format!("Searching for package {} in {}...", package, dist),
                "",
                0,
                0,
            );
        }

        // Try to find the package in all series from that dist
        package_info::find_package(package, dist, pocket, version_opt, progress).await?
    };

    let package_dir = if let Some(path) = cwd {
        path.join(package)
    } else {
        Path::new(package).to_path_buf()
    };

    /* Fetch the package: either via git (preferred VCS) or the archive */
    if let Some(ref url) = package_info.preferred_vcs {
        // We have found a preferred VCS (git repository) for the package, so
        // we fetch the package from that repo.

        // Depending on target series, we pick target branch; if no series is specified,
        // we target the development branch, i.e. the default branch
        let branch_name = if let Some(s) = series {
            if package_info.dist == "ubuntu" {
                Some(format!("{}/{}", package_info.dist, s))
            } else {
                // Debian does not have reliable branch naming...
                // For now, we skip that part and clone default
                // TODO: Inspect remote branches and tags for matches
                None
            }
        } else {
            None
        };

        if let Some(cb) = progress {
            cb(
                &format!(
                    "Cloning {}{}...",
                    url,
                    if let Some(b) = &branch_name {
                        format!(" (branch {})", b)
                    } else {
                        String::new()
                    }
                ),
                "",
                0,
                0,
            );
        }
        clone_repo(
            url.as_str(),
            package,
            branch_name.as_deref(),
            Some(&package_dir),
            progress,
        )?;
        if !package_info.is_native() {
            if let Some(cb) = progress {
                cb("Fetching orig tarball...", "", 0, 0);
            }
            fetch_orig_tarball(&package_info, Some(&package_dir), progress).await?;
        } else {
            debug!("Native package, skipping orig tarball fetch.");
        }
    } else {
        // Fallback to archive fetching
        if let Some(cb) = progress {
            cb("Downloading from archive...", "", 0, 0);
        }
        fetch_archive_sources(&package_info, Some(cwd.unwrap_or(Path::new("."))), progress).await?;
    }

    Ok(package_info)
}

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

    async fn test_pull_package_end_to_end(package: &str, series: Option<&str>, dist: Option<&str>) {
        // This test verifies that 'pkh pull' clones the repo and fetches the tarball.

        // For determinism, we require for tests that either a distro or series is specified,
        // as no distribution would mean fallback to system distro
        assert!(dist != None || series != None);

        // Use a temp directory as working directory
        let temp_dir = tempfile::tempdir().unwrap();
        let cwd = temp_dir.path();

        // Main 'pull' command: the one we want to test
        let info = pull(package, "", series, "", "", dist, Some(cwd), None)
            .await
            .unwrap();

        let package_dir = cwd.join(package);
        assert!(package_dir.exists());
        let package_source_dir = package_dir.join(package);
        assert!(
            package_source_dir.exists(),
            "Package git repo directory not created"
        );
        assert!(
            package_source_dir.join("debian").exists(),
            "debian directory not present"
        );

        if package_source_dir.join(".git").exists() {
            // Verify we are on the correct branch
            let repo = git2::Repository::open(&package_source_dir).unwrap();
            let head = repo.head().unwrap();
            let name = head.name().unwrap();

            if let Some(s) = series {
                // The local branch should be named dist/series
                // We skip debian for now as it does not have a reliable naming scheme
                if info.dist == "ubuntu" {
                    assert_eq!(name, format!("refs/heads/{0}/{s}", info.dist));
                }
            } else {
                // The local branch should be named ubuntu/devel for Ubuntu
                // Debian unfortunately does not have a reliable naming scheme
                // Given that there was no series specified, and this is a test,
                // we require to have a distribution specified
                if dist.unwrap() == "ubuntu" {
                    assert_eq!(name, "refs/heads/ubuntu/devel");
                }
            }
        }

        // Check for orig tarball in package dir
        let mut found_tarball = false;
        for entry in std::fs::read_dir(package_dir).unwrap() {
            let entry = entry.unwrap();
            let name = entry.file_name().to_string_lossy().to_string();
            if name.contains(".orig.tar.") {
                found_tarball = true;
                break;
            }
        }

        assert!(found_tarball, "Orig tarball not found in package dir");
    }

    #[tokio::test]
    async fn test_pull_hello_ubuntu_end_to_end() {
        test_pull_package_end_to_end("hello", Some("noble"), None).await;
    }
    #[tokio::test]
    async fn test_pull_hello_debian_end_to_end() {
        test_pull_package_end_to_end("hello", Some("bookworm"), None).await;
    }

    #[tokio::test]
    async fn test_pull_2048_universe_ubuntu_end_to_end() {
        test_pull_package_end_to_end("2048", Some("noble"), None).await;
    }
    #[tokio::test]
    async fn test_pull_1oom_contrib_debian_end_to_end() {
        test_pull_package_end_to_end("1oom", Some("trixie"), None).await;
    }

    #[tokio::test]
    async fn test_pull_agg_svn_fallback_ok() {
        test_pull_package_end_to_end("agg", Some("trixie"), None).await;
    }

    #[tokio::test]
    async fn test_pull_hello_debian_latest_end_to_end() {
        test_pull_package_end_to_end("hello", None, Some("debian")).await;
    }
    #[tokio::test]
    async fn test_pull_hello_ubuntu_latest_end_to_end() {
        test_pull_package_end_to_end("hello", None, Some("ubuntu")).await;
    }
}