use crate::compositor::{Component, Compositor, Context, EventResult};
use crossterm::event::{Event, KeyCode, KeyEvent, KeyModifiers};
use tui::{
    buffer::Buffer as Surface,
    layout::Rect,
    style::{Color, Style},
};

use std::borrow::Cow;

use helix_core::{Position, Transaction};
use helix_view::Editor;

use crate::commands;
use crate::ui::{menu, Markdown, Menu, Popup, PromptEvent};

use helix_lsp::lsp;
use lsp::CompletionItem;

impl menu::Item for CompletionItem {
    fn filter_text(&self) -> &str {
        self.filter_text.as_ref().unwrap_or(&self.label).as_str()
    }

    fn label(&self) -> &str {
        self.label.as_str()
    }

    fn row(&self) -> menu::Row {
        menu::Row::new(vec![
            menu::Cell::from(self.label.as_str()),
            menu::Cell::from(match self.kind {
                Some(lsp::CompletionItemKind::Text) => "text",
                Some(lsp::CompletionItemKind::Method) => "method",
                Some(lsp::CompletionItemKind::Function) => "function",
                Some(lsp::CompletionItemKind::Constructor) => "constructor",
                Some(lsp::CompletionItemKind::Field) => "field",
                Some(lsp::CompletionItemKind::Variable) => "variable",
                Some(lsp::CompletionItemKind::Class) => "class",
                Some(lsp::CompletionItemKind::Interface) => "interface",
                Some(lsp::CompletionItemKind::Module) => "module",
                Some(lsp::CompletionItemKind::Property) => "property",
                Some(lsp::CompletionItemKind::Unit) => "unit",
                Some(lsp::CompletionItemKind::Value) => "value",
                Some(lsp::CompletionItemKind::Enum) => "enum",
                Some(lsp::CompletionItemKind::Keyword) => "keyword",
                Some(lsp::CompletionItemKind::Snippet) => "snippet",
                Some(lsp::CompletionItemKind::Color) => "color",
                Some(lsp::CompletionItemKind::File) => "file",
                Some(lsp::CompletionItemKind::Reference) => "reference",
                Some(lsp::CompletionItemKind::Folder) => "folder",
                Some(lsp::CompletionItemKind::EnumMember) => "enum_member",
                Some(lsp::CompletionItemKind::Constant) => "constant",
                Some(lsp::CompletionItemKind::Struct) => "struct",
                Some(lsp::CompletionItemKind::Event) => "event",
                Some(lsp::CompletionItemKind::Operator) => "operator",
                Some(lsp::CompletionItemKind::TypeParameter) => "type_param",
                None => "",
            }),
            // self.detail.as_deref().unwrap_or("")
            // self.label_details
            //     .as_ref()
            //     .or(self.detail())
            //     .as_str(),
        ])
    }
}

/// Wraps a Menu.
pub struct Completion {
    popup: Popup<Menu<CompletionItem>>, // TODO: Popup<Menu> need to be able to access contents.
    trigger_offset: usize,
    // TODO: maintain a completioncontext with trigger kind & trigger char
}

impl Completion {
    pub fn new(
        items: Vec<CompletionItem>,
        offset_encoding: helix_lsp::OffsetEncoding,
        trigger_offset: usize,
    ) -> Self {
        // let items: Vec<CompletionItem> = Vec::new();
        let mut menu = Menu::new(items, move |editor: &mut Editor, item, event| {
            match event {
                PromptEvent::Abort => {
                    // revert state
                    // let id = editor.view().doc;
                    // let doc = &mut editor.documents[id];
                    // doc.state = snapshot.clone();
                }
                PromptEvent::Validate => {
                    let (view, doc) = current!(editor);

                    // revert state to what it was before the last update
                    // doc.state = snapshot.clone();

                    // extract as fn(doc, item):

                    // TODO: need to apply without composing state...
                    // TODO: need to update lsp on accept/cancel by diffing the snapshot with
                    // the final state?
                    // -> on update simply update the snapshot, then on accept redo the call,
                    // finally updating doc.changes + notifying lsp.
                    //
                    // or we could simply use doc.undo + apply when changing between options

                    // always present here
                    let item = item.unwrap();

                    use helix_lsp::{lsp, util};

                    // if more text was entered, remove it
                    let cursor = doc.selection(view.id).cursor();
                    if trigger_offset < cursor {
                        let remove = Transaction::change(
                            doc.text(),
                            vec![(trigger_offset, cursor, None)].into_iter(),
                        );
                        doc.apply(&remove, view.id);
                    }

                    use helix_lsp::OffsetEncoding;
                    let transaction = if let Some(edit) = &item.text_edit {
                        let edit = match edit {
                            lsp::CompletionTextEdit::Edit(edit) => edit.clone(),
                            lsp::CompletionTextEdit::InsertAndReplace(item) => {
                                unimplemented!("completion: insert_and_replace {:?}", item)
                            }
                        };
                        util::generate_transaction_from_edits(
                            doc.text(),
                            vec![edit],
                            offset_encoding, // TODO: should probably transcode in Client
                        )
                    } else {
                        let text = item.insert_text.as_ref().unwrap_or(&item.label);
                        let cursor = doc.selection(view.id).cursor();
                        Transaction::change(
                            doc.text(),
                            vec![(cursor, cursor, Some(text.as_str().into()))].into_iter(),
                        )
                    };

                    doc.apply(&transaction, view.id);

                    // TODO: merge edit with additional_text_edits
                    if let Some(additional_edits) = &item.additional_text_edits {
                        // gopls uses this to add extra imports
                        if !additional_edits.is_empty() {
                            let transaction = util::generate_transaction_from_edits(
                                doc.text(),
                                additional_edits.clone(),
                                offset_encoding, // TODO: should probably transcode in Client
                            );
                            doc.apply(&transaction, view.id);
                        }
                    }
                }
                _ => (),
            };
        });
        let popup = Popup::new(menu);
        Self {
            popup,
            trigger_offset,
        }
    }

    pub fn update(&mut self, cx: &mut commands::Context) {
        // recompute menu based on matches
        let menu = self.popup.contents_mut();
        let (view, doc) = current!(cx.editor);

        // cx.hooks()
        // cx.add_hook(enum type,  ||)
        // cx.trigger_hook(enum type, &str, ...) <-- there has to be enough to identify doc/view
        // callback with editor & compositor
        //
        // trigger_hook sends event into channel, that's consumed in the global loop and
        // triggers all registered callbacks
        // TODO: hooks should get processed immediately so maybe do it after select!(), before
        // looping?

        let cursor = doc.selection(view.id).cursor();
        if self.trigger_offset <= cursor {
            let fragment = doc.text().slice(self.trigger_offset..cursor);
            let text = Cow::from(fragment);
            // TODO: logic is same as ui/picker
            menu.score(&text);
        }
    }

    pub fn is_empty(&self) -> bool {
        self.popup.contents().is_empty()
    }
}

// need to:
// - trigger on the right trigger char
//   - detect previous open instance and recycle
// - update after input, but AFTER the document has changed
// - if no more matches, need to auto close
//
// missing bits:
// - a more robust hook system: emit to a channel, process in main loop
// - a way to find specific layers in compositor
// - components register for hooks, then unregister when terminated
// ... since completion is a special case, maybe just build it into doc/render?

impl Component for Completion {
    fn handle_event(&mut self, event: Event, cx: &mut Context) -> EventResult {
        // let the Editor handle Esc instead
        if let Event::Key(KeyEvent {
            code: KeyCode::Esc, ..
        }) = event
        {
            return EventResult::Ignored;
        }
        self.popup.handle_event(event, cx)
    }

    fn required_size(&mut self, viewport: (u16, u16)) -> Option<(u16, u16)> {
        self.popup.required_size(viewport)
    }

    fn render(&self, area: Rect, surface: &mut Surface, cx: &mut Context) {
        self.popup.render(area, surface, cx);

        // TODO: if we have a selection, render a markdown popup on top/below with info
        if let Some(option) = self.popup.contents().selection() {
            // need to render:
            // option.detail
            // ---
            // option.documentation

            let (view, doc) = current!(cx.editor);
            let language = doc
                .language()
                .and_then(|scope| scope.strip_prefix("source."))
                .unwrap_or("");
            let cursor_pos = doc.selection(view.id).cursor();
            let cursor_pos = (helix_core::coords_at_pos(doc.text().slice(..), cursor_pos).row
                - view.first_line) as u16;

            let doc = match &option.documentation {
                Some(lsp::Documentation::String(contents))
                | Some(lsp::Documentation::MarkupContent(lsp::MarkupContent {
                    kind: lsp::MarkupKind::PlainText,
                    value: contents,
                })) => {
                    // TODO: convert to wrapped text
                    Markdown::new(
                        format!(
                            "```{}\n{}\n```\n{}",
                            language,
                            option.detail.as_deref().unwrap_or_default(),
                            contents.clone()
                        ),
                        cx.editor.syn_loader.clone(),
                    )
                }
                Some(lsp::Documentation::MarkupContent(lsp::MarkupContent {
                    kind: lsp::MarkupKind::Markdown,
                    value: contents,
                })) => {
                    // TODO: set language based on doc scope
                    Markdown::new(
                        format!(
                            "```{}\n{}\n```\n{}",
                            language,
                            option.detail.as_deref().unwrap_or_default(),
                            contents.clone()
                        ),
                        cx.editor.syn_loader.clone(),
                    )
                }
                None if option.detail.is_some() => {
                    // TODO: copied from above

                    // TODO: set language based on doc scope
                    Markdown::new(
                        format!(
                            "```{}\n{}\n```",
                            language,
                            option.detail.as_deref().unwrap_or_default(),
                        ),
                        cx.editor.syn_loader.clone(),
                    )
                }
                None => return,
            };

            let half = area.height / 2;
            let height = 15.min(half);
            // we want to make sure the cursor is visible (not hidden behind the documentation)
            let y = if cursor_pos + view.area.y
                >= (cx.editor.tree.area().height - height - 2/* statusline + commandline */)
            {
                0
            } else {
                // -2 to subtract command line + statusline. a bit of a hack, because of splits.
                area.height.saturating_sub(height).saturating_sub(2)
            };

            let area = Rect::new(0, y, area.width, height);

            // clear area
            let background = cx.editor.theme.get("ui.popup");
            surface.clear_with(area, background);
            doc.render(area, surface, cx);
        }
    }
}