use std::{io, iter::repeat, ops::Rem};

use crate::theme::{SimpleTheme, TermThemeRenderer, Theme};

use console::{Key, Term};

/// Renders a multi select prompt.
pub struct MultiSelect<'a> {
    defaults: Vec<bool>,
    items: Vec<String>,
    prompt: Option<String>,
    clear: bool,
    theme: &'a dyn Theme,
    paged: bool,
}

impl<'a> Default for MultiSelect<'a> {
    fn default() -> MultiSelect<'a> {
        MultiSelect::new()
    }
}

impl<'a> MultiSelect<'a> {
    /// Creates a multi select prompt.
    pub fn new() -> MultiSelect<'static> {
        MultiSelect::with_theme(&SimpleTheme)
    }

    /// Creates a multi select prompt with a specific theme.
    pub fn with_theme(theme: &'a dyn Theme) -> MultiSelect<'a> {
        MultiSelect {
            items: vec![],
            defaults: vec![],
            clear: true,
            prompt: None,
            theme,
            paged: false,
        }
    }

    /// Enables or disables paging
    pub fn paged(&mut self, val: bool) -> &mut MultiSelect<'a> {
        self.paged = val;
        self
    }

    /// Sets the clear behavior of the menu.
    ///
    /// The default is to clear the menu.
    pub fn clear(&mut self, val: bool) -> &mut MultiSelect<'a> {
        self.clear = val;
        self
    }

    /// Sets a defaults for the menu.
    pub fn defaults(&mut self, val: &[bool]) -> &mut MultiSelect<'a> {
        self.defaults = val
            .to_vec()
            .iter()
            .cloned()
            .chain(repeat(false))
            .take(self.items.len())
            .collect();
        self
    }

    /// Add a single item to the selector.
    #[inline]
    pub fn item<T: ToString>(&mut self, item: T) -> &mut MultiSelect<'a> {
        self.item_checked(item, false)
    }

    /// Add a single item to the selector with a default checked state.
    pub fn item_checked<T: ToString>(&mut self, item: T, checked: bool) -> &mut MultiSelect<'a> {
        self.items.push(item.to_string());
        self.defaults.push(checked);
        self
    }

    /// Adds multiple items to the selector.
    pub fn items<T: ToString>(&mut self, items: &[T]) -> &mut MultiSelect<'a> {
        for item in items {
            self.items.push(item.to_string());
            self.defaults.push(false);
        }
        self
    }

    /// Adds multiple items to the selector with checked state
    pub fn items_checked<T: ToString>(&mut self, items: &[(T, bool)]) -> &mut MultiSelect<'a> {
        for &(ref item, checked) in items {
            self.items.push(item.to_string());
            self.defaults.push(checked);
        }
        self
    }

    /// Prefaces the menu with a prompt.
    ///
    /// When a prompt is set the system also prints out a confirmation after
    /// the selection.
    pub fn with_prompt<S: Into<String>>(&mut self, prompt: S) -> &mut MultiSelect<'a> {
        self.prompt = Some(prompt.into());
        self
    }

    /// Enables user interaction and returns the result.
    ///
    /// The user can select the items with the space bar and on enter
    /// the selected items will be returned.
    pub fn interact(&self) -> io::Result<Vec<usize>> {
        self.interact_on(&Term::stderr())
    }

    /// Like `interact` but allows a specific terminal to be set.
    pub fn interact_on(&self, term: &Term) -> io::Result<Vec<usize>> {
        let mut page = 0;

        let capacity = if self.paged {
            term.size().0 as usize - 1
        } else {
            self.items.len()
        };

        let pages = (self.items.len() / capacity) + 1;
        let mut render = TermThemeRenderer::new(term, self.theme);
        let mut sel = 0;

        if let Some(ref prompt) = self.prompt {
            render.multi_select_prompt(prompt)?;
        }

        let mut size_vec = Vec::new();

        for items in self
            .items
            .iter()
            .flat_map(|i| i.split('\n'))
            .collect::<Vec<_>>()
        {
            let size = &items.len();
            size_vec.push(size.clone());
        }

        let mut checked: Vec<bool> = self.defaults.clone();

        loop {
            for (idx, item) in self
                .items
                .iter()
                .enumerate()
                .skip(page * capacity)
                .take(capacity)
            {
                render.multi_select_prompt_item(item, checked[idx], sel == idx)?;
            }

            term.hide_cursor()?;
            term.flush()?;

            match term.read_key()? {
                Key::ArrowDown | Key::Char('j') => {
                    if sel == !0 {
                        sel = 0;
                    } else {
                        sel = (sel as u64 + 1).rem(self.items.len() as u64) as usize;
                    }
                }
                Key::ArrowUp | Key::Char('k') => {
                    if sel == !0 {
                        sel = self.items.len() - 1;
                    } else {
                        sel = ((sel as i64 - 1 + self.items.len() as i64)
                            % (self.items.len() as i64)) as usize;
                    }
                }
                Key::ArrowLeft | Key::Char('h') => {
                    if self.paged {
                        if page == 0 {
                            page = pages - 1;
                        } else {
                            page -= 1;
                        }

                        sel = page * capacity;
                    }
                }
                Key::ArrowRight | Key::Char('l') => {
                    if self.paged {
                        if page == pages - 1 {
                            page = 0;
                        } else {
                            page += 1;
                        }

                        sel = page * capacity;
                    }
                }
                Key::Char(' ') => {
                    checked[sel] = !checked[sel];
                }
                Key::Escape => {
                    if self.clear {
                        render.clear()?;
                    }

                    if let Some(ref prompt) = self.prompt {
                        render.multi_select_prompt_selection(prompt, &[][..])?;
                    }

                    term.show_cursor()?;
                    term.flush()?;

                    return Ok(self
                        .defaults
                        .clone()
                        .into_iter()
                        .enumerate()
                        .filter_map(|(idx, checked)| if checked { Some(idx) } else { None })
                        .collect());
                }
                Key::Enter => {
                    if self.clear {
                        render.clear()?;
                    }

                    if let Some(ref prompt) = self.prompt {
                        let selections: Vec<_> = checked
                            .iter()
                            .enumerate()
                            .filter_map(|(idx, &checked)| {
                                if checked {
                                    Some(self.items[idx].as_str())
                                } else {
                                    None
                                }
                            })
                            .collect();

                        render.multi_select_prompt_selection(prompt, &selections[..])?;
                    }

                    term.show_cursor()?;
                    term.flush()?;

                    return Ok(checked
                        .into_iter()
                        .enumerate()
                        .filter_map(|(idx, checked)| if checked { Some(idx) } else { None })
                        .collect());
                }
                _ => {}
            }

            if sel < page * capacity || sel >= (page + 1) * capacity {
                page = sel / capacity;
            }

            render.clear_preserve_prompt(&size_vec)?;
        }
    }
}