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

use std::sync::{Arc, LazyLock};

use gpui::{AppContext, FontWeight, ParentElement, Styled, div, relative, rems};

use crate::{
    app,
    component::rich_text::{RichText, RichTextContent, RichTextContentBuilder, rich_text},
    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: Arc<str>,
    blocks: Vec<ContentBlock>,
}

enum ContentBlock {
    Heading {
        font_size: gpui::Rems,
        font_weight: gpui::FontWeight,
        mt: gpui::Rems,
        mb: gpui::Rems,
        content: RichTextContent,
    },
    Code {
        content: gpui::SharedString,
    },
    Paragraph {
        decoration: Option<String>,
        content: RichTextContent,
    },
    Empty,
    Table {
        row_count: usize,
        col_count: usize,
        cells: Vec<RichTextContent>,
    },
}

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

impl MarkdownText {
    fn on_create(&mut self, cx: &gpui::Context<Self>) {
        let content = Arc::clone(&self.content);
        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_bytes(), 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) {
        static ORDERED_LIST_MARKER_REGEX: LazyLock<regex::Regex> =
            LazyLock::new(|| regex::Regex::new(r"^\d+\.$").unwrap());

        let mut cursor = tree.walk();
        cursor.goto_first_child();

        let mut is_first_heading = true;

        fn build_rich_text_for_node(
            cursor: &mut tree_sitter::TreeCursor,
            builder: &mut RichTextContentBuilder,
            content: &str,
            // byte_offset is the number of bytes to offset the content start byte by
            byte_offset: usize,
            theme: &theme::Theme,
            parent_style: Option<gpui::HighlightStyle>,
        ) {
            let node_start_byte = cursor.node().start_byte();

            let style = parent_style.unwrap_or_default();

            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_TEXT => {
                    println!(
                        "current node start byte {} parent node start byte {}",
                        node.start_byte(),
                        node_start_byte
                    );
                    if let Some(t) = node.utf8_text(content.as_ref()).ok() {
                        builder.push_text(t, style);
                    }
                }

                | MARKDOWN_KIND_ID_EMPHASIS => {
                    build_rich_text_for_node(
                        cursor,
                        builder,
                        content,
                        byte_offset,
                        theme,
                        Some(gpui::HighlightStyle {
                            font_style: Some(gpui::FontStyle::Italic),
                            ..style
                        }),
                    );
                }

                | MARKDOWN_KIND_ID_STRONG_EMPHASIS => {
                    build_rich_text_for_node(
                        cursor,
                        builder,
                        content,
                        byte_offset,
                        theme,
                        Some(gpui::HighlightStyle {
                            font_weight: Some(gpui::FontWeight::BOLD),
                            ..style
                        }),
                    );
                }

                | MARKDOWN_KIND_ID_LINK => {
                    cursor.goto_first_child();

                    let (description, src) =
                        if cursor.node().kind_id() == MARKDOWN_KIND_ID_LINK_DESTINATION {
                            let node = cursor.node();
                            let src = &content[node_range!()];
                            (src, src)
                        } else {
                            let node = cursor.node();
                            let description = &content[node_range!()];
                            if cursor.goto_next_sibling() {
                                debug_assert!(
                                    cursor.node().kind_id() == MARKDOWN_KIND_ID_LINK_DESTINATION
                                );
                                let node = cursor.node();
                                (description, &content[node_range!()])
                            } else {
                                // no src for this link node
                                (description, "")
                            }
                        };

                    builder.push_link(description, src.to_owned());

                    cursor.goto_parent();
                }

                | _ => {
                    // extend here to support more styles
                }
                };

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

            cursor.goto_parent();
        }

        loop {
            let current_node = cursor.node();

            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
                cursor.goto_first_child();

                let mut list_index: Option<usize> = None;

                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()];

                    let list_marker_char = match marker_content {
                    // unordered list item
                    | "-" | "+" | "*" => "•".to_string(),

                    | marker_content if ORDERED_LIST_MARKER_REGEX.is_match(marker_content) => {
                        let i = list_index.get_or_insert_with(|| {
                            marker_content
                                .strip_suffix('.')
                                .unwrap()
                                .parse::<usize>()
                                .unwrap()
                        });
                        let j = *i;
                        *i = j + 1;
                        format!("{j}.")
                    }

                    | _ => "•".to_string(),
                    };

                    // go to paragraph sibling node
                    let block = if cursor.goto_next_sibling() {
                        let mut builder = RichTextContentBuilder::new();
                        build_rich_text_for_node(cursor, &mut builder, content, 0, theme, None);
                        ContentBlock::Paragraph {
                            decoration: Some(list_marker_char.clone()),
                            content: builder.build(),
                        }
                    } else {
                        // empty block
                        ContentBlock::Empty
                    };

                    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);
                    }

                    // 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 => {
                cursor.goto_first_child();

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

                let Some(content) = (if cursor.goto_next_sibling()
                    && cursor.node().kind_id() == MARKDOWN_KIND_ID_HEADING_CONTENT
                {
                    let mut builder = RichTextContentBuilder::new();
                    // because HEADING_CONTENT node includes the space after the heading marker
                    // offset by 1 to exclude the space
                    build_rich_text_for_node(
                        &mut cursor,
                        &mut builder,
                        &self.content,
                        1,
                        theme,
                        None,
                    );
                    Some(builder.build())
                } else {
                    None
                }) else {
                    continue;
                };

                let mut block = match marker_node_kind {
                | MARKDOWN_KIND_ID_ATX_H1_MARKER => ContentBlock::Heading {
                    font_size: rems(2.25),
                    font_weight: gpui::FontWeight::EXTRA_BOLD,
                    mt: rems(0.),
                    mb: rems(1.5),
                    content,
                },
                | MARKDOWN_KIND_ID_ATX_H2_MARKER => ContentBlock::Heading {
                    font_size: rems(1.5),
                    font_weight: gpui::FontWeight::BOLD,
                    mt: rems(1.5),
                    mb: rems(1.),
                    content,
                },
                | MARKDOWN_KIND_ID_ATX_H3_MARKER => ContentBlock::Heading {
                    font_size: rems(1.25),
                    font_weight: gpui::FontWeight::SEMIBOLD,
                    mt: rems(2.),
                    mb: rems(0.75),
                    content,
                },
                | MARKDOWN_KIND_ID_ATX_H4_MARKER => ContentBlock::Heading {
                    font_size: rems(1.),
                    font_weight: FontWeight::SEMIBOLD,
                    mt: rems(1.5),
                    mb: rems(0.5),
                    content,
                },
                | MARKDOWN_KIND_ID_ATX_H5_MARKER | MARKDOWN_KIND_ID_ATX_H6_MARKER | _ => {
                    ContentBlock::Heading {
                        font_size: rems(1.),
                        font_weight: FontWeight::NORMAL,
                        mt: rems(1.5),
                        mb: rems(0.5),
                        content,
                    }
                }
                };

                if is_first_heading {
                    is_first_heading = false;
                }

                cursor.goto_parent();

                self.blocks.push(block);
            }

            | MARKDOWN_KIND_ID_PARAGRAPH => {
                let mut builder = RichTextContentBuilder::new();
                // because HEADING_CONTENT node includes the space after the heading marker
                // offset by 1 to exclude the space
                build_rich_text_for_node(&mut cursor, &mut builder, &self.content, 0, theme, None);
                self.blocks.push(ContentBlock::Paragraph {
                    decoration: None,
                    content: builder.build(),
                });
            }

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

            | MARKDOWN_KIND_ID_FENCED_CODE_BLOCK => {
                // expected tree shape:
                // fenced_code_block
                // ├── info_string? (present if there is a language annotation)
                // └── code_fence_content? (present if there is some content between the backticks)

                if !cursor.goto_first_child() {
                    self.blocks.push(ContentBlock::Empty);
                    continue;
                }

                let content = if cursor.node().kind_id() == MARKDOWN_KIND_ID_INFO_STRING {
                    // skipping info string (which annotates the code block)
                    if cursor.goto_next_sibling() {
                        // this is code_fence_content node
                        gpui::SharedString::new(
                            cursor
                                .node()
                                .utf8_text(self.content.as_bytes())
                                .unwrap_or_default(),
                        )
                    } else {
                        gpui::SharedString::default()
                    }
                } else {
                    // assuming the current node is already code_fence_content
                    gpui::SharedString::new(
                        cursor
                            .node()
                            .utf8_text(self.content.as_bytes())
                            .unwrap_or_default(),
                    )
                };

                cursor.goto_parent();

                self.blocks.push(ContentBlock::Code { content });
            }

            // | MARKDOWN_KIND_ID_TABLE => {
            //     cursor.goto_first_child();
            //     debug_assert!(cursor.node().kind_id() == MARKDOWN_KIND_ID_TABLE_HEADER_ROW);

            //     let col_count = cursor.node().child_count();
            //     // markdown tables aren't usually that big
            //     // lets assume the average markdown table has 10 rows (inc header)
            //     // preallocate the vec with capacity row * col, should be big enough to avoid realloc
            //     let min_row_count = 10;

            //     // cell text blocks are stored in row-major order
            //     let cell_blocks: Vec<ContentBlock> = Vec::with_capacity(col_count * min_row_count);

            //     cursor.goto_first_child();
            //     debug_assert!(cursor.node().kind_id() == MARKDOWN_KIND_ID_TABLE_CELL);

            //     loop {
            //         let cell_node = cursor.node();
            //         let cell_text_block = rich_text_for_node(&mut cursor, &self.content, 1, theme);
            //         cell_blocks.push(ContentBlock::Paragraph(cell_text_block));

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

                let mut builder = RichTextContentBuilder::new();
                build_rich_text_for_node(&mut cursor, &mut builder, &self.content, 0, theme, None);

                self.blocks.push(ContentBlock::Paragraph {
                    decoration: None,
                    content: builder.build(),
                });
            }
            }

            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::Heading {
                font_size,
                font_weight,
                mt,
                mb,
                content,
            } => div()
                .min_w_0()
                .mt(gpui::Length::from(*mt))
                .mb(gpui::Length::from(*mb))
                .text_size(gpui::AbsoluteLength::from(*font_size))
                .font_weight(*font_weight)
                .child(rich_text(content.clone())),

            | ContentBlock::Paragraph {
                decoration,
                content,
            } => match decoration {
            | None => div().min_w_0().child(rich_text(content.clone())),
            | Some(decoration) => div()
                .w_full()
                .flex()
                .flex_row()
                .gap_2()
                .items_start()
                .text_color(theme.colors.text)
                .child(decoration.clone())
                .child(div().flex_1().min_w_0().child(rich_text(content.clone()))),
            },

            | ContentBlock::Code { content } => div()
                .min_w_0()
                .w_full()
                .text_sm()
                .text_color(theme.colors.text)
                .line_height(relative(1.2))
                .font_family("Menlo")
                .px_3()
                .py_2()
                .rounded_sm()
                .bg(theme.colors.code_bg)
                .border_1()
                .my_4()
                .border_color(theme.colors.code_border)
                .child(content.clone()),

            | ContentBlock::Table {
                row_count,
                col_count,
                cells,
            } => div(),

            | ContentBlock::Empty => div(),
            });

        div().w_full().children(children)
    }
}