use std::{
    borrow::Cow,
    ffi::{CStr, CString},
    fs::File,
    path::{Path, PathBuf},
    sync::LazyLock,
    time::{Duration, SystemTime},
};

use anyhow::Context as _;
use dialoguer::theme::Theme as _;
use gpgme::Context;
use tracing::{error, info, warn};

use crate::cli::{STDERR, THEME};

pub fn main(_global_cli: crate::cli::GlobalArgs, cli: crate::cli::ImportCli) -> anyhow::Result<()> {
    let mut ctx = gpgme::Context::from_protocol(gpgme::Protocol::OpenPgp)?;

    let key = select_key(&mut ctx, cli.patterns.iter().map(Cow::as_ref))?;

    let fingerprint = key
        .fingerprint_raw()
        .context("querying the fingerprint of your key")?
        .to_str()
        .expect("this should always be valid UTF-8");

    let alias = dialoguer::Input::<String>::with_theme(&*THEME)
        .with_prompt("What should this identity be named?")
        .interact_text()?;

    let authkey: Option<PathBuf> = select_authkey(&mut ctx, &key, &alias)?;

    let (name, email) = select_name_and_email(&key)?;

    let identity = crate::data::Identity {
        alias,
        data: crate::data::IdentityData {
            name,
            email,
            sigkey: Some(fingerprint.to_owned()),
            authkey,
        },
    };

    info!("Imported identity {identity}");

    identity.save_interactively()?;

    Ok(())
}

fn select_key<P>(ctx: &mut gpgme::Context, patterns: P) -> anyhow::Result<gpgme::Key>
where
    P: IntoIterator,
    Vec<u8>: From<<P as IntoIterator>::Item>,
{
    let patterns: Vec<CString> = patterns
        .into_iter()
        .map(|p| Ok(CString::new(p)?))
        .collect::<anyhow::Result<_>>()
        .context("Converting patterns to CStrings")?;

    let mut keys = ctx
        .find_secret_keys(patterns.iter())?
        .inspect(|it| {
            if let Err(err) = it {
                error!("failed to query information about a key. Got err: {err}");
            }
        })
        .filter_map(Result::ok)
        .collect::<Vec<gpgme::Key>>();

    match keys.len() {
        0 => {
            STDERR.write_line("Found no matching key")?;
            std::process::exit(1);
        }
        1 => return Ok(keys.pop().expect("Vec is non empty")),
        _ => (),
    }

    // There is some weird behavior when using FuzzySelect with items spanning multiple lines
    STDERR.clear_screen()?;

    let index = dialoguer::FuzzySelect::with_theme(&*THEME)
        .with_prompt("Select a GPG key to import")
        .items(keys.iter().map(format_key_for_select))
        .highlight_matches(false)
        .interact()?;

    Ok(keys.swap_remove(index))
}

fn format_key_for_select(key: &gpgme::Key) -> Cow<'static, str> {
    let fingerprint: Cow<str> = key
        .fingerprint_raw()
        .map(CStr::to_string_lossy)
        .unwrap_or(Cow::Borrowed(&FINGERPRINT_ERRSTR));

    let primary_key: Cow<str> = key
        .primary_key()
        .and_then(|key| format_subkey(key, true))
        .unwrap_or(Cow::Borrowed(&PRIMARY_KEY_ERRSTR));

    let user_ids: String = itertools::intersperse(
        key.user_ids()
            .map(|uid| Cow::Owned(format!("  uid           {}", format_user_id(&uid)))),
        Cow::Borrowed("\n"),
    )
    .collect();

    let subkeys = itertools::intersperse(
        key.subkeys().map(|key| {
            Cow::Owned(format!(
                "  {}",
                format_subkey(key, false).unwrap_or(Cow::Borrowed(&SUBKEY_ERRSTR))
            ))
        }),
        Cow::Borrowed("\n"),
    )
    .collect::<String>();

    let formatted = format!("{primary_key}\n        {fingerprint:40}\n{user_ids}\n{subkeys}\n");

    Cow::Owned(formatted)
}

fn format_subkey(key: gpgme::Subkey, is_primary: bool) -> Option<Cow<'static, str>> {
    let algorithm = key
        .algorithm()
        .name_raw()
        .map(CStr::to_string_lossy)
        .unwrap_or(Cow::Borrowed(&ALGORITHM_ERRSTR));

    let creation_time: Cow<str> = key
        .creation_time()
        .map(|time| {
            let creation_time = chrono::DateTime::UNIX_EPOCH
                + time
                    .duration_since(SystemTime::UNIX_EPOCH)
                    .unwrap_or(Duration::ZERO);

            let local_creation_time = creation_time.with_timezone(&chrono::Local::now().timezone());

            let formatted = local_creation_time.format("%Y-%m-%d").to_string();

            Cow::Owned(formatted)
        })
        .unwrap_or(Cow::Borrowed(&CREATION_TIME_ERRSTR));

    let capabilities = {
        let mut caps = String::new();

        if key.can_sign() {
            caps.push('S');
        }
        if key.can_encrypt() {
            caps.push('E')
        }
        if key.can_certify() {
            caps.push('C');
        }
        if key.can_authenticate() {
            caps.push('A');
        }

        caps
    };

    let formatted = format!(
        "{:3}   {algorithm:7} {creation_time} [{capabilities}]",
        match (key.is_secret(), is_primary) {
            (true, true) => "sec",
            (false, true) => "pub",
            (true, false) => "ssb",
            (false, false) => "syb",
        },
    );

    Some(Cow::Owned(formatted))
}

fn format_user_id(uid: &gpgme::UserId) -> String {
    let [name, comment, email] = [uid.name_raw(), uid.comment_raw(), uid.email_raw()]
        .map(|attr| attr.map(CStr::to_string_lossy).unwrap_or(Cow::Borrowed("")));

    format!("{name} ({comment}) <{email}>")
}

macro_rules! format_error_strings {
    ($($name:ident = $val:expr;)+) => {
        $(
            static $name: LazyLock<String> = LazyLock::new(|| {
                let mut out = String::new();
                THEME
                    .format_error(&mut out, $val)
                    .expect("format failed");
                out
            });
        )*
    }
}

format_error_strings! {
    PRIMARY_KEY_ERRSTR = "[failed to query primary key]";
    SUBKEY_ERRSTR = "[failed to query subkey]";
    FINGERPRINT_ERRSTR = "[failed to query fingerprint]";
    ALGORITHM_ERRSTR = "[failed to query algorithm]";
    CREATION_TIME_ERRSTR = "[failed to query creation time]";
}

fn select_authkey(
    ctx: &mut gpgme::Context,
    key: &gpgme::Key,
    identity_name: &str,
) -> anyhow::Result<Option<PathBuf>> {
    let mut authkey_prompt = dialoguer::Input::<String>::with_theme(&*THEME)
        .with_prompt("Select an SSH key (leave empty for none)")
        .validate_with(|input: &String| -> Result<(), Cow<str>> {
            if input.is_empty() {
                return Ok(());
            }

            match std::fs::exists(input) {
                Ok(true) => Ok(()),
                Ok(false) => Err(Cow::Borrowed("file not found")),
                Err(err) => Err(Cow::Owned(err.to_string())),
            }
        })
        .allow_empty(true);

    if let Some(authkey) = try_export_as_ssh_key(ctx, key, identity_name)? {
        let default_authkey = authkey.to_string_lossy();

        if default_authkey.contains(char::REPLACEMENT_CHARACTER) {
            warn!(
                "the path to the key you just imported contains non UTF-8 characters. They will be lost if you enter it as is"
            );
        }

        authkey_prompt = authkey_prompt.with_initial_text(default_authkey);
    }

    let authkey = authkey_prompt.interact_text()?;

    Ok(if authkey.is_empty() {
        None
    } else {
        Some(PathBuf::from(authkey))
    })
}

/// Checks if the key has authentication capabilities then handles exporting is as an SSH key
/// according to the user's input.
fn try_export_as_ssh_key(
    ctx: &mut gpgme::Context,
    key: &gpgme::Key,
    identity_name: &str,
) -> anyhow::Result<Option<PathBuf>> {
    if !key.can_authenticate()
        || !dialoguer::Confirm::with_theme(&*THEME)
            .with_prompt(
                "This key can authenticate. Do you want to export it as an SSH key for later?",
            )
            .interact()?
    {
        return Ok(None);
    }

    let default_destination = {
        let mut path = crate::data::DATA_FOLDER.clone();
        path.push("ssh");
        path.push(format!("{identity_name}.pub"));
        path
    };

    let destination: PathBuf = dialoguer::Input::<String>::with_theme(&*THEME)
        .with_prompt("Save as")
        // FIXME: we are screwed if for example the linux user's name contains non valid UTF-8
        .with_initial_text(default_destination.to_string_lossy())
        .interact_text()?
        .into();

    let fingerprint = key
        .fingerprint_raw()
        .context("querying your key's fingerprint")?;

    save_ssh_key(ctx, fingerprint, &destination)?;

    info!("succesfully saved your SSH key to disk");

    Ok(Some(destination))
}

fn save_ssh_key<P: AsRef<Path>>(
    ctx: &mut Context,
    fingerprint: &CStr,
    path: P,
) -> anyhow::Result<()> {
    if std::fs::exists(&path).context("Checking if file already exists")?
        && !dialoguer::Confirm::with_theme(&*THEME)
            .with_prompt(format!(
                "{} already exists. Overwrite?",
                path.as_ref().display()
            ))
            .interact()?
    {
        return Ok(());
    }

    let parent = {
        let mut path = PathBuf::from(path.as_ref());
        path.pop();
        path
    };
    std::fs::create_dir_all(parent).context("Creating parent directories")?;

    let mut out = File::options()
        .create(true)
        .write(true)
        .truncate(true)
        .append(false)
        .open(&path)?;

    ctx.export([fingerprint], gpgme::ExportMode::SSH, &mut out)
        .context("asking GPG to export your SSH key")?;

    Ok(())
}

fn select_name_and_email(key: &gpgme::Key) -> anyhow::Result<(Option<String>, Option<String>)> {
    fn select<'key, G>(
        key: &'key gpgme::Key,
        item_kind: &str,
        getter: G,
    ) -> anyhow::Result<Option<String>>
    where
        G: Fn(&gpgme::UserId<'key>) -> Option<&'key CStr>,
    {
        let mut items_and_uids = key
            .user_ids()
            .flat_map(|uid| Some((getter(&uid)?, format_user_id(&uid))))
            .collect::<Vec<(&CStr, String)>>();

        let picked: Option<String> = if items_and_uids.is_empty() {
            None
        } else {
            let choice = dialoguer::FuzzySelect::with_theme(&*THEME)
                .with_prompt(format!(
                    "From which user ID would you like to import your {item_kind}?"
                ))
                .items(
                    std::iter::once("None (enter my own or leave empty)")
                        .chain(items_and_uids.iter().map(|pair| pair.1.as_str())),
                )
                .interact()?;

            if choice == 0 {
                None
            } else {
                let out = items_and_uids.swap_remove(choice - 1).0;
                drop(items_and_uids);
                Some(out.to_string_lossy().to_string())
            }
        };

        let result = if let Some(item) = picked {
            Some(item)
        } else {
            let input = dialoguer::Input::<String>::with_theme(&*THEME)
                .with_prompt(format!("Enter your {item_kind} (leave empty for none)"))
                .allow_empty(true)
                .interact_text()?;

            if input.is_empty() { None } else { Some(input) }
        };

        Ok(result)
    }

    let name = select(key, "name", gpgme::UserId::name_raw)?;
    let email = select(key, "email", gpgme::UserId::email_raw)?;

    Ok((name, email))
}