use crate::markdown_elements::{
    HeadingLevel, Link, ParsedMarkdown, ParsedMarkdownBlockQuote, ParsedMarkdownCodeBlock,
    ParsedMarkdownElement, ParsedMarkdownHeading, ParsedMarkdownList, ParsedMarkdownListItemType,
    ParsedMarkdownTable, ParsedMarkdownTableAlignment, ParsedMarkdownTableRow, ParsedMarkdownText,
};
use gpui::{
    div, px, rems, AbsoluteLength, AnyElement, DefiniteLength, Div, Element, ElementId,
    HighlightStyle, Hsla, InteractiveText, IntoElement, ParentElement, SharedString, Styled,
    StyledText, TextStyle, WeakView, WindowContext,
};
use std::{
    ops::{Mul, Range},
    sync::Arc,
};
use theme::{ActiveTheme, SyntaxTheme};
use ui::{h_flex, v_flex, Label};
use workspace::Workspace;

pub struct RenderContext {
    workspace: Option<WeakView<Workspace>>,
    next_id: usize,
    text_style: TextStyle,
    border_color: Hsla,
    text_color: Hsla,
    text_muted_color: Hsla,
    code_block_background_color: Hsla,
    code_span_background_color: Hsla,
    syntax_theme: Arc<SyntaxTheme>,
    indent: usize,
}

impl RenderContext {
    pub fn new(workspace: Option<WeakView<Workspace>>, cx: &WindowContext) -> RenderContext {
        let theme = cx.theme().clone();

        RenderContext {
            workspace,
            next_id: 0,
            indent: 0,
            text_style: cx.text_style(),
            syntax_theme: theme.syntax().clone(),
            border_color: theme.colors().border,
            text_color: theme.colors().text,
            text_muted_color: theme.colors().text_muted,
            code_block_background_color: theme.colors().surface_background,
            code_span_background_color: theme.colors().editor_document_highlight_read_background,
        }
    }

    fn next_id(&mut self, span: &Range<usize>) -> ElementId {
        let id = format!("markdown-{}-{}-{}", self.next_id, span.start, span.end);
        self.next_id += 1;
        ElementId::from(SharedString::from(id))
    }

    /// This ensures that children inside of block quotes
    /// have padding between them.
    ///
    /// For example, for this markdown:
    ///
    /// ```markdown
    /// > This is a block quote.
    /// >
    /// > And this is the next paragraph.
    /// ```
    ///
    /// We give padding between "This is a block quote."
    /// and "And this is the next paragraph."
    fn with_common_p(&self, element: Div) -> Div {
        if self.indent > 0 {
            element.pb_3()
        } else {
            element
        }
    }
}

pub fn render_parsed_markdown(
    parsed: &ParsedMarkdown,
    workspace: Option<WeakView<Workspace>>,
    cx: &WindowContext,
) -> Vec<AnyElement> {
    let mut cx = RenderContext::new(workspace, cx);
    let mut elements = Vec::new();

    for child in &parsed.children {
        elements.push(render_markdown_block(child, &mut cx));
    }

    return elements;
}

pub fn render_markdown_block(block: &ParsedMarkdownElement, cx: &mut RenderContext) -> AnyElement {
    use ParsedMarkdownElement::*;
    match block {
        Paragraph(text) => render_markdown_paragraph(text, cx),
        Heading(heading) => render_markdown_heading(heading, cx),
        List(list) => render_markdown_list(list, cx),
        Table(table) => render_markdown_table(table, cx),
        BlockQuote(block_quote) => render_markdown_block_quote(block_quote, cx),
        CodeBlock(code_block) => render_markdown_code_block(code_block, cx),
        HorizontalRule(_) => render_markdown_rule(cx),
    }
}

fn render_markdown_heading(parsed: &ParsedMarkdownHeading, cx: &mut RenderContext) -> AnyElement {
    let size = match parsed.level {
        HeadingLevel::H1 => rems(2.),
        HeadingLevel::H2 => rems(1.5),
        HeadingLevel::H3 => rems(1.25),
        HeadingLevel::H4 => rems(1.),
        HeadingLevel::H5 => rems(0.875),
        HeadingLevel::H6 => rems(0.85),
    };

    let color = match parsed.level {
        HeadingLevel::H6 => cx.text_muted_color,
        _ => cx.text_color,
    };

    let line_height = DefiniteLength::from(size.mul(1.25));

    div()
        .line_height(line_height)
        .text_size(size)
        .text_color(color)
        .pt(rems(0.15))
        .pb_1()
        .child(render_markdown_text(&parsed.contents, cx))
        .whitespace_normal()
        .into_any()
}

fn render_markdown_list(parsed: &ParsedMarkdownList, cx: &mut RenderContext) -> AnyElement {
    use ParsedMarkdownListItemType::*;

    let mut items = vec![];
    for item in &parsed.children {
        let padding = rems((item.depth - 1) as f32 * 0.25);

        let bullet = match item.item_type {
            Ordered(order) => format!("{}.", order),
            Unordered => "•".to_string(),
            Task(checked) => if checked { "☑" } else { "☐" }.to_string(),
        };
        let bullet = div().mr_2().child(Label::new(bullet));

        let contents: Vec<AnyElement> = item
            .contents
            .iter()
            .map(|c| render_markdown_block(c.as_ref(), cx))
            .collect();

        let item = h_flex()
            .pl(DefiniteLength::Absolute(AbsoluteLength::Rems(padding)))
            .items_start()
            .children(vec![bullet, div().children(contents).pr_4().w_full()]);

        items.push(item);
    }

    cx.with_common_p(div()).children(items).into_any()
}

fn render_markdown_table(parsed: &ParsedMarkdownTable, cx: &mut RenderContext) -> AnyElement {
    let header = render_markdown_table_row(&parsed.header, &parsed.column_alignments, true, cx);

    let body: Vec<AnyElement> = parsed
        .body
        .iter()
        .map(|row| render_markdown_table_row(row, &parsed.column_alignments, false, cx))
        .collect();

    cx.with_common_p(v_flex())
        .w_full()
        .child(header)
        .children(body)
        .into_any()
}

fn render_markdown_table_row(
    parsed: &ParsedMarkdownTableRow,
    alignments: &Vec<ParsedMarkdownTableAlignment>,
    is_header: bool,
    cx: &mut RenderContext,
) -> AnyElement {
    let mut items = vec![];

    for cell in &parsed.children {
        let alignment = alignments
            .get(items.len())
            .copied()
            .unwrap_or(ParsedMarkdownTableAlignment::None);

        let contents = render_markdown_text(cell, cx);

        let container = match alignment {
            ParsedMarkdownTableAlignment::Left | ParsedMarkdownTableAlignment::None => div(),
            ParsedMarkdownTableAlignment::Center => v_flex().items_center(),
            ParsedMarkdownTableAlignment::Right => v_flex().items_end(),
        };

        let mut cell = container
            .w_full()
            .child(contents)
            .px_2()
            .py_1()
            .border_color(cx.border_color);

        if is_header {
            cell = cell.border_2()
        } else {
            cell = cell.border_1()
        }

        items.push(cell);
    }

    h_flex().children(items).into_any_element()
}

fn render_markdown_block_quote(
    parsed: &ParsedMarkdownBlockQuote,
    cx: &mut RenderContext,
) -> AnyElement {
    cx.indent += 1;

    let children: Vec<AnyElement> = parsed
        .children
        .iter()
        .map(|child| render_markdown_block(child, cx))
        .collect();

    cx.indent -= 1;

    cx.with_common_p(div())
        .child(
            div()
                .border_l_4()
                .border_color(cx.border_color)
                .pl_3()
                .children(children),
        )
        .into_any()
}

fn render_markdown_code_block(
    parsed: &ParsedMarkdownCodeBlock,
    cx: &mut RenderContext,
) -> AnyElement {
    cx.with_common_p(div())
        .px_3()
        .py_3()
        .bg(cx.code_block_background_color)
        .child(StyledText::new(parsed.contents.clone()))
        .into_any()
}

fn render_markdown_paragraph(parsed: &ParsedMarkdownText, cx: &mut RenderContext) -> AnyElement {
    cx.with_common_p(div())
        .child(render_markdown_text(parsed, cx))
        .into_any_element()
}

fn render_markdown_text(parsed: &ParsedMarkdownText, cx: &mut RenderContext) -> AnyElement {
    let element_id = cx.next_id(&parsed.source_range);

    let highlights = gpui::combine_highlights(
        parsed.highlights.iter().filter_map(|(range, highlight)| {
            let highlight = highlight.to_highlight_style(&cx.syntax_theme)?;
            Some((range.clone(), highlight))
        }),
        parsed
            .regions
            .iter()
            .zip(&parsed.region_ranges)
            .filter_map(|(region, range)| {
                if region.code {
                    Some((
                        range.clone(),
                        HighlightStyle {
                            background_color: Some(cx.code_span_background_color),
                            ..Default::default()
                        },
                    ))
                } else {
                    None
                }
            }),
    );

    let mut links = Vec::new();
    let mut link_ranges = Vec::new();
    for (range, region) in parsed.region_ranges.iter().zip(&parsed.regions) {
        if let Some(link) = region.link.clone() {
            links.push(link);
            link_ranges.push(range.clone());
        }
    }

    let workspace = cx.workspace.clone();

    InteractiveText::new(
        element_id,
        StyledText::new(parsed.contents.clone()).with_highlights(&cx.text_style, highlights),
    )
    .on_click(
        link_ranges,
        move |clicked_range_ix, window_cx| match &links[clicked_range_ix] {
            Link::Web { url } => window_cx.open_url(url),
            Link::Path { path } => {
                if let Some(workspace) = &workspace {
                    _ = workspace.update(window_cx, |workspace, cx| {
                        workspace.open_abs_path(path.clone(), false, cx).detach();
                    });
                }
            }
        },
    )
    .into_any_element()
}

fn render_markdown_rule(cx: &mut RenderContext) -> AnyElement {
    let rule = div().w_full().h(px(2.)).bg(cx.border_color);
    div().pt_3().pb_3().child(rule).into_any()
}