use crate::{api, sys, usr};
use crate::api::console::Style;
use crate::api::fs;
use crate::api::prompt::Prompt;
use crate::api::regex::Regex;
use crate::api::syscall;
use crate::sys::fs::FileType;

use alloc::collections::btree_map::BTreeMap;
use alloc::format;
use alloc::vec::Vec;
use alloc::string::{String, ToString};

// TODO: Scan /bin
const AUTOCOMPLETE_COMMANDS: [&str; 35] = [
    "2048", "base64", "calc", "colors", "copy", "date", "delete", "dhcp", "disk", "edit",
    "env", "exit", "geotime", "goto", "help", "hex", "host", "http", "httpd", "install",
    "keyboard", "lisp", "list", "memory", "move", "net", "pci", "read",
    "shell", "socket", "tcp", "time", "user", "vga", "write"
];

#[repr(u8)]
#[derive(PartialEq)]
pub enum ExitCode {
    CommandSuccessful = 0,
    CommandUnknown    = 1,
    CommandError      = 2,
    ShellExit         = 255,
}

fn autocomplete_commands() -> Vec<String> {
    let mut res = Vec::new();
    for cmd in AUTOCOMPLETE_COMMANDS {
        res.push(cmd.to_string());
    }
    if let Ok(files) = fs::read_dir("/bin") {
        for file in files {
            res.push(file.name());
        }
    }
    res.sort();
    res
}

fn shell_completer(line: &str) -> Vec<String> {
    let mut entries = Vec::new();

    let args = split_args(line);
    let i = args.len() - 1;
    if args.len() == 1 && !args[0].starts_with('/') { // Autocomplete command
        for cmd in autocomplete_commands() {
            if let Some(entry) = cmd.strip_prefix(args[i]) {
                entries.push(entry.into());
            }
        }
    } else { // Autocomplete path
        let pathname = fs::realpath(args[i]);
        let dirname = fs::dirname(&pathname);
        let filename = fs::filename(&pathname);
        let sep = if dirname.ends_with('/') { "" } else { "/" };
        if let Ok(files) = fs::read_dir(dirname) {
            for file in files {
                let name = file.name();
                if name.starts_with(filename) {
                    let end = if file.is_dir() { "/" } else { "" };
                    let path = format!("{}{}{}{}", dirname, sep, name, end);
                    entries.push(path[pathname.len()..].into());
                }
            }
        }
    }
    entries
}

pub fn prompt_string(success: bool) -> String {
    let csi_color = Style::color("Magenta");
    let csi_error = Style::color("Red");
    let csi_reset = Style::reset();
    format!("{}>{} ", if success { csi_color } else { csi_error }, csi_reset)
}

pub fn default_env() -> BTreeMap<String, String> {
    let mut env = BTreeMap::new();

    // Copy the process environment to the shell environment
    for (key, val) in sys::process::envs() {
        env.insert(key, val);
    }

    env
}

pub fn split_args(cmd: &str) -> Vec<&str> {
    let mut args: Vec<&str> = Vec::new();
    let mut i = 0;
    let mut n = cmd.len();
    let mut is_quote = false;

    for (j, c) in cmd.char_indices() {
        if c == '#' && !is_quote {
            n = j; // Discard comments
            break;
        } else if c == ' ' && !is_quote {
            if i != j {
                args.push(&cmd[i..j]);
            }
            i = j + 1;
        } else if c == '"' {
            is_quote = !is_quote;
            if !is_quote {
                args.push(&cmd[i..j]);
            }
            i = j + 1;
        }
    }

    if i < n {
        if is_quote {
            n -= 1;
        }
        args.push(&cmd[i..n]);
    }

    if n == 0 || cmd.ends_with(' ') {
        args.push("");
    }

    args
}

fn proc(args: &[&str]) -> ExitCode {
    match args.len() {
        1 => {
            ExitCode::CommandSuccessful
        },
        2 => {
            match args[1] {
                "id" => {
                    println!("{}", sys::process::id());
                    ExitCode::CommandSuccessful
                }
                "files" => {
                    for (i, handle) in sys::process::file_handles().iter().enumerate() {
                        if let Some(resource) = handle {
                            println!("{}: {:?}", i, resource);
                        }
                    }
                    ExitCode::CommandSuccessful
                }
                _ => {
                    ExitCode::CommandError
                }
            }
        },
        _ => {
            ExitCode::CommandError
        }
    }
}

fn change_dir(args: &[&str]) -> ExitCode {
    match args.len() {
        1 => {
            println!("{}", sys::process::dir());
            ExitCode::CommandSuccessful
        },
        2 => {
            let mut pathname = fs::realpath(args[1]);
            if pathname.len() > 1 {
                pathname = pathname.trim_end_matches('/').into();
            }
            if api::fs::is_dir(&pathname) {
                sys::process::set_dir(&pathname);
                ExitCode::CommandSuccessful
            } else {
                error!("File not found '{}'", pathname);
                ExitCode::CommandError
            }
        },
        _ => {
            ExitCode::CommandError
        }
    }
}

pub fn exec(cmd: &str, env: &mut BTreeMap<String, String>) -> ExitCode {
    let mut cmd = cmd.to_string();

    // Replace `$key` with its value in the environment or an empty string
    let re = Regex::new("\\$\\w+");
    while let Some((a, b)) = re.find(&cmd) {
        let key: String = cmd.chars().skip(a + 1).take(b - a - 1).collect();
        let val = env.get(&key).map_or("", String::as_str);
        cmd = cmd.replace(&format!("${}", key), &val);
    }

    // Set env var like `foo=42` or `bar = "Hello, World!"
    if Regex::new("^\\w+ *= *\\S*$").is_match(&cmd) {
        let mut iter = cmd.splitn(2, '=');
        let key = iter.next().unwrap_or("").trim().to_string();
        let val = iter.next().unwrap_or("").trim().to_string();
        env.insert(key, val);
        return ExitCode::CommandSuccessful
    }

    let mut args = split_args(&cmd);

    // Redirections like `print hello => /tmp/hello`
    // Pipes like `print hello -> write /tmp/hello` or `p hello > w /tmp/hello`
    let mut is_redirected = false;
    let mut n = args.len();
    let mut i = 0;
    loop {
        if i == n {
            break;
        }

        let mut is_fat_arrow = false;
        let mut is_thin_arrow = false;
        let mut left_handle;

        if Regex::new("<=+").is_match(args[i]) { // Redirect input stream
            is_fat_arrow = true;
            left_handle = 0;
        } else if Regex::new("\\d*=+>").is_match(args[i]) { // Redirect output stream(s)
            is_fat_arrow = true;
            left_handle = 1;
        } else if Regex::new("\\d*-*>\\d*").is_match(args[i]) { // Pipe output stream(s)
            is_thin_arrow = true;
            left_handle = 1;
            // TODO: right_handle?
        } else {
            i += 1;
            continue;
        }

        let s = args[i].chars().take_while(|c| c.is_numeric()).collect::<String>();
        if let Ok(h) = s.parse() {
            left_handle = h;
        }

        if is_fat_arrow { // Redirections
            is_redirected = true;
            if i == n - 1 {
                println!("Could not parse path for redirection");
                return ExitCode::CommandError;
            }
            let path = args[i + 1];
            if api::fs::reopen(path, left_handle).is_err() {
                println!("Could not open path for redirection");
                return ExitCode::CommandError;
            }
            args.remove(i); // Remove redirection from args
            args.remove(i); // Remove path from args
            n -= 2;
        } else if is_thin_arrow { // TODO: Implement pipes
            println!("Could not parse arrow");
            return ExitCode::CommandError;
        }
    }

    let res = match args[0] {
        ""                     => ExitCode::CommandSuccessful,
        "a"                    => ExitCode::CommandUnknown,
        "b"                    => ExitCode::CommandUnknown,
        "c" | "copy"           => usr::copy::main(&args),
        "d" | "del" | "delete" => usr::delete::main(&args),
        "e" | "edit"           => usr::editor::main(&args),
        "f" | "find"           => usr::find::main(&args),
        "g" | "go" | "goto"    => change_dir(&args),
        "h" | "help"           => usr::help::main(&args),
        "i"                    => ExitCode::CommandUnknown,
        "j"                    => ExitCode::CommandUnknown,
        "k"                    => ExitCode::CommandUnknown,
        "l" | "list"           => usr::list::main(&args),
        "m" | "move"           => usr::r#move::main(&args),
        "n"                    => ExitCode::CommandUnknown,
        "o"                    => ExitCode::CommandUnknown,
        "q" | "quit" | "exit"  => ExitCode::ShellExit,
        "r" | "read"           => usr::read::main(&args),
        "s"                    => ExitCode::CommandUnknown,
        "t"                    => ExitCode::CommandUnknown,
        "u"                    => ExitCode::CommandUnknown,
        "v"                    => ExitCode::CommandUnknown,
        "w" | "write"          => usr::write::main(&args),
        "x"                    => ExitCode::CommandUnknown,
        "y"                    => ExitCode::CommandUnknown,
        "z"                    => ExitCode::CommandUnknown,
        "vga"                  => usr::vga::main(&args),
        "sh" | "shell"         => usr::shell::main(&args),
        "calc"                 => usr::calc::main(&args),
        "base64"               => usr::base64::main(&args),
        "date"                 => usr::date::main(&args),
        "env"                  => usr::env::main(&args),
        "hex"                  => usr::hex::main(&args),
        "net"                  => usr::net::main(&args),
        "dhcp"                 => usr::dhcp::main(&args),
        "http"                 => usr::http::main(&args),
        "httpd"                => usr::httpd::main(&args),
        "socket"               => usr::socket::main(&args),
        "tcp"                  => usr::tcp::main(&args),
        "host"                 => usr::host::main(&args),
        "install"              => usr::install::main(&args),
        "geotime"              => usr::geotime::main(&args),
        "colors"               => usr::colors::main(&args),
        "dsk" | "disk"         => usr::disk::main(&args),
        "user"                 => usr::user::main(&args),
        "mem" | "memory"       => usr::memory::main(&args),
        "kb" | "keyboard"      => usr::keyboard::main(&args),
        "lisp"                 => usr::lisp::main(&args),
        "chess"                => usr::chess::main(&args),
        "beep"                 => usr::beep::main(&args),
        "elf"                  => usr::elf::main(&args),
        "pci"                  => usr::pci::main(&args),
        "2048"                 => usr::pow::main(&args),
        "time"                 => usr::time::main(&args),
        "proc"                 => proc(&args),
        _                      => {
            let mut path = fs::realpath(args[0]);
            if path.len() > 1 {
                path = path.trim_end_matches('/').into();
            }
            match syscall::info(&path).map(|info| info.kind()) {
                Some(FileType::Dir) => {
                    sys::process::set_dir(&path);
                    ExitCode::CommandSuccessful
                }
                Some(FileType::File) => {
                    if api::process::spawn(&path, &args[1..]).is_ok() {
                        // TODO: get exit code
                        ExitCode::CommandSuccessful
                    } else {
                        error!("'{}' is not executable", path);
                        ExitCode::CommandError
                    }
                }
                _ => {
                    // TODO: add aliases command instead of hardcoding them
                    let name = match args[0] {
                        "p" => "print",
                        arg => arg,
                    };
                    if api::process::spawn(&format!("/bin/{}", name), &args).is_ok() {
                        ExitCode::CommandSuccessful
                    } else {
                        error!("Could not execute '{}'", cmd);
                        ExitCode::CommandUnknown
                    }
                }
            }
        }
    };

    // TODO: Remove this when redirections are done in spawned process
    if is_redirected {
        for i in 0..3 {
            api::fs::reopen("/dev/console", i).ok();
        }
    }

    res
}

fn repl(env: &mut BTreeMap<String, String>) -> usr::shell::ExitCode {
    println!();

    let mut prompt = Prompt::new();
    let history_file = "~/.shell-history";
    prompt.history.load(history_file);
    prompt.completion.set(&shell_completer);

    let mut success = true;
    while let Some(cmd) = prompt.input(&prompt_string(success)) {
        match exec(&cmd, env) {
            ExitCode::CommandSuccessful => {
                success = true;
            },
            ExitCode::ShellExit => {
                break;
            },
            _ => {
                success = false;
            },
        }
        prompt.history.add(&cmd);
        prompt.history.save(history_file);
        sys::console::drain();
        println!();
    }
    print!("\x1b[2J\x1b[1;1H"); // Clear screen and move cursor to top
    ExitCode::CommandSuccessful
}

pub fn main(args: &[&str]) -> ExitCode {
    let mut env = default_env();

    if args.len() < 2 {
        env.insert(0.to_string(), args[0].to_string());

        repl(&mut env)
    } else {
        env.insert(0.to_string(), args[1].to_string());

        // Add script arguments to the environment as `$1`, `$2`, `$3`, ...
        for (i, arg) in args[2..].iter().enumerate() {
            env.insert((i + 1).to_string(), arg.to_string());
        }

        let pathname = args[1];
        if let Ok(contents) = api::fs::read_to_string(pathname) {
            for line in contents.split('\n') {
                if !line.is_empty() {
                    exec(line, &mut env);
                }
            }
            ExitCode::CommandSuccessful
        } else {
            println!("File not found '{}'", pathname);
            ExitCode::CommandError
        }
    }
}

#[test_case]
fn test_shell() {
    use alloc::string::ToString;

    sys::fs::mount_mem();
    sys::fs::format_mem();
    usr::install::copy_files(false);

    let mut env = default_env();

    // Redirect standard output
    exec("print test1 => /test", &mut env);
    assert_eq!(api::fs::read_to_string("/test"), Ok("test1\n".to_string()));

    // Overwrite content of existing file
    exec("print test2 => /test", &mut env);
    assert_eq!(api::fs::read_to_string("/test"), Ok("test2\n".to_string()));

    // Redirect standard output explicitely
    exec("print test3 1=> /test", &mut env);
    assert_eq!(api::fs::read_to_string("/test"), Ok("test3\n".to_string()));

    // Redirect standard error explicitely
    exec("hex /nope 2=> /test", &mut env);
    assert!(api::fs::read_to_string("/test").unwrap().contains("File not found '/nope'"));

    exec("b = 42", &mut env);
    exec("print a $b $c d => /test", &mut env);
    assert_eq!(api::fs::read_to_string("/test"), Ok("a 42 d\n".to_string()));

    sys::fs::dismount();
}