use std::{
    fmt::Display,
    io::{self, Write},
    path::Path,
    str::FromStr,
};

use anyhow::{anyhow, bail, Context, Result};
use clap::{crate_version, App, Arg, ArgMatches, SubCommand};
use itertools::Itertools;
use log::debug;
use termcolor::{Color, ColorChoice, ColorSpec, StandardStream, WriteColor};

use modderbaas::{
    minemod::ModContainer, util, Baas, ContentDb, Downloader, MineMod, Snapshot, Source, World,
};

fn main() -> Result<()> {
    stderrlog::new()
        .module(module_path!())
        //.verbosity(1)
        .verbosity(5)
        .init()
        .unwrap();

    let matches = App::new("ModderBaas")
        .version(crate_version!())
        .arg(
            Arg::with_name("world")
                .long("world")
                .short("c")
                .required(false)
                .help("Select the world that we should operate on")
                .takes_value(true),
        )
        .subcommand(
            SubCommand::with_name("enable")
                .about("Enables a mod and its dependencies")
                .arg(
                    Arg::with_name("mod")
                        .multiple(true)
                        .required(true)
                        .help("The mod to enable"),
                ),
        )
        .subcommand(
            SubCommand::with_name("install")
                .about("Installs a mod and its dependencies")
                .arg(
                    Arg::with_name("mod")
                        .multiple(true)
                        .required(true)
                        .help("The mod to install"),
                )
                .arg(
                    Arg::with_name("target")
                        .short("t")
                        .long("target-dir")
                        .help("The mod target directory")
                        .default_value("."),
                )
                .arg(
                    Arg::with_name("dry-run")
                        .short("n")
                        .long("dry-run")
                        .help("Only resolve dependencies, don't actually install any mods")
                        .required(false),
                )
                .arg(
                    Arg::with_name("fix-permissions")
                        .short("p")
                        .long("fix-permissions")
                        .help("Change the owner of the installed mod to match target-dir's")
                        .required(false),
                ),
        )
        .get_matches();

    let mut stdout = StandardStream::stdout(ColorChoice::Auto);

    let baas = Baas::with_standard_dirs()?;
    let snapshot = baas
        .snapshot()
        .context("Creating the initial snapshot failed")?;

    let world = select_world(&mut stdout, &matches, &snapshot)?;
    write!(stdout, "Using world ")?;
    stdout.set_color(ColorSpec::new().set_fg(Some(Color::Green)))?;
    writeln!(stdout, "{}", world.world_name()?)?;
    stdout.reset()?;

    if let Some(enable) = matches.subcommand_matches("enable") {
        let mods = enable.values_of("mod").unwrap().collect::<Vec<_>>();
        enable_mods(&mut stdout, &snapshot, &world, &mods)?;
    }

    if let Some(install) = matches.subcommand_matches("install") {
        let mods = install.values_of("mod").unwrap().collect::<Vec<_>>();
        install_mods(&mut stdout, &snapshot, &world, &mods, install)?;
    }

    Ok(())
}

/// Select the world that we want to work on.
///
/// If there is only one world available, we use it.
/// If there are more worlds, we ask the user for a choice.
///
/// If the command line argument is given, it overrides the previous rules.
fn select_world(
    output: &mut StandardStream,
    cli: &ArgMatches,
    snapshot: &Snapshot,
) -> Result<World> {
    debug!("Starting world selection");
    let worlds = snapshot.worlds();

    if worlds.is_empty() {
        bail!("No world found");
    }

    if let Some(world_name) = cli.value_of("world") {
        if let Some(world) = worlds.get(world_name) {
            return Ok(world.clone());
        } else {
            bail!("Invalid world name given: {}", world_name);
        }
    }

    if worlds.len() == 1 {
        return Ok(worlds
            .values()
            .next()
            .expect("We just checked the length!")
            .clone());
    }

    // Here, we cannot do an automatic selection, so ask the user:
    let mut worlds = worlds.iter().collect::<Vec<_>>();
    worlds.sort_by_key(|i| i.0);
    writeln!(
        output,
        "The following worlds were found, please select one:"
    )?;
    user_choice(&worlds, output).map(|&i| i.clone())
}

/// Enables the given list of mods and their dependencies.
///
/// Fails if any mod has a dependency that can not be satisfied with the locally available mods.
fn enable_mods(
    output: &mut StandardStream,
    snapshot: &Snapshot,
    world: &World,
    mods: &[&str],
) -> Result<()> {
    let mut wanted = mods.iter().map(|&s| s.to_owned()).collect::<Vec<String>>();
    let mut to_enable = Vec::<MineMod>::new();
    let game = snapshot
        .games()
        .get(&world.game_id()?)
        .ok_or_else(|| anyhow!("The game definition was not found"))?;
    let game_mods = game
        .mods()?
        .into_iter()
        .map(|m| m.mod_id())
        .collect::<Result<Vec<_>, _>>()?;

    while !wanted.is_empty() {
        let next_mod = wanted.remove(0);
        // Do we already have the mod enabled, somehow?
        if world.mods()?.contains(&next_mod) || game_mods.contains(&next_mod) {
            continue;
        }

        match snapshot.mods().get(&next_mod as &str) {
            Some(m) => {
                to_enable.push(m.clone());
                wanted.extend(m.dependencies()?);
            }
            None => bail!("Mod {} could not be found", next_mod),
        }
    }

    if to_enable.is_empty() {
        writeln!(output, "Done!")?;
        return Ok(());
    }

    writeln!(output, "Enabling {} mods:", to_enable.len())?;
    writeln!(output, "{}", to_enable.iter().join(", "))?;

    ask_continue(output)?;

    for m in to_enable {
        let mod_id = m.mod_id()?;
        world
            .enable_mod(&mod_id)
            .context(format!("Error enabling '{}'", mod_id))?;
    }

    writeln!(output, "Done!")?;
    Ok(())
}

/// Install the given mods, installing dependencies if needed.
fn install_mods(
    output: &mut StandardStream,
    snapshot: &Snapshot,
    world: &World,
    mods: &[&str],
    matches: &ArgMatches,
) -> Result<()> {
    let target_dir = Path::new(matches.value_of("target").unwrap());
    let dry_run = matches.is_present("dry-run");
    let fix_permissions = matches.is_present("fix-permissions");

    let content_db = ContentDb::new();
    let downloader = Downloader::new()?;
    let mut wanted = mods
        .iter()
        .map(|&s| Source::from_str(s))
        .collect::<Result<Vec<_>, _>>()?;

    let mut to_install = Vec::<Box<dyn ModContainer>>::new();
    let mut to_enable = Vec::<MineMod>::new();

    let game = snapshot
        .games()
        .get(&world.game_id()?)
        .ok_or_else(|| anyhow!("The game definition was not found"))?;
    let game_mods = game
        .mods()?
        .into_iter()
        .map(|m| m.mod_id())
        .collect::<Result<Vec<_>, _>>()?;

    'modloop: while !wanted.is_empty() {
        let next_mod = wanted.remove(0);

        // Special handling for mods specified by their ID, as those could already exist.
        if let Source::ModId(ref id) = next_mod {
            if let Some(m) = snapshot.mods().get(id) {
                // We have that one, just enable it and its dependencies!
                to_enable.push(m.clone());
                wanted.extend(m.dependencies()?.into_iter().map(Source::ModId));
                continue;
            } else if game_mods.contains(id) {
                // This mod is already contained in the game, nothing for us to do
                continue;
            }

            // Is this a mod that is already queued for installation?
            for mod_or_pack in &to_install {
                for m in mod_or_pack.mods()? {
                    if &m.name()? == id {
                        continue 'modloop;
                    }
                }
            }

            // This mod is not available, so we search the content DB
            writeln!(output, "Searching for candidates: {}", id)?;
            let candidates = content_db.resolve(id)?;
            if candidates.is_empty() {
                bail!("Could not find a suitable mod for '{}'", id);
            } else if candidates.len() == 1 {
                wanted.push(Source::Http(candidates.into_iter().next().unwrap().url));
            } else {
                let items = candidates
                    .into_iter()
                    .map(|c| {
                        (
                            format!("{} by {} - {}", c.title, c.author, c.short_description),
                            c,
                        )
                    })
                    .collect::<Vec<_>>();
                writeln!(
                    output,
                    "{} candidates found, please select one:",
                    items.len()
                )?;
                let candidate = user_choice(&items, output)?;
                wanted.push(Source::Http(candidate.url.clone()));
            }
        } else {
            let downloaded = downloader
                .download(&next_mod)
                .context("Failed to download mod")?;
            for m in downloaded.mods()? {
                wanted.extend(m.dependencies()?.into_iter().map(Source::ModId));
            }
            to_install.push(downloaded);
        }
    }

    writeln!(output, "Installing {} new mods:", to_install.len())?;
    writeln!(output, "{}", to_install.iter().join(", "))?;

    ask_continue(output)?;

    if dry_run {
        for m in to_install {
            let mod_id = m.name()?;
            let mod_dir = target_dir.join(&mod_id);
            writeln!(output, "Installing {} to {:?}", m, mod_dir)?;
            to_enable.extend(m.mods()?);
        }
        for m in to_enable {
            let mod_id = m.mod_id()?;
            writeln!(output, "Enabling {}", mod_id)?;
        }
        return Ok(());
    }

    for m in to_install {
        let mod_id = m.name()?;
        writeln!(output, "Installing {}", mod_id)?;
        let installed = m
            .install_to(target_dir)
            .context(format!("Error installing '{}'", mod_id))?;
        to_enable.extend(installed.mods()?);

        #[cfg(unix)]
        {
            use nix::{
                sys::stat,
                unistd::{Gid, Uid},
            };
            if fix_permissions {
                let perms = stat::stat(target_dir)?;
                let (uid, gid) = (Uid::from_raw(perms.st_uid), Gid::from_raw(perms.st_gid));
                util::chown_recursive(installed.path(), Some(uid), Some(gid))?;
            }
        }
    }

    for m in to_enable {
        let mod_id = m.mod_id()?;
        world
            .enable_mod(&mod_id)
            .context(format!("Error enabling '{}'", mod_id))?;
    }

    writeln!(output, "Done!")?;

    Ok(())
}

/// Presents the user with a choice of items and awaits a selection.
fn user_choice<'i, L: Display, I>(
    items: &'i [(L, I)],
    output: &mut StandardStream,
) -> Result<&'i I> {
    for (i, (label, _)) in items.iter().enumerate() {
        output.set_color(ColorSpec::new().set_fg(Some(Color::Blue)))?;
        write!(output, "[{}]", i)?;
        output.reset()?;
        writeln!(output, " {}", label)?;
    }

    let stdin = io::stdin();
    loop {
        write!(output, "Enter a number: ")?;
        output.flush()?;
        let mut buffer = String::new();
        stdin.read_line(&mut buffer)?;
        if let Ok(number) = buffer.trim().parse::<usize>() {
            if number < items.len() {
                return Ok(&items[number].1);
            }
        }
    }
}

/// Ask the user whether they want to continue.
///
/// Returns `Ok(())` if the program should continue, and an error otherwise.
fn ask_continue(output: &mut StandardStream) -> Result<()> {
    let stdin = io::stdin();
    loop {
        output.set_color(ColorSpec::new().set_fg(Some(Color::Yellow)))?;
        write!(output, "Continue? [Y/n] ")?;
        output.reset()?;
        output.flush()?;

        let mut buffer = String::new();
        stdin.read_line(&mut buffer)?;
        if buffer == "\n" || buffer == "Y\n" || buffer == "y\n" {
            return Ok(());
        } else if buffer == "N\n" || buffer == "n\n" {
            bail!("Cancelled by user");
        }
    }
}