pub use crate::commands::Command;
use crate::config::Config;
use helix_core::hashmap;
use helix_view::{document::Mode, info::Info, input::KeyEvent};
use serde::Deserialize;
use std::{
    borrow::Cow,
    collections::HashMap,
    ops::{Deref, DerefMut},
};

#[macro_export]
macro_rules! key {
    ($key:ident) => {
        ::helix_view::input::KeyEvent {
            code: ::helix_view::keyboard::KeyCode::$key,
            modifiers: ::helix_view::keyboard::KeyModifiers::NONE,
        }
    };
    ($($ch:tt)*) => {
        ::helix_view::input::KeyEvent {
            code: ::helix_view::keyboard::KeyCode::Char($($ch)*),
            modifiers: ::helix_view::keyboard::KeyModifiers::NONE,
        }
    };
}

/// Macro for defining the root of a `Keymap` object. Example:
///
/// ```
/// # use helix_core::hashmap;
/// # use helix_term::keymap;
/// # use helix_term::keymap::Keymap;
/// let normal_mode = keymap!({ "Normal mode"
///     "i" => insert_mode,
///     "g" => { "Goto"
///         "g" => goto_file_start,
///         "e" => goto_file_end,
///     },
///     "j" | "down" => move_line_down,
/// });
/// let keymap = Keymap::new(normal_mode);
/// ```
#[macro_export]
macro_rules! keymap {
    (@trie $cmd:ident) => {
        $crate::keymap::KeyTrie::Leaf($crate::commands::Command::$cmd)
    };

    (@trie
        { $label:literal $(sticky=$sticky:literal)? $($($key:literal)|+ => $value:tt,)+ }
    ) => {
        keymap!({ $label $(sticky=$sticky)? $($($key)|+ => $value,)+ })
    };

    (
        { $label:literal $(sticky=$sticky:literal)? $($($key:literal)|+ => $value:tt,)+ }
    ) => {
        // modified from the hashmap! macro
        {
            let _cap = hashmap!(@count $($($key),+),*);
            let mut _map = ::std::collections::HashMap::with_capacity(_cap);
            let mut _order = ::std::vec::Vec::with_capacity(_cap);
            $(
                $(
                    let _key = $key.parse::<::helix_view::input::KeyEvent>().unwrap();
                    _map.insert(
                        _key,
                        keymap!(@trie $value)
                    );
                    _order.push(_key);
                )+
            )*
            let mut _node = $crate::keymap::KeyTrieNode::new($label, _map, _order);
            $( _node.is_sticky = $sticky; )?
            $crate::keymap::KeyTrie::Node(_node)
        }
    };
}

#[derive(Debug, Clone, Deserialize)]
pub struct KeyTrieNode {
    /// A label for keys coming under this node, like "Goto mode"
    #[serde(skip)]
    name: String,
    #[serde(flatten)]
    map: HashMap<KeyEvent, KeyTrie>,
    #[serde(skip)]
    order: Vec<KeyEvent>,
    #[serde(skip)]
    pub is_sticky: bool,
}

impl KeyTrieNode {
    pub fn new(name: &str, map: HashMap<KeyEvent, KeyTrie>, order: Vec<KeyEvent>) -> Self {
        Self {
            name: name.to_string(),
            map,
            order,
            is_sticky: false,
        }
    }

    pub fn name(&self) -> &str {
        &self.name
    }

    /// Merge another Node in. Leaves and subnodes from the other node replace
    /// corresponding keyevent in self, except when both other and self have
    /// subnodes for same key. In that case the merge is recursive.
    pub fn merge(&mut self, mut other: Self) {
        for (key, trie) in std::mem::take(&mut other.map) {
            if let Some(KeyTrie::Node(node)) = self.map.get_mut(&key) {
                if let KeyTrie::Node(other_node) = trie {
                    node.merge(other_node);
                    continue;
                }
            }
            self.map.insert(key, trie);
        }
        self.set_order();
    }

    /// Sets the order of the mapping recursively since the
    /// the trie can contain child nodes without order.
    /// The order is missing from child nodes since it's not
    /// parsed from the config.toml
    fn set_order(&mut self) {
        for (&key, trie) in self.map.iter_mut() {
            if !self.order.contains(&key) {
                self.order.push(key);
            }
            // Order must be recursively set
            if let KeyTrie::Node(node) = trie {
                node.set_order();
            }
        }
    }

    pub fn infobox(&self) -> Info {
        let mut body: Vec<(&str, Vec<KeyEvent>)> = Vec::with_capacity(self.len());
        for (&key, trie) in self.iter() {
            let desc = match trie {
                KeyTrie::Leaf(cmd) => cmd.doc(),
                KeyTrie::Node(n) => n.name(),
            };
            match body.iter().position(|(d, _)| d == &desc) {
                // FIXME: multiple keys are ordered randomly (use BTreeSet)
                Some(pos) => body[pos].1.push(key),
                None => body.push((desc, vec![key])),
            }
        }
        body.sort_unstable_by_key(|(_, keys)| {
            self.order.iter().position(|&k| k == keys[0]).unwrap()
        });
        let prefix = format!("{} ", self.name());
        if body.iter().all(|(desc, _)| desc.starts_with(&prefix)) {
            body = body
                .into_iter()
                .map(|(desc, keys)| (desc.strip_prefix(&prefix).unwrap(), keys))
                .collect();
        }
        Info::new(self.name(), body)
    }

    /// Get a reference to the key trie node's order.
    pub fn order(&self) -> &[KeyEvent] {
        self.order.as_slice()
    }
}

impl Default for KeyTrieNode {
    fn default() -> Self {
        Self::new("", HashMap::new(), Vec::new())
    }
}

impl PartialEq for KeyTrieNode {
    fn eq(&self, other: &Self) -> bool {
        self.map == other.map
    }
}

impl Deref for KeyTrieNode {
    type Target = HashMap<KeyEvent, KeyTrie>;

    fn deref(&self) -> &Self::Target {
        &self.map
    }
}

impl DerefMut for KeyTrieNode {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.map
    }
}

#[derive(Debug, Clone, PartialEq, Deserialize)]
#[serde(untagged)]
pub enum KeyTrie {
    Leaf(Command),
    Node(KeyTrieNode),
}

impl KeyTrie {
    pub fn node(&self) -> Option<&KeyTrieNode> {
        match *self {
            KeyTrie::Node(ref node) => Some(node),
            KeyTrie::Leaf(_) => None,
        }
    }

    pub fn node_mut(&mut self) -> Option<&mut KeyTrieNode> {
        match *self {
            KeyTrie::Node(ref mut node) => Some(node),
            KeyTrie::Leaf(_) => None,
        }
    }

    /// Merge another KeyTrie in, assuming that this KeyTrie and the other
    /// are both Nodes. Panics otherwise.
    pub fn merge_nodes(&mut self, mut other: Self) {
        let node = std::mem::take(other.node_mut().unwrap());
        self.node_mut().unwrap().merge(node);
    }

    pub fn search(&self, keys: &[KeyEvent]) -> Option<&KeyTrie> {
        let mut trie = self;
        for key in keys {
            trie = match trie {
                KeyTrie::Node(map) => map.get(key),
                // leaf encountered while keys left to process
                KeyTrie::Leaf(_) => None,
            }?
        }
        Some(trie)
    }
}

#[derive(Debug, Clone, PartialEq)]
pub enum KeymapResultKind {
    /// Needs more keys to execute a command. Contains valid keys for next keystroke.
    Pending(KeyTrieNode),
    Matched(Command),
    /// Key was not found in the root keymap
    NotFound,
    /// Key is invalid in combination with previous keys. Contains keys leading upto
    /// and including current (invalid) key.
    Cancelled(Vec<KeyEvent>),
}

/// Returned after looking up a key in [`Keymap`]. The `sticky` field has a
/// reference to the sticky node if one is currently active.
#[derive(Debug)]
pub struct KeymapResult<'a> {
    pub kind: KeymapResultKind,
    pub sticky: Option<&'a KeyTrieNode>,
}

impl<'a> KeymapResult<'a> {
    pub fn new(kind: KeymapResultKind, sticky: Option<&'a KeyTrieNode>) -> Self {
        Self { kind, sticky }
    }
}

#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct Keymap {
    /// Always a Node
    #[serde(flatten)]
    root: KeyTrie,
    /// Stores pending keys waiting for the next key. This is relative to a
    /// sticky node if one is in use.
    #[serde(skip)]
    state: Vec<KeyEvent>,
    /// Stores the sticky node if one is activated.
    #[serde(skip)]
    sticky: Option<KeyTrieNode>,
}

impl Keymap {
    pub fn new(root: KeyTrie) -> Self {
        Keymap {
            root,
            state: Vec::new(),
            sticky: None,
        }
    }

    pub fn root(&self) -> &KeyTrie {
        &self.root
    }

    pub fn sticky(&self) -> Option<&KeyTrieNode> {
        self.sticky.as_ref()
    }

    /// Returns list of keys waiting to be disambiguated.
    pub fn pending(&self) -> &[KeyEvent] {
        &self.state
    }

    /// Lookup `key` in the keymap to try and find a command to execute. Escape
    /// key cancels pending keystrokes. If there are no pending keystrokes but a
    /// sticky node is in use, it will be cleared.
    pub fn get(&mut self, key: KeyEvent) -> KeymapResult {
        if let key!(Esc) = key {
            if !self.state.is_empty() {
                return KeymapResult::new(
                    // Note that Esc is not included here
                    KeymapResultKind::Cancelled(self.state.drain(..).collect()),
                    self.sticky(),
                );
            }
            self.sticky = None;
        }

        let first = self.state.get(0).unwrap_or(&key);
        let trie_node = match self.sticky {
            Some(ref trie) => Cow::Owned(KeyTrie::Node(trie.clone())),
            None => Cow::Borrowed(&self.root),
        };

        let trie = match trie_node.search(&[*first]) {
            Some(&KeyTrie::Leaf(cmd)) => {
                return KeymapResult::new(KeymapResultKind::Matched(cmd), self.sticky())
            }
            None => return KeymapResult::new(KeymapResultKind::NotFound, self.sticky()),
            Some(t) => t,
        };

        self.state.push(key);
        match trie.search(&self.state[1..]) {
            Some(&KeyTrie::Node(ref map)) => {
                if map.is_sticky {
                    self.state.clear();
                    self.sticky = Some(map.clone());
                }
                KeymapResult::new(KeymapResultKind::Pending(map.clone()), self.sticky())
            }
            Some(&KeyTrie::Leaf(cmd)) => {
                self.state.clear();
                return KeymapResult::new(KeymapResultKind::Matched(cmd), self.sticky());
            }
            None => KeymapResult::new(
                KeymapResultKind::Cancelled(self.state.drain(..).collect()),
                self.sticky(),
            ),
        }
    }

    pub fn merge(&mut self, other: Self) {
        self.root.merge_nodes(other.root);
    }
}

impl Deref for Keymap {
    type Target = KeyTrieNode;

    fn deref(&self) -> &Self::Target {
        self.root.node().unwrap()
    }
}

impl Default for Keymap {
    fn default() -> Self {
        Self::new(KeyTrie::Node(KeyTrieNode::default()))
    }
}

#[derive(Debug, Clone, PartialEq, Deserialize)]
#[serde(transparent)]
pub struct Keymaps(pub HashMap<Mode, Keymap>);

impl Keymaps {
    /// Returns list of keys waiting to be disambiguated in current mode.
    pub fn pending(&self) -> &[KeyEvent] {
        self.0
            .values()
            .find_map(|keymap| match keymap.pending().is_empty() {
                true => None,
                false => Some(keymap.pending()),
            })
            .unwrap_or_default()
    }
}

impl Deref for Keymaps {
    type Target = HashMap<Mode, Keymap>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl DerefMut for Keymaps {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

impl Default for Keymaps {
    fn default() -> Keymaps {
        let normal = keymap!({ "Normal mode"
            "h" | "left" => move_char_left,
            "j" | "down" => move_line_down,
            "k" | "up" => move_line_up,
            "l" | "right" => move_char_right,

            "t" => find_till_char,
            "f" => find_next_char,
            "T" => till_prev_char,
            "F" => find_prev_char,
            "r" => replace,
            "R" => replace_with_yanked,
            "A-." =>  repeat_last_motion,

            "~" => switch_case,
            "`" => switch_to_lowercase,
            "A-`" => switch_to_uppercase,

            "home" => goto_line_start,
            "end" => goto_line_end,

            "w" => move_next_word_start,
            "b" => move_prev_word_start,
            "e" => move_next_word_end,

            "W" => move_next_long_word_start,
            "B" => move_prev_long_word_start,
            "E" => move_next_long_word_end,

            "v" => select_mode,
            "G" => goto_line,
            "g" => { "Goto"
                "g" => goto_file_start,
                "e" => goto_last_line,
                "h" => goto_line_start,
                "l" => goto_line_end,
                "s" => goto_first_nonwhitespace,
                "d" => goto_definition,
                "y" => goto_type_definition,
                "r" => goto_reference,
                "i" => goto_implementation,
                "t" => goto_window_top,
                "m" => goto_window_middle,
                "b" => goto_window_bottom,
                "a" => goto_last_accessed_file,
            },
            ":" => command_mode,

            "i" => insert_mode,
            "I" => prepend_to_line,
            "a" => append_mode,
            "A" => append_to_line,
            "o" => open_below,
            "O" => open_above,

            "d" => delete_selection,
            // TODO: also delete without yanking
            "c" => change_selection,
            // TODO: also change delete without yanking

            "C" => copy_selection_on_next_line,
            "A-C" => copy_selection_on_prev_line,


            "s" => select_regex,
            "A-s" => split_selection_on_newline,
            "S" => split_selection,
            ";" => collapse_selection,
            "A-;" => flip_selections,
            "%" => select_all,
            "x" => extend_line,
            "X" => extend_to_line_bounds,
            // crop_to_whole_line

            "m" => { "Match"
                "m" => match_brackets,
                "s" => surround_add,
                "r" => surround_replace,
                "d" => surround_delete,
                "a" => select_textobject_around,
                "i" => select_textobject_inner,
            },
            "[" => { "Left bracket"
                "d" => goto_prev_diag,
                "D" => goto_first_diag,
                "space" => add_newline_above,
            },
            "]" => { "Right bracket"
                "d" => goto_next_diag,
                "D" => goto_last_diag,
                "space" => add_newline_below,
            },

            "/" => search,
            // ? for search_reverse
            "n" => search_next,
            "N" => extend_search_next,
            // N for search_prev
            "*" => search_selection,

            "u" => undo,
            "U" => redo,

            "y" => yank,
            // yank_all
            "p" => paste_after,
            // paste_all
            "P" => paste_before,

            ">" => indent,
            "<" => unindent,
            "=" => format_selections,
            "J" => join_selections,
            "K" => keep_selections,
            // TODO: and another method for inverse

            "," => keep_primary_selection,
            "A-," => remove_primary_selection,

            // "q" => record_macro,
            // "Q" => replay_macro,

            // & align selections
            // _ trim selections

            "(" => rotate_selections_backward,
            ")" => rotate_selections_forward,
            "A-(" => rotate_selection_contents_backward,
            "A-)" => rotate_selection_contents_forward,

            "esc" => normal_mode,
            "C-b" | "pageup" => page_up,
            "C-f" | "pagedown" => page_down,
            "C-u" => half_page_up,
            "C-d" => half_page_down,

            "C-w" => { "Window"
                "C-w" | "w" => rotate_view,
                "C-s" | "s" => hsplit,
                "C-v" | "v" => vsplit,
                "C-q" | "q" => wclose,
                "C-h" | "h" => jump_view_left,
                "C-j" | "j" => jump_view_down,
                "C-k" | "k" => jump_view_up,
                "C-l" | "l" => jump_view_right,
            },

            // move under <space>c
            "C-c" => toggle_comments,

            // z family for save/restore/combine from/to sels from register

            "tab" => jump_forward, // tab == <C-i>
            "C-o" => jump_backward,
            // "C-s" => save_selection,

            "space" => { "Space"
                "f" => file_picker,
                "b" => buffer_picker,
                "s" => symbol_picker,
                "a" => code_action,
                "'" => last_picker,
                "w" => { "Window"
                    "C-w" | "w" => rotate_view,
                    "C-h" | "h" => hsplit,
                    "C-v" | "v" => vsplit,
                    "C-q" | "q" => wclose,
                },
                "y" => yank_joined_to_clipboard,
                "Y" => yank_main_selection_to_clipboard,
                "p" => paste_clipboard_after,
                "P" => paste_clipboard_before,
                "R" => replace_selections_with_clipboard,
                "/" => global_search,
                "k" => hover,
            },
            "z" => { "View"
                "z" | "c" => align_view_center,
                "t" => align_view_top,
                "b" => align_view_bottom,
                "m" => align_view_middle,
                "k" => scroll_up,
                "j" => scroll_down,
                "b" => page_up,
                "f" => page_down,
                "u" => half_page_up,
                "d" => half_page_down,
            },
            "Z" => { "View" sticky=true
                "z" | "c" => align_view_center,
                "t" => align_view_top,
                "b" => align_view_bottom,
                "m" => align_view_middle,
                "k" => scroll_up,
                "j" => scroll_down,
                "b" => page_up,
                "f" => page_down,
                "u" => half_page_up,
                "d" => half_page_down,
            },

            "\"" => select_register,
            "|" => shell_pipe,
            "A-|" => shell_pipe_to,
            "!" => shell_insert_output,
            "A-!" => shell_append_output,
            "$" => shell_keep_pipe,
            "C-z" => suspend,
        });
        let mut select = normal.clone();
        select.merge_nodes(keymap!({ "Select mode"
            "h" | "left" => extend_char_left,
            "j" | "down" => extend_line_down,
            "k" | "up" => extend_line_up,
            "l" | "right" => extend_char_right,

            "w" => extend_next_word_start,
            "b" => extend_prev_word_start,
            "e" => extend_next_word_end,
            "W" => extend_next_long_word_start,
            "B" => extend_prev_long_word_start,
            "E" => extend_next_long_word_end,

            "t" => extend_till_char,
            "f" => extend_next_char,
            "T" => extend_till_prev_char,
            "F" => extend_prev_char,

            "home" => extend_to_line_start,
            "end" => extend_to_line_end,
            "esc" => exit_select_mode,

            "v" => normal_mode,
        }));
        let insert = keymap!({ "Insert mode"
            "esc" => normal_mode,

            "backspace" => delete_char_backward,
            "del" => delete_char_forward,
            "ret" => insert_newline,
            "tab" => insert_tab,
            "C-w" => delete_word_backward,

            "left" => move_char_left,
            "down" => move_line_down,
            "up" => move_line_up,
            "right" => move_char_right,
            "pageup" => page_up,
            "pagedown" => page_down,
            "home" => goto_line_start,
            "end" => goto_line_end_newline,

            "C-x" => completion,
        });
        Keymaps(hashmap!(
            Mode::Normal => Keymap::new(normal),
            Mode::Select => Keymap::new(select),
            Mode::Insert => Keymap::new(insert),
        ))
    }
}

/// Merge default config keys with user overwritten keys for custom user config.
pub fn merge_keys(mut config: Config) -> Config {
    let mut delta = std::mem::take(&mut config.keys);
    for (mode, keys) in &mut *config.keys {
        keys.merge(delta.remove(mode).unwrap_or_default())
    }
    config
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn merge_partial_keys() {
        let config = Config {
            keys: Keymaps(hashmap! {
                Mode::Normal => Keymap::new(
                    keymap!({ "Normal mode"
                        "i" => normal_mode,
                        "无" => insert_mode,
                        "z" => jump_backward,
                        "g" => { "Merge into goto mode"
                            "$" => goto_line_end,
                            "g" => delete_char_forward,
                        },
                    })
                )
            }),
            ..Default::default()
        };
        let mut merged_config = merge_keys(config.clone());
        assert_ne!(config, merged_config);

        let keymap = merged_config.keys.0.get_mut(&Mode::Normal).unwrap();
        assert_eq!(
            keymap.get(key!('i')).kind,
            KeymapResultKind::Matched(Command::normal_mode),
            "Leaf should replace leaf"
        );
        assert_eq!(
            keymap.get(key!('无')).kind,
            KeymapResultKind::Matched(Command::insert_mode),
            "New leaf should be present in merged keymap"
        );
        // Assumes that z is a node in the default keymap
        assert_eq!(
            keymap.get(key!('z')).kind,
            KeymapResultKind::Matched(Command::jump_backward),
            "Leaf should replace node"
        );
        // Assumes that `g` is a node in default keymap
        assert_eq!(
            keymap.root().search(&[key!('g'), key!('$')]).unwrap(),
            &KeyTrie::Leaf(Command::goto_line_end),
            "Leaf should be present in merged subnode"
        );
        // Assumes that `gg` is in default keymap
        assert_eq!(
            keymap.root().search(&[key!('g'), key!('g')]).unwrap(),
            &KeyTrie::Leaf(Command::delete_char_forward),
            "Leaf should replace old leaf in merged subnode"
        );
        // Assumes that `ge` is in default keymap
        assert_eq!(
            keymap.root().search(&[key!('g'), key!('e')]).unwrap(),
            &KeyTrie::Leaf(Command::goto_last_line),
            "Old leaves in subnode should be present in merged node"
        );

        assert!(merged_config.keys.0.get(&Mode::Normal).unwrap().len() > 1);
        assert!(merged_config.keys.0.get(&Mode::Insert).unwrap().len() > 0);
    }

    #[test]
    fn order_should_be_set() {
        let config = Config {
            keys: Keymaps(hashmap! {
                Mode::Normal => Keymap::new(
                    keymap!({ "Normal mode"
                        "space" => { ""
                            "s" => { ""
                                "v" => vsplit,
                                "c" => hsplit,
                            },
                        },
                    })
                )
            }),
            ..Default::default()
        };
        let mut merged_config = merge_keys(config.clone());
        assert_ne!(config, merged_config);
        let keymap = merged_config.keys.0.get_mut(&Mode::Normal).unwrap();
        // Make sure mapping works
        assert_eq!(
            keymap
                .root()
                .search(&[key!(' '), key!('s'), key!('v')])
                .unwrap(),
            &KeyTrie::Leaf(Command::vsplit),
            "Leaf should be present in merged subnode"
        );
        // Make sure an order was set during merge
        let node = keymap.root().search(&[crate::key!(' ')]).unwrap();
        assert!(!node.node().unwrap().order().is_empty())
    }
}