use std::{fs::File, io::Write, path::PathBuf, process::exit, time::SystemTime};

use reqwest::StatusCode;
use sha2::{Digest, Sha512};

use crate::{
    check_command::{check_item, CheckResult},
    cli::{colors::{GREEN, RED, RESET}, DownloadArgs, DownloadExistingTreatment},
    lockfile::{load_project_printing, LockedFile3},
};

pub fn download_command(args: DownloadArgs) {
    let rt = tokio::runtime::Builder::new_current_thread()
        .enable_io()
        .enable_time()
        .build()
        .expect("Failed to build tokio runtime");

    rt.block_on(download_command_async(args));
}

async fn download_command_async(args: DownloadArgs) {
    let res = load_project_printing();

    for record in res.locked {
        handle_locked_file(record, args).await;
    }
}

async fn handle_locked_file(record: LockedFile3, args: DownloadArgs) {
    let check_res = check_item(&record);
    match check_res {
        CheckResult::Ok(_) => {
            println!("{GREEN}OK{RESET}:\t {}", &record.path);
        }
        CheckResult::Invalid(invalid_hash) => match args.existing_file_behavior {
            DownloadExistingTreatment::ValidateReplace => {
                println!(
                    "Downloading and replacing invalid file:\n\t{}",
                    &record.path
                );
                let _ = download_file(args, &record).await.unwrap();
                println!("Replaced invalid file:\n\t{}", &record.path);
            }
            DownloadExistingTreatment::ValidateFail => {
                println!("Existing file has an invalid hash:\n\t{}\n\texpected: {}\n\tfound: {invalid_hash} ;)", record.path, record.expected_hash);
            }
            DownloadExistingTreatment::ValidateReport => todo!(),
            DownloadExistingTreatment::Ignore => todo!(),
        },
        CheckResult::NotAFile => {
            println!("{RED}ERROR{RESET}:\tPath {} exists but is a directory.\nThis is unsupported at the moment", record.path);
        }
        CheckResult::Absent => {
            println!("Downloading absent file:\n\t{}", &record.path);
            match download_file(args, &record).await {
                Ok(_) => {
                    println!("Downloaded absent file:\n\t{}", &record.path);
                }
                Err(download_error) => handle_download_error(download_error, &record),
            }
        }
    }
}

fn handle_download_error(download_error: DownloadError, record: &LockedFile3) {
    match download_error {
        DownloadError::ErrorResponse(sc) => {
            println!(
                "Received an error HTTP status code ({sc}) upon downloading file: \n\t{}",
                record.path
            );
            exit(5);
        }
        DownloadError::HashMismatch {
            calculated,
            expected,
        } => {
            println!(
                "Downloaded file has a different hash:\n\tfile:{} \n\texpected: {}\n\treceived: {}",
                record.path, expected, calculated
            );
            exit(5);
        }
        DownloadError::IoError(err) => {
            println!(
                "An I/O error occurred while attempting to download a file: {}\n{err}",
                record.path
            );
        }
    }
}

async fn download_file(args: DownloadArgs, record: &LockedFile3) -> Result<String, DownloadError> {
    let mut res = reqwest::get(&record.url).await.unwrap();
    if res.status() != StatusCode::OK {
        return Err(DownloadError::ErrorResponse(res.status()));
    }
    let mut hasher = Sha512::new();

    let mut file = if args.direct_write {
        // TODO: Handle not-existent paths
        File::create(&record.path).unwrap()
    } else {
        todo!()
    };

    while let Some(chunk) = res.chunk().await.unwrap() {
        hasher.write_all(&chunk).unwrap();
        file.write_all(&chunk).unwrap();
    }

    let hash = hasher.finalize();
    let hash = format!("{hash:x}");
    if hash != record.expected_hash {
        return Err(DownloadError::HashMismatch {
            calculated: hash,
            expected: record.expected_hash.clone(),
        });
    }
    if let Err(err) = file.flush() {
        return Err(DownloadError::IoError(err));
    }

    Ok(hash)
}

/// TODO: not in use yet
fn get_temp_dir() -> PathBuf {
    let particle = SystemTime::now()
        .duration_since(SystemTime::UNIX_EPOCH)
        .unwrap_or_default()
        .as_millis();
    let particle = format!("{}-{particle}", env!("CARGO_BIN_NAME"));
    let mut path = std::env::temp_dir();
    path.push(particle);
    path
}

#[derive(Debug)]
enum DownloadError {
    ErrorResponse(StatusCode),
    HashMismatch {
        calculated: String,
        expected: String,
    },
    IoError(std::io::Error),
}