use std::{io::{Stdin, IsTerminal}, process::{exit, Command, Stdio}};


struct Config {
    ssh_destination: String,
    xochitl_path: String,
    ssh_key_path: Option<String>,
    extensions: Extensions
}

#[derive(Default, Clone)]
struct Extensions {
    unavailable_response: bool,
    info: bool
}

fn get_line(stdin: &mut Stdin) -> Option<String> {
    let mut buf = String::new();
    match stdin.read_line(&mut buf) {
        Ok(0) => None,
        Err(err) => {
            eprintln!("read encountered error: {}", err);
            None
        }
        _ => Some(buf)
    }
}

fn get_value(stdin: &mut Stdin) -> Option<String> {
    if let Some(line) = get_line(stdin) {
        if let Some(value) = line.strip_prefix("VALUE ") {
            if value.split_ascii_whitespace().count() == 0 {
                return None
            } else {
                return Some(value.to_owned());
            }
        }
        if line == "VALUE" {
            return None;
        }
    }
    eprintln!("did not receive value when expected");
    exit(1);
}

fn get_config_value(stdin: &mut Stdin, key: &str) -> Option<String> {
    println!("GETCONFIG {}", key);
    get_value(stdin)
}

fn get_config(stdin: &mut Stdin, extensions: &Extensions) -> Config {
    Config {
        ssh_destination: get_config_value(stdin, "ssh_destination").unwrap()
            .strip_suffix("\n").unwrap().to_string(),
        xochitl_path: get_config_value(stdin, "xochitl_directory")
            .map(|s| s.strip_suffix("\n").unwrap().to_string())
            .unwrap_or_else(|| ".local/share/remarkable/xochitl".to_owned()),
        ssh_key_path: get_config_value(stdin, "ssh_key"),
        extensions: extensions.to_owned()
    }
}

fn startup(stdin: &mut Stdin) -> Config {
    let mut extensions = Extensions::default();
    while let Some(line) = get_line(stdin) {
        let mut words = line.split_ascii_whitespace();
        let verb = words.next().expect("missing command verb");
        match verb {
            "EXTENSIONS" => {
                let supported: Vec<_> = words.collect();
                extensions.unavailable_response = supported.contains(&"UNAVAILABLERESPONSE");
                extensions.info = supported.contains(&"INFO");
                println!(
                    "EXTENSIONS {} {}",
                    if extensions.unavailable_response { "UNAVAILABLERESPONSE" } else { "" },
                    if extensions.info { "INFO" } else { "" }
                )
            }
            "PREPARE" => {
                let config = get_config(stdin, &extensions);
                println!("PREPARE-SUCCESS");
                return config;
            },
            "LISTCONFIGS" => {
                println!("CONFIG ssh_destination ssh destination under which the reMarkable tablet can be reached.");
                println!("CONFIG ssh_key the path to an ssh key to use (optional).");
                println!("CONFIG xochitl_directory the directory on the remarkable device in which data is stored (default .local/share/remarkable/xochitl).");
                println!("CONFIGEND")
            },
            "INITREMOTE" => {
                let config = get_config(stdin, &extensions);
                let check = Command::new("ssh")
                    .arg(config.ssh_destination)
                    .arg("ls")
                    .arg(config.xochitl_path)
                    .stdout(Stdio::null())
                    .status();
                if let Ok(status) = check {
                    if status.success() {
                        println!("INITREMOTE-SUCCESS");
                    } else {
                        println!("INITREMOTE-FAILURE ssh check returned {}", status);
                    }
                } else {
                    println!("INITREMOTE-FAILURE failed to spawn ssh check command");
                }
            }
            _ => {
                println!("UNSUPPORTED-REQUEST");
                eprintln!("got unsupported verb while getting config: {}", line);
            }
        }
    }
    println!("DEBUG done early?");
    exit(0);
}


fn key_to_uuid(key: &str) -> String {
    let maybe = Command::new("uuidgen")
        .arg("-s")
        .arg("-n")
        .arg("435bb27b-6704-416f-bc5b-3e2d02d0cf8f")
        .arg("-N")
        .arg(key)
        .output();
    match maybe {
        Ok(uuid) => String::from_utf8_lossy(&uuid.stdout)
            .split_ascii_whitespace().next().unwrap().to_owned(),
        Err(e) => {
            println!("DEBUG conversion to uuid failed: {}", e);
            exit(1)
        }
    }
}

fn check_key_present<'a>(config: &Config, mut words: impl Iterator<Item=&'a str>) {
    let key = words.next().unwrap();
    assert_no_args_left(words);
    let uuid = key_to_uuid(key);
    let check = Command::new("ssh")
        .arg(&config.ssh_destination)
        .arg(format!("test -f {dir}/{uuid}.pdf && test ! -f {dir}/{uuid}.tombstone", dir=config.xochitl_path, uuid=uuid))
        .status();
    if let Ok(code) = check {
        if code.success() {
            println!("CHECKPRESENT-SUCCESS {}", key);
        } else {
            println!("CHECKPRESENT-FAILURE {}", key); // TODO: check if remote present or not
        }
    } else {
        println!("CHECKPRESENT-UNKNOWN {} ssh failed", key);
    }
}

fn store_key<'a>(config: &Config, mut words: impl Iterator<Item=&'a str>) {
    let key = words.next().unwrap();
    let file = words.next().unwrap();
    assert_no_args_left(words);
    let uuid = key_to_uuid(key);
    let check = Command::new("scp")
        .arg(file)
        .arg(format!("{}:{}/{}.pdf", config.ssh_destination, config.xochitl_path, uuid))
        .status();
    if let Ok(code) = check {
        if code.success() {
            println!("TRANSFER-SUCCESS STORE {}", key);
        } else {
            println!("TRANSFER-FAILURE STORE {}", key); // TODO: check if remote present or not
        }
    } else {
        println!("TRANSFER-FAILURE STORE {} ssh failed", key);
    }
}

fn retrieve_key<'a>(config: &Config, mut words: impl Iterator<Item=&'a str>) {
    let key = words.next().unwrap();
    let file = words.next().unwrap();
    assert_no_args_left(words);
    let uuid = key_to_uuid(key);
    let check = Command::new("scp")
        .arg(format!("{}:{}/{}.pdf", config.ssh_destination, config.xochitl_path, uuid))
        .arg(file)
        .status();
    if let Ok(code) = check {
        if code.success() {
            println!("TRANSFER-SUCCESS RETRIEVE {}", key);
        } else {
            println!("TRANSFER-FAILURE RETRIEVE {}", key); // TODO: check if remote present or not
        }
    } else {
        println!("TRANSFER-FAILURE RETRIEVE {} ssh failed", key);
    }
}

fn remove_key<'a>(config: &Config, mut words: impl Iterator<Item=&'a str>) {
    let key = words.next().unwrap();
    assert_no_args_left(words);
    let uuid = key_to_uuid(key);

    let cmd = Command::new("ssh")
        .arg(&config.ssh_destination)
        .arg(format!("rm -r {dir}/{uuid}*", dir=config.xochitl_path, uuid=uuid))
        .status();
    if let Ok(code) = cmd {
        if code.success() {
            println!("REMOVE-SUCCESS {}", key);
        } else {
            println!("REMOVE-FAILURE {} command failed", key); // TODO: check if remote present or not
        }
    } else {
        println!("REMOVE-FAILURE {} ssh failed", key);
    }
}

fn whereis<'a>(config: &Config, mut words: impl Iterator<Item=&'a str>) {
    let key = words.next().unwrap();
    assert_no_args_left(words);
    let uuid = key_to_uuid(key);
    println!("WHEREIS-SUCCESS {ssh}:{dir}/{uuid}.pdf", ssh=config.ssh_destination, dir=config.xochitl_path, uuid=uuid);
}

fn assert_no_args_left<'a>(mut words: impl Iterator<Item=&'a str>) {
    if words.next().is_some() {
        println!("UNSUPPORTED-REQUEST");
        println!("ERROR");
        exit(1);
    }
}

fn main() {
    let mut stdin = std::io::stdin();
    if stdin.is_terminal() {
        eprintln!("warning: this program is not meant to be invoked by hand.");
    }

    println!("VERSION 2");

    let config = startup(&mut stdin);

    while let Some(line) = get_line(&mut stdin) {
        let mut words = line.split_ascii_whitespace();
        let verb = words.next().expect("missing command verb");
        match verb {
            "CHECKPRESENT" => check_key_present(&config, words),
            "TRANSFER" => match words.next().expect("missing STORE/RETRIEVE") {
                "STORE" => store_key(&config, words),
                "RETRIEVE" => retrieve_key(&config, words),
                _ => println!("UNSUPPORTED-REQUEST")
            }
            "REMOVE" => remove_key(&config, words),
            "WHEREIS" => whereis(&config, words),
            "GETAVAILABILITY" => {
                println!("ERROR");
                unimplemented!()
                // check routing table if usb network device is present?
            }
            _ => println!("UNSUPPORTED-REQUEST")
        }
    }

}