//! The goal of this mod is to ensure the launcher shell function
//! is available i.e. the `br` shell function can be used to launch
//! broot (and thus make it possible to execute some commands, like `cd`,
//! from the starting shell.
//!
//! When everybody's OK, the resulting config dir looks like this:
//!
//!    ~/.config/broot
//!    ├──conf.toml
//!    └──launcher
//!       ├──bash
//!       │  ├──1
//!       │  └──br -> /home/dys/.config/broot/launcher/bash/1
//!       └──installed
//!
//! and a "source .config/broot/launcher/bash/br" line is written in
//! the .bashrc file (and the .zshrc file if found)
//!
//!
//! If the user refused the installation, a "refused" file takes the
//! place of the "installed" one.
//!
//! if we start to handle several shell families, we'll make the appropriate
//! structure and versions will be per shell function. Right now it would be
//! useless as we only know how to handle bash and zsh.

use std::fs;
use std::fs::OpenOptions;
use std::io::{self, BufRead, BufReader, Write};
use std::os::unix::fs::symlink;
use std::path::Path;

use directories::UserDirs;
use termion::style;

use crate::cli::{self, AppLaunchArgs};
use crate::conf;

const BASH_FUNC_VERSION: usize = 1;

// This script has been tested on bash and zsh.
// It's installed under the bash name (~/.config/broot
// but linked from both the .bashrc and the .zshrc files
const BASH_FUNC: &str = r#"
# This script was automatically generated by the broot function
# More information can be found in https://github.com/Canop/broot/blob/master/documentation.md

# This function starts broot and executes the command
# it produces, if any.
# It's needed because some shell commands, like `cd`,
# have no useful effect if executed in a subshell.
function br {
    f=$(mktemp)
    (
	set +e
	broot --outcmd "$f" "$@"
	code=$?
	if [ "$code" != 0 ]; then
	    rm -f "$f"
	    exit "$code"
	fi
    )
    code=$?
    if [ "$code" != 0 ]; then
	return "$code"
    fi
    d=$(cat "$f")
    rm -f "$f"
    eval "$d"
}
"#;

const BASH_COMPATIBLE_RC_FILES: &[&str] = &[".bashrc", ".zshrc"];

// make sure the bash script and symlink are installed
// but don't touch the shellrc files
// (i.e. this isn't enough to make the function available)
fn ensure_bash_script_installed(launcher_dir: &Path) -> io::Result<()> {
    let shellfamily = "bash";
    let dir = launcher_dir.join(&shellfamily);
    let link_path = dir.join("br");
    let link_present = link_path.exists();
    let script_path = dir.join(BASH_FUNC_VERSION.to_string());
    let func_present = script_path.exists();
    if !func_present {
        info!("script_path not present: writing it");
        fs::create_dir_all(dir)?;
        fs::write(&script_path, BASH_FUNC)?;
        if link_present {
            fs::remove_file(&link_path)?;
        }
    }
    if !func_present || !link_present {
        info!("creating link from {:?} to {:?}", &link_path, &script_path);
        symlink(&script_path, &link_path)?;
    }
    Ok(())
}

fn file_contains_line(path: &Path, searched_line: &str) -> io::Result<bool> {
    for line in BufReader::new(fs::File::open(path)?).lines() {
        if line? == searched_line {
            return Ok(true);
        }
    }
    Ok(false)
}

/// return true if the application should quit
fn maybe_patch_all_rcfiles(
    launcher_dir: &Path,
    installation_required: bool,
) -> io::Result<bool> {
    let installed_path = launcher_dir.join("installed");
    if installed_path.exists() {
        debug!("*installed* file found");
        // everything seems OK
        // Note that if a new shell has been installed, we don't
        // look again at all the .shellrc files, by design.
        // This means the user having installed a new shell after
        // broot should run `broot --install`
        if !installation_required {
            return Ok(false);
        }
    }
    let refused_path = launcher_dir.join("refused");
    if refused_path.exists() {
        debug!("*refused* file found :(");
        if installation_required {
            fs::remove_file(&refused_path)?;
        } else {
            // user doesn't seem to want the shell function
            return Ok(false);
        }
    }
    // it looks like the shell function is neither installed nor refused
    let homedir_path = match UserDirs::new() {
        Some(user_dirs) => user_dirs.home_dir().to_path_buf(),
        None => {
            warn!("no home directory found!");
            return Ok(false);
        }
    };
    let rc_files: Vec<_> = BASH_COMPATIBLE_RC_FILES
        .iter()
        .map(|name| (name, homedir_path.join(name)))
        .filter(|t| t.1.exists())
        .collect();
    if rc_files.is_empty() {
        warn!("no bash compatible rc file found, no installation possible");
        if installation_required {
            println!( "no rcfile found, we can't install the br function");
        }
        return Ok(installation_required);
    }
    if !installation_required {
        println!(
            "{}Broot{} should be launched using a shell function",
            style::Bold,
            style::Reset
        );
        println!("(see https://github.com/Canop/broot for explanations).");
        println!("The function is either missing, old or badly installed.");
        let proceed = cli::ask_authorization(&format!(
            "Can I add a line to {:?} ? [Y n]",
            rc_files.iter().map(|f| *f.0).collect::<Vec<&str>>().join(" and "),
        ))?;
        debug!("proceed: {:?}", proceed);
        if !proceed {
            // user doesn't want the shell function, let's remember it
            fs::write(
                &refused_path,
                "to install the br function, run broot --install\n",
            )?;
            println!("Okey. If you change your mind, use ̀ broot --install`.");
            return Ok(false);
        }
    }

    let br_path = launcher_dir.join("bash").join("br");
    let source_line = format!("source {}", br_path.to_string_lossy());
    let mut changes_made = false;
    for rc_file in rc_files {
        if file_contains_line(&rc_file.1, &source_line)? {
            println!("{} already patched, no change made.", rc_file.0);
        } else {
            let mut shellrc = OpenOptions::new()
                .write(true)
                .append(true)
                .open(&rc_file.1)?;
            shellrc.write_all(b"\n")?;
            shellrc.write_all(source_line.as_bytes())?;
            println!(
                "{} successfully patched, you should now refresh it with.",
                rc_file.0
            );
            println!("  source {}", rc_file.1.to_string_lossy());
            changes_made = true;
        }
        // signal if there's an old br function declared in the shellrc file
        // (which was the normal way to install before broot 0.6)
        if file_contains_line(&rc_file.1, "function br {")? {
            println!(
                "Your {} contains another br function, maybe dating from an old version of broot.",
                rc_file.0
            );
            println!("You should remove it.");
        }
    }
    if changes_made {
        println!(
            "You should afterwards start broot with just {}br{}.",
            style::Bold,
            style::Reset
        );
    }
    // and remember we did it
    fs::write(
        &installed_path,
        "to reinstall the br function, run broot --install\n",
    )?;
    Ok(changes_made)
}

/// check whether the shell function is installed, install
/// it if it wasn't refused before or if broot is launched
/// with --install.
/// returns true if the app should quit
pub fn init(launch_args: &AppLaunchArgs) -> io::Result<bool> {
    let launcher_dir = conf::dir().join("launcher");
    ensure_bash_script_installed(&launcher_dir)?;
    maybe_patch_all_rcfiles(&launcher_dir, launch_args.install)
}