// markdown treesitter playground: https://ikatyang.github.io/tree-sitter-markdown/

use std::ops::Range;

use gpui::{AppContext, ParentElement, Refineable, RenderOnce, Styled, div, px, rems};
use tree_sitter::Node;

use crate::{app, theme};

const MARKDOWN_KIND_ID_SETEXT_H1_UNDERLINE: u16 = 8;
const MARKDOWN_KIND_ID_SETEXT_H2_UNDERLINE: u16 = 9;
const MARKDOWN_KIND_ID_ATX_H1_MARKER: u16 = 11;
const MARKDOWN_KIND_ID_ATX_H2_MARKER: u16 = 12;
const MARKDOWN_KIND_ID_ATX_H3_MARKER: u16 = 13;
const MARKDOWN_KIND_ID_ATX_H4_MARKER: u16 = 14;
const MARKDOWN_KIND_ID_ATX_H5_MARKER: u16 = 15;
const MARKDOWN_KIND_ID_ATX_H6_MARKER: u16 = 16;
const MARKDOWN_KIND_ID_LIST_MARKER: u16 = 48;
const MARKDOWN_KIND_ID_BACKSLASH_ESCAPE: u16 = 56;
const MARKDOWN_KIND_ID_CHARACTER_REFERENCE: u16 = 57;
const MARKDOWN_KIND_ID_TABLE_COLUMN_ALIGNMENT: u16 = 107;
const MARKDOWN_KIND_ID_HARD_LINE_BREAK: u16 = 110;
const MARKDOWN_KIND_ID_SOFT_LINE_BREAK: u16 = 111;
const MARKDOWN_KIND_ID_HTML_TAG_NAME: u16 = 117;
const MARKDOWN_KIND_ID_VIRTUAL_SPACE: u16 = 118;
const MARKDOWN_KIND_ID_DOCUMENT: u16 = 119;
const MARKDOWN_KIND_ID_THEMATIC_BREAK: u16 = 122;
const MARKDOWN_KIND_ID_PARAGRAPH: u16 = 124;
const MARKDOWN_KIND_ID_LINK_REFERENCE_DEFINITION: u16 = 126;
const MARKDOWN_KIND_ID_SETEXT_HEADING: u16 = 129;
const MARKDOWN_KIND_ID_ATX_HEADING: u16 = 132;
const MARKDOWN_KIND_ID_INDENTED_CODE_BLOCK: u16 = 134;
const MARKDOWN_KIND_ID_FENCED_CODE_BLOCK: u16 = 136;
const MARKDOWN_KIND_ID_CODE_FENCE_CONTENT: u16 = 138;
const MARKDOWN_KIND_ID_HTML_BLOCK_SCRIPT: u16 = 140;
const MARKDOWN_KIND_ID_HTML_BLOCK_COMMENT: u16 = 142;
const MARKDOWN_KIND_ID_HTML_BLOCK_PROCESSING: u16 = 144;
const MARKDOWN_KIND_ID_HTML_BLOCK_DECLARATION: u16 = 146;
const MARKDOWN_KIND_ID_HTML_BLOCK_CDATA: u16 = 148;
const MARKDOWN_KIND_ID_HTML_BLOCK_DIV: u16 = 150;
const MARKDOWN_KIND_ID_HTML_BLOCK_CMP: u16 = 152;
const MARKDOWN_KIND_ID_BLOCK_QUOTE: u16 = 154;
const MARKDOWN_KIND_ID_TIGHT_LIST: u16 = 156;
const MARKDOWN_KIND_ID_LOOSE_LIST: u16 = 158;
const MARKDOWN_KIND_ID_LIST_ITEM_TIGHT: u16 = 160;
const MARKDOWN_KIND_ID_TASK_LIST_ITEM_TIGHT: u16 = 161;
const MARKDOWN_KIND_ID_LIST_ITEM_LOOSE: u16 = 163;
const MARKDOWN_KIND_ID_TASK_LIST_ITEM_LOOSE: u16 = 164;
const MARKDOWN_KIND_ID_PARAGRAPH_TASK_LIST: u16 = 166;
const MARKDOWN_KIND_ID_SETEXT_HEADING_TASK_LIST: u16 = 168;
const MARKDOWN_KIND_ID_HEADING_CONTENT: u16 = 169;
const MARKDOWN_KIND_ID_TABLE: u16 = 170;
const MARKDOWN_KIND_ID_TABLE_HEADER_ROW: u16 = 172;
const MARKDOWN_KIND_ID_TABLE_DELIMITER_ROW: u16 = 174;
const MARKDOWN_KIND_ID_TABLE_DATA_ROW: u16 = 176;
const MARKDOWN_KIND_ID_EMPHASIS: u16 = 181;
const MARKDOWN_KIND_ID_STRONG_EMPHASIS: u16 = 182;
const MARKDOWN_KIND_ID_STRIKETHROUGH: u16 = 183;
const MARKDOWN_KIND_ID_LINK: u16 = 184;
const MARKDOWN_KIND_ID_IMAGE: u16 = 185;
const MARKDOWN_KIND_ID_LINK_DESTINATION: u16 = 190;
const MARKDOWN_KIND_ID_LINK_TITLE: u16 = 191;
const MARKDOWN_KIND_ID_WWW_AUTOLINK: u16 = 192;
const MARKDOWN_KIND_ID_URI_AUTOLINK_EXTENDED: u16 = 194;
const MARKDOWN_KIND_ID_EMAIL_AUTOLINK_EXTENDED: u16 = 196;
const MARKDOWN_KIND_ID_URI_AUTOLINK_ANGLE: u16 = 198;
const MARKDOWN_KIND_ID_EMAIL_AUTOLINK_ANGLE: u16 = 199;
const MARKDOWN_KIND_ID_CODE_SPAN: u16 = 200;
const MARKDOWN_KIND_ID_HTML_OPEN_TAG: u16 = 201;
const MARKDOWN_KIND_ID_HTML_SELF_CLOSING_TAG: u16 = 202;
const MARKDOWN_KIND_ID_HTML_CLOSE_TAG: u16 = 204;
const MARKDOWN_KIND_ID_HTML_COMMENT: u16 = 205;
const MARKDOWN_KIND_ID_HTML_PROCESSING_INSTRUCTION: u16 = 206;
const MARKDOWN_KIND_ID_HTML_DECLARATION: u16 = 207;
const MARKDOWN_KIND_ID_HTML_CDATA_SECTION: u16 = 208;
const MARKDOWN_KIND_ID_HTML_ATTRRIBUTE: u16 = 209;
const MARKDOWN_KIND_ID_HTML_ATTRIBUTE_VALUE: u16 = 210;
const MARKDOWN_KIND_ID_TEXT: u16 = 211;
const MARKDOWN_KIND_ID_HTML_ATTRIBUTE_KEY: u16 = 228;
const MARKDOWN_KIND_ID_HTML_DECLARATION_NAME: u16 = 229;
const MARKDOWN_KIND_ID_IMAGE_DESCRIPTION: u16 = 230;
const MARKDOWN_KIND_ID_INFO_STRING: u16 = 231;
const MARKDOWN_KIND_ID_LINE_BREAK: u16 = 232;
const MARKDOWN_KIND_ID_LINK_LABEL: u16 = 233;
const MARKDOWN_KIND_ID_LINK_TEXT: u16 = 234;
const MARKDOWN_KIND_ID_TABLE_CELL: u16 = 235;
const MARKDOWN_KIND_ID_TASK_LIST_ITEM_MARKER: u16 = 236;

pub(crate) struct MarkdownText {
    content: gpui::SharedString,
    blocks: Vec<ContentBlock>,
}

enum ContentBlock {
    Text {
        decoration: Option<&'static str>,
        text: gpui::SharedString,
        highlights: Vec<(Range<usize>, gpui::HighlightStyle)>,
        links: Vec<(Range<usize>, gpui::SharedString)>,
        style: gpui::StyleRefinement,
    },
}

pub(crate) fn new(
    content: gpui::SharedString,
    cx: &mut gpui::Context<MarkdownText>,
) -> MarkdownText {
    let mut view = MarkdownText {
        content,
        blocks: Vec::new(),
    };
    view.on_create(cx);
    view
}

impl Styled for ContentBlock {
    fn style(&mut self) -> &mut gpui::StyleRefinement {
        match self {
        | ContentBlock::Text { style, .. } => style,
        }
    }
}

impl MarkdownText {
    fn on_create(&mut self, cx: &gpui::Context<Self>) {
        let content = self.content.clone();
        let t = cx.background_spawn(async move {
            let mut parser = tree_sitter::Parser::new();
            parser
                .set_language(tree_sitter_markdown::language())
                .expect("tree-sitter-markdown language should load");
            parser.parse(content.as_str(), None)
        });

        cx.spawn(async |weak, cx| {
            if let Some(tree) = t.await {
                _ = weak.update(cx, |this, cx| {
                    let theme = app::current_theme(cx);
                    this.render_tree(&tree, &theme);
                    cx.notify();
                });
            };
        })
        .detach();
    }

    fn on_open_link(&self, _link: &str, _cx: &gpui::Context<Self>) {}

    fn render_tree(&mut self, tree: &tree_sitter::Tree, theme: &theme::Theme) {
        let mut cursor = tree.walk();
        cursor.goto_first_child();

        fn block_for_node(
            cursor: &mut tree_sitter::TreeCursor,
            content: &str,
            // byte_offset is the number of bytes to offset the content start byte by
            byte_offset: usize,
            theme: &theme::Theme,
        ) -> ContentBlock {
            let node_start_byte = cursor.node().start_byte();

            let mut highlights: Vec<(Range<usize>, gpui::HighlightStyle)> = Vec::new();
            let mut links: Vec<(Range<usize>, gpui::SharedString)> = Vec::new();

            cursor.goto_first_child();

            loop {
                let node = cursor.node();

                macro_rules! node_range {
                    () => {
                        (node.start_byte() - node_start_byte - byte_offset)
                            ..(node.end_byte() - node_start_byte - byte_offset)
                    };
                }

                match node.kind_id() {
                | MARKDOWN_KIND_ID_EMPHASIS => {
                    highlights.push((
                        node_range!(),
                        gpui::HighlightStyle {
                            font_style: Some(gpui::FontStyle::Italic),
                            ..Default::default()
                        },
                    ));
                }
                | MARKDOWN_KIND_ID_STRONG_EMPHASIS => highlights.push((
                    node_range!(),
                    gpui::HighlightStyle {
                        font_weight: Some(gpui::FontWeight::BOLD),
                        ..Default::default()
                    },
                )),

                | MARKDOWN_KIND_ID_LINK => {
                    if cursor.goto_first_child() {
                        highlights.push((
                            node_range!(),
                            gpui::HighlightStyle {
                                color: Some(theme.colors.accent.into()),
                                underline: Some(gpui::UnderlineStyle {
                                    color: Some(theme.colors.accent.into()),
                                    thickness: px(1.),
                                    wavy: false,
                                }),
                                ..Default::default()
                            },
                        ));

                        if cursor.goto_next_sibling()
                            && let Ok(src) = cursor.node().utf8_text(content.as_bytes())
                        {
                            links
                                .push((node_range!(), gpui::SharedString::from(String::from(src))));
                        } else {
                            // the link src is invalid, use an empty string as a fallback
                            // link on click handler will ignore empty string
                            links.push((node_range!(), "".into()))
                        }
                    }
                }

                | _ => {
                    // extend here to support more markdown node stylings
                }
                };

                if !cursor.goto_next_sibling() {
                    break;
                }
            }

            cursor.goto_parent();

            ContentBlock::Text {
                decoration: None,
                text: gpui::SharedString::new(
                    &content[(node_start_byte + byte_offset)..cursor.node().end_byte()],
                ),
                highlights: highlights,
                links: links,
                style: gpui::StyleRefinement::default(),
            }
        }

        loop {
            let current_node = cursor.node();

            fn render_fallback_content(
                cursor: &tree_sitter::TreeCursor,
                content: &str,
                blocks: &mut Vec<ContentBlock>,
            ) {
                blocks.push(ContentBlock::Text {
                    decoration: None,
                    text: gpui::SharedString::new(&content[cursor.node().byte_range()]),
                    highlights: Vec::new(),
                    links: Vec::new(),
                    style: gpui::StyleRefinement::default(),
                });
            }

            fn render_list_node(
                cursor: &mut tree_sitter::TreeCursor,
                content: &str,
                blocks: &mut Vec<ContentBlock>,
                theme: &theme::Theme,
                indentation: usize,
            ) -> bool {
                // expected tree shape for node pointed to by cursor:
                // tight_list
                //   list_item
                //     list_marker
                //     paragraph
                //     tight_list <-- recursive point

                // go to list_item node
                if !cursor.goto_first_child() {
                    render_fallback_content(&cursor, content, blocks);
                    return false;
                }

                let mut list_index = 0;

                loop {
                    if cursor.node().kind_id() != MARKDOWN_KIND_ID_LIST_ITEM_TIGHT
                        // if is list_item node, dive into list_marker node
                        || !cursor.goto_first_child()
                    {
                        // encountered non lists item node under tight list node
                        // dont know what to do, so skipping this node
                        if !cursor.goto_next_sibling() {
                            return false;
                        }
                        continue;
                    }

                    let marker_node = cursor.node();
                    let marker_content = &content[marker_node.byte_range()];

                    match marker_content {
                    // unordered list item
                    | "-" | "+" | "*" => {
                        // go to paragraph sibling node
                        let block = if cursor.goto_next_sibling() {
                            let mut b = block_for_node(cursor, content, 0, theme);
                            match b {
                            | ContentBlock::Text {
                                ref mut decoration, ..
                            } => *decoration = Some("•"),
                            }
                            b
                        } else {
                            ContentBlock::Text {
                                decoration: Some("•"),
                                text: gpui::SharedString::default(),
                                highlights: Vec::new(),
                                links: Vec::new(),
                                style: gpui::StyleRefinement::default(),
                            }
                        }
                        .text_sm()
                        .text_color(theme.colors.text)
                        .p(rems(indentation as f32));

                        blocks.push(block);

                        // if there is a nested tight_light after paragraph
                        // render it recursively
                        if cursor.goto_next_sibling()
                            && cursor.node().kind_id() == MARKDOWN_KIND_ID_TIGHT_LIST
                        {
                            render_list_node(cursor, content, blocks, theme, indentation + 1);
                        }
                    }

                    | _ => {
                        render_fallback_content(&cursor, content, blocks);
                        return false;
                    }
                    }

                    // go back to list_item node
                    cursor.goto_parent();

                    if !cursor.goto_next_sibling() {
                        // no more list_item in tight_list node
                        // go back up to tight_list node
                        cursor.goto_parent();
                        return true;
                    }
                }
            }

            match current_node.kind_id() {
            | MARKDOWN_KIND_ID_ATX_HEADING => {
                if !cursor.goto_first_child() {
                    render_fallback_content(&cursor, &self.content, &mut self.blocks);
                    continue;
                }

                let marker_node_kind = cursor.node().kind_id();

                let block = if cursor.goto_next_sibling()
                    && cursor.node().kind_id() == MARKDOWN_KIND_ID_HEADING_CONTENT
                {
                    // because HEADING_CONTENT node includes the space after the heading marker
                    // offset by 1 to exclude the space
                    block_for_node(&mut cursor, &self.content, 1, theme)
                } else {
                    ContentBlock::Text {
                        decoration: None,
                        text: gpui::SharedString::new(&self.content[current_node.byte_range()]),
                        highlights: Vec::new(),
                        links: Vec::new(),
                        style: gpui::StyleRefinement::default(),
                    }
                };

                let block = match marker_node_kind {
                | MARKDOWN_KIND_ID_ATX_H1_MARKER => block
                    .text_size(rems(2.25))
                    .font_weight(gpui::FontWeight::EXTRA_BOLD)
                    .mb_8(),
                | MARKDOWN_KIND_ID_ATX_H2_MARKER => block
                    .text_2xl()
                    .font_weight(gpui::FontWeight::BOLD)
                    .mt_12()
                    .mb_6(),
                | MARKDOWN_KIND_ID_ATX_H3_MARKER => block
                    .text_xl()
                    .font_weight(gpui::FontWeight::SEMIBOLD)
                    .mt_8()
                    .mb_3(),
                | MARKDOWN_KIND_ID_ATX_H4_MARKER => block
                    .text_base()
                    .font_weight(gpui::FontWeight::SEMIBOLD)
                    .mt_6()
                    .mb_2(),
                | _ => block,
                }
                .text_color(theme.colors.text);

                cursor.goto_parent();

                self.blocks.push(block);
            }

            | MARKDOWN_KIND_ID_PARAGRAPH => {
                let block = block_for_node(&mut cursor, &self.content, 0, theme)
                    .text_color(theme.colors.text)
                    .text_sm();

                self.blocks.push(block);
            }

            | MARKDOWN_KIND_ID_TIGHT_LIST => {
                let is_rendered =
                    render_list_node(&mut cursor, &self.content, &mut self.blocks, theme, 0);
                if !is_rendered {
                    continue;
                }
            }

            | _ => {
                println!(
                    "[WARN] formatting not implemenetd for node type {:?}",
                    current_node.kind()
                );

                let block = block_for_node(&mut cursor, &self.content, 0, theme)
                    .text_color(theme.colors.text)
                    .text_sm();

                self.blocks.push(block);
            }
            }

            if !cursor.goto_next_sibling() {
                break;
            }
        }
    }
}

impl gpui::Render for MarkdownText {
    fn render(
        &mut self,
        _window: &mut gpui::Window,
        cx: &mut gpui::prelude::Context<Self>,
    ) -> impl gpui::prelude::IntoElement {
        let theme = app::current_theme(cx);
        let children = self.blocks.iter().enumerate().map(|(i, block)| {
            match block {
            | ContentBlock::Text {
                decoration,
                text,
                highlights,
                links,
                style,
            } => {
                let styled_text =
                    gpui::StyledText::new(text.clone()).with_highlights(highlights.clone());

                let div = decoration
                    .map(|d| div().flex().flex_row().gap_2().items_start().child(d))
                    .unwrap_or_else(|| div());

                let mut div = if links.is_empty() {
                    // if no link in block, interactive text is not needed
                    div.child(styled_text)
                } else {
                    // if link in block, interactive text is needed
                    // to handle link clicks
                    let (link_ranges, srcs): (Vec<_>, Vec<_>) = links.iter().cloned().unzip();

                    let weak = cx.entity();
                    let t = gpui::InteractiveText::new(i, styled_text).on_click(
                        link_ranges,
                        move |i, _, cx| {
                            if let Some(src) = srcs.get(i) {
                                weak.update(cx, |this, cx| {
                                    this.on_open_link(src, cx);
                                    cx.notify();
                                })
                            }
                        },
                    );

                    div.child(t)
                };

                div.style().refine(&style);

                div
            }
            }
        });

        div().flex().flex_col().children(children)
    }
}