use std::io;
use std::io::{stdin, stdout, BufRead, BufReader, Write};
use std::process;
use std::process::Stdio;
use termion::color;
use termion::input::TermRead;
use termion::raw::IntoRawMode;
use termion::terminal_size;

use gopher;
use gopher::io_error;
use gopher::Type;
use help;
use menu::Menu;
use text::Text;

pub type Key = termion::event::Key;

pub const SCROLL_LINES: usize = 15;
pub const MAX_COLS: usize = 72;

pub struct UI {
    pages: Vec<Box<dyn View>>, // loaded views
    page: usize,               // currently focused view
    dirty: bool,               // redraw?
    running: bool,             // main ui loop running?
    pub size: (usize, usize),  // cols, rows
}

#[derive(Debug)]
pub enum Action {
    None,          // do nothing
    Back,          // back in history
    Forward,       // also history
    Open(String),  // url
    Keypress(Key), // unknown keypress
    Redraw,        // redraw everything
    Quit,          // yup
    Error(String), // error message
}

pub trait View {
    fn respond(&mut self, key: Key) -> Action;
    fn render(&self) -> String;
    fn url(&self) -> String;
    fn raw(&self) -> String;
    fn term_size(&mut self, cols: usize, rows: usize);
}

impl UI {
    pub fn new() -> UI {
        let mut size = (0, 0);
        if let Ok((cols, rows)) = terminal_size() {
            size = (cols as usize, rows as usize);
        }
        UI {
            pages: vec![],
            page: 0,
            dirty: true,
            running: true,
            size,
        }
    }

    pub fn run(&mut self) {
        self.startup();
        while self.running {
            self.draw();
            self.update();
        }
        self.shutdown();
    }

    pub fn draw(&mut self) {
        if self.dirty {
            print!(
                "{}{}{}{}",
                termion::clear::All,
                termion::cursor::Goto(1, 1),
                termion::cursor::Hide,
                self.render()
            );
            self.dirty = false;
        }
    }

    pub fn update(&mut self) {
        let mut stdout = stdout().into_raw_mode().unwrap();
        stdout.flush().unwrap();

        let action = self.process_page_input();
        self.process_action(action)
            .map_err(|e| error(&e.to_string()));
    }

    pub fn open(&mut self, url: &str) -> io::Result<()> {
        // no open loops
        if let Some(page) = self.pages.get(self.page) {
            if &page.url() == url {
                return Ok(());
            }
        }

        // non-gopher URL
        if !url.starts_with("gopher://") {
            return open_external(url);
        }

        // on-line help
        if url.starts_with("gopher://help/") {
            return self.open_help(url);
        }

        // gopher URL
        status(&format!(
            "{}Loading...{}",
            color::Fg(color::LightBlack),
            termion::cursor::Show
        ));
        let (typ, host, port, sel) = gopher::parse_url(url);
        gopher::fetch(host, port, sel)
            .and_then(|response| match typ {
                Type::Menu | Type::Search => {
                    Ok(self.add_page(Menu::from(url.to_string(), response)))
                }
                Type::Text | Type::HTML => Ok(self.add_page(Text::from(url.to_string(), response))),
                _ => Err(io_error(format!("Unsupported Gopher Response: {:?}", typ))),
            })
            .map_err(|e| io_error(format!("Error loading {}: {} ({:?})", url, e, e.kind())))
    }

    // open a phetch on-line help url, ex: gopher://help/1/types
    pub fn open_help(&mut self, url: &str) -> io::Result<()> {
        if let Some(source) = help::lookup(
            &url.trim_start_matches("gopher://help/")
                .trim_start_matches("1/"),
        ) {
            self.add_page(Menu::from(url.to_string(), source.to_string()));
            Ok(())
        } else {
            Err(gopher::io_error(format!("Help file not found: {}", url)))
        }
    }

    pub fn render(&mut self) -> String {
        if let Ok((cols, rows)) = terminal_size() {
            self.term_size(cols as usize, rows as usize);
            if !self.pages.is_empty() && self.page < self.pages.len() {
                if let Some(page) = self.pages.get_mut(self.page) {
                    page.term_size(cols as usize, rows as usize);
                    return page.render();
                }
            }
            String::from("No content to display.")
        } else {
            format!(
                "Error getting terminal size. Please file a bug: {}",
                "https://github.com/dvkt/phetch/issues/new"
            )
        }
    }

    fn startup(&mut self) {
        self.load_history();
    }

    fn shutdown(&self) {
        self.save_history();
    }

    fn config_dir_path(&self) -> Option<std::path::PathBuf> {
        let homevar = std::env::var("HOME");
        if homevar.is_err() {
            return None;
        }

        let dotdir = "~/.config/phetch".replace('~', &homevar.unwrap());
        let dotdir = std::path::Path::new(&dotdir);
        if dotdir.exists() {
            Some(std::path::PathBuf::from(dotdir))
        } else {
            None
        }
    }

    fn load_history(&mut self) {
        let dotdir = self.config_dir_path();
        if dotdir.is_none() {
            return;
        }
        let history = dotdir.unwrap().join("history");
        if let Ok(file) = std::fs::OpenOptions::new().read(true).open(history) {
            let buffered = BufReader::new(file);
            let mut lines = buffered.lines();
            while let Some(Ok(url)) = lines.next() {}
        }
    }

    fn save_history(&self) {
        let dotdir = self.config_dir_path();
        if dotdir.is_none() {
            return;
        }
        let dotdir = dotdir.unwrap();
        let mut out = String::new();
        for page in &self.pages {
            let url = page.url();
            if url.starts_with("gopher://help/") {
                continue;
            }
            out.push_str(&page.url());
            out.push('\n');
        }
        let history = dotdir.join("history");
        if let Ok(mut file) = std::fs::OpenOptions::new()
            .append(true)
            .create(true)
            .open(history)
        {
            file.write_all(out.as_ref());
        }
    }

    fn term_size(&mut self, cols: usize, rows: usize) {
        self.size = (cols, rows);
    }

    fn add_page<T: View + 'static>(&mut self, view: T) {
        self.dirty = true;
        if !self.pages.is_empty() && self.page < self.pages.len() - 1 {
            self.pages.truncate(self.page + 1);
        }
        self.pages.push(Box::from(view));
        if self.pages.len() > 1 {
            self.page += 1;
        }
    }

    fn process_page_input(&mut self) -> Action {
        if let Some(page) = self.pages.get_mut(self.page) {
            if let Ok(key) = stdin()
                .keys()
                .nth(0)
                .ok_or(Action::Error("stdin.keys() error".to_string()))
            {
                if let Ok(key) = key {
                    return page.respond(key);
                }
            }
        }

        Action::None
    }

    fn process_action(&mut self, action: Action) -> io::Result<()> {
        match action {
            Action::Quit | Action::Keypress(Key::Ctrl('q')) | Action::Keypress(Key::Ctrl('c')) => {
                self.running = false
            }
            Action::Error(e) => return Err(io_error(e)),
            Action::Redraw => self.dirty = true,
            Action::Open(url) => self.open(&url)?,
            Action::Back | Action::Keypress(Key::Left) | Action::Keypress(Key::Backspace) => {
                if self.page > 0 {
                    self.dirty = true;
                    self.page -= 1;
                }
            }
            Action::Forward | Action::Keypress(Key::Right) => {
                if self.page < self.pages.len() - 1 {
                    self.dirty = true;
                    self.page += 1;
                }
            }
            Action::Keypress(Key::Ctrl('r')) => {
                if let Some(page) = self.pages.get(self.page) {
                    let url = page.url().to_string();
                    let raw = page.raw().to_string();
                    self.add_page(Text::from(url, raw));
                }
            }
            Action::Keypress(Key::Ctrl('g')) => {
                if let Some(url) = prompt("Go to URL: ") {
                    if !url.contains("://") && !url.starts_with("gopher://") {
                        self.open(&format!("gopher://{}", url))?;
                    } else {
                        self.open(&url)?;
                    }
                }
            }
            Action::Keypress(Key::Ctrl('h')) => self.open("gopher://help/")?,
            Action::Keypress(Key::Ctrl('u')) => {
                if let Some(page) = self.pages.get(self.page) {
                    status(&format!("Current URL: {}", page.url()));
                }
            }
            Action::Keypress(Key::Ctrl('y')) => {
                if let Some(page) = self.pages.get(self.page) {
                    copy_to_clipboard(&page.url())?;
                    status(&format!("Copied {} to clipboard.", page.url()));
                }
            }
            _ => (),
        }
        Ok(())
    }
}

impl Drop for UI {
    fn drop(&mut self) {
        print!("\x1b[?25h"); // show cursor
    }
}

fn copy_to_clipboard(data: &str) -> io::Result<()> {
    spawn_os_clipboard()
        .and_then(|mut child| {
            let child_stdin = child.stdin.as_mut().unwrap();
            child_stdin.write_all(data.as_bytes())
        })
        .map_err(|e| io_error(format!("Clipboard error: {}", e)))
}

fn spawn_os_clipboard() -> io::Result<process::Child> {
    if cfg!(target_os = "macos") {
        process::Command::new("pbcopy")
            .stdin(Stdio::piped())
            .spawn()
    } else {
        process::Command::new("xclip")
            .args(&["-sel", "clip"])
            .stdin(Stdio::piped())
            .spawn()
    }
}

// runs the `open` shell command
fn open_external(url: &str) -> io::Result<()> {
    process::Command::new("open")
        .arg(url)
        .output()
        .and_then(|_| Ok(()))
}

/// Prompt user for input and return what was entered, if anything.
pub fn prompt(prompt: &str) -> Option<String> {
    let (_cols, rows) = terminal_size().unwrap();

    print!(
        "{}{}{}{}{}",
        color::Fg(color::Reset),
        termion::cursor::Goto(1, rows),
        termion::clear::CurrentLine,
        prompt,
        termion::cursor::Show,
    );
    stdout().flush();

    let mut input = String::new();
    for k in stdin().keys() {
        if let Ok(key) = k {
            match key {
                Key::Char('\n') => {
                    print!("{}{}", termion::clear::CurrentLine, termion::cursor::Hide);
                    stdout().flush();
                    return Some(input);
                }
                Key::Char(c) => input.push(c),
                Key::Esc | Key::Ctrl('c') => {
                    if input.is_empty() {
                        print!("{}{}", termion::clear::CurrentLine, termion::cursor::Hide);
                        stdout().flush();
                        return None;
                    } else {
                        input.clear();
                    }
                }
                Key::Backspace | Key::Delete => {
                    input.pop();
                }
                _ => {}
            }
        } else {
            break;
        }

        print!(
            "{}{}{}{}",
            termion::cursor::Goto(1, rows),
            termion::clear::CurrentLine,
            prompt,
            input,
        );
        stdout().flush();
    }

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

// Display a status message to the user.
pub fn status(s: &str) {
    let (_cols, rows) = terminal_size().unwrap();
    print!(
        "{}{}{}{}",
        termion::cursor::Goto(1, rows),
        termion::clear::CurrentLine,
        s,
        color::Fg(color::Reset)
    );
    stdout().flush();
}

// Display an error message to the user.
pub fn error(e: &str) {
    let (_cols, rows) = terminal_size().unwrap();
    print!(
        "{}{}{}{}{}",
        "\x1b[91m",
        termion::cursor::Goto(1, rows),
        termion::clear::CurrentLine,
        e,
        color::Fg(color::Reset)
    );
    stdout().flush();
}