use helix_core::{
    syntax::RopeProvider,
    text_annotations::TextAnnotations,
    tree_sitter::{QueryCursor, QueryMatch},
    visual_offset_from_block, Position,
};
use helix_view::{Document, Theme, View};

use tui::buffer::Buffer as Surface;

use super::{
    document::{render_text, LineDecoration, TextRenderer, TranslatedPosition},
    EditorView,
};

#[derive(Debug, Clone)]
pub struct StickyNode {
    line: usize,
    visual_line: u16,
    byte_range: std::ops::Range<usize>,
    indicator: Option<String>,
    anchor: usize,
    has_context_end: bool,
}

fn get_context_paired_range(
    query_match: &QueryMatch,
    start_index: u32,
    end_index: u32,
    top_first_byte: usize,
    last_scan_byte: usize,
) -> Option<std::ops::Range<usize>> {
    // get all the captured @context.params nodes
    let end_nodes = once_cell::unsync::Lazy::new(|| {
        query_match
            .nodes_for_capture_index(end_index)
            .collect::<Vec<_>>()
    });

    query_match
        .nodes_for_capture_index(start_index)
        .find_map(|context| {
            let ctx_start_range = context.byte_range();

            // filter all matches that are out of scope, based on follows-cursor
            let start_range_contains_bytes = ctx_start_range.contains(&top_first_byte)
                && ctx_start_range.contains(&last_scan_byte);
            if !start_range_contains_bytes {
                return None;
            }

            let ctx_start_row = context.start_position().row;
            let ctx_start_byte = ctx_start_range.start;

            end_nodes.iter().find_map(|it| {
                let end = it.end_byte();
                // check whether or not @context.params nodes are on different lines
                (ctx_start_row != it.end_position().row && ctx_start_range.contains(&end))
                    .then_some(ctx_start_byte..end.saturating_sub(1))
            })
        })
}

/// Calculates the sticky nodes
pub fn calculate_sticky_nodes(
    nodes: &Option<Vec<StickyNode>>,
    doc: &Document,
    view: &View,
    config: &helix_view::editor::Config,
    cursor_cache: &Option<Option<Position>>,
) -> Option<Vec<StickyNode>> {
    let cursor_cache = cursor_cache.expect("cursor is cached")?;

    let syntax = doc.syntax()?;
    let tree = syntax.tree();
    let text = doc.text().slice(..);
    let viewport = view.inner_area(doc);
    let cursor_byte = text.char_to_byte(doc.selection(view.id).primary().cursor(text));

    let anchor_line = text.char_to_line(view.offset.anchor);
    let visual_cursor_row = anchor_line.saturating_sub(cursor_cache.row);

    if visual_cursor_row == 0 {
        return None;
    }

    let top_first_byte =
        text.line_to_byte(anchor_line + nodes.as_ref().map_or(0, |nodes| nodes.len()));

    let last_scan_byte = if config.sticky_context.follow_cursor {
        cursor_byte
    } else {
        top_first_byte
    };

    // nothing has changed, so the cached result can be returned
    if let Some(nodes) = nodes {
        if nodes.iter().any(|node| view.offset.anchor == node.anchor) {
            return Some(
                nodes
                    .iter()
                    .take(visual_cursor_row as usize)
                    .cloned()
                    .collect(),
            );
        }
    }

    let context_nodes = doc
        .language_config()
        .and_then(|lang| lang.context_query())?;

    let start_index = context_nodes.query.capture_index_for_name("context")?;
    let end_index = context_nodes
        .query
        .capture_index_for_name("context.params")
        .unwrap_or(start_index);

    // result is list of numbers of lines that should be rendered in the LSP context
    let mut result: Vec<StickyNode> = Vec::new();

    let mut cursor = QueryCursor::new();

    // only run the query from start to the cursor location
    cursor.set_byte_range(0..last_scan_byte);
    let query = &context_nodes.query;
    let query_nodes = cursor.matches(query, tree.root_node(), RopeProvider(text));

    for matched_node in query_nodes {
        // find @context.params nodes
        let node_byte_range = get_context_paired_range(
            &matched_node,
            start_index,
            end_index,
            top_first_byte,
            last_scan_byte,
        );

        for node in matched_node.nodes_for_capture_index(start_index) {
            if (!node.byte_range().contains(&last_scan_byte)
                || !node.byte_range().contains(&top_first_byte))
                && node.start_position().row != anchor_line + result.len()
                && node_byte_range.is_none()
            {
                continue;
            }

            result.push(StickyNode {
                line: node.start_position().row,
                visual_line: 0,
                byte_range: node_byte_range
                    .as_ref()
                    .unwrap_or(&(node.start_byte()..node.start_byte()))
                    .clone(),
                indicator: None,
                anchor: view.offset.anchor,
                has_context_end: node_byte_range.is_some(),
            });
        }
    }
    // result should be filled by now
    if result.is_empty() {
        return None;
    }

    // Order of commands is important here
    result.sort_unstable_by(|lhs, rhs| lhs.line.cmp(&rhs.line));
    result.dedup_by(|lhs, rhs| lhs.line == rhs.line);

    // always cap the maximum amount of sticky contextes to 1/3 of the viewport
    // unless configured otherwise
    let max_lines = config.sticky_context.max_lines as u16;
    let max_nodes_amount = max_lines.min(viewport.height / 3) as usize;

    let skip = result.len().saturating_sub(max_nodes_amount);

    result = result
        .iter()
        // only take the nodes until 1 / 3 of the viewport is reached or the maximum amount of sticky nodes
        .skip(skip)
        .enumerate()
        .take_while(|(i, _)| {
            *i + Into::<usize>::into(config.sticky_context.indicator) != visual_cursor_row as usize
        }) // also only nodes that don't overlap with the visual cursor position
        .map(|(i, node)| {
            let mut new_node = node.clone();
            new_node.visual_line = i as u16;
            new_node
        })
        .collect();

    if config.sticky_context.indicator {
        let str = "─".repeat(viewport.width as usize);

        result.push(StickyNode {
            line: usize::MAX,
            visual_line: result.len() as u16,
            byte_range: 0..0,
            indicator: Some(str),
            anchor: view.offset.anchor,
            has_context_end: false,
        });
    }

    Some(result)
}

/// Render the sticky context
pub fn render_sticky_context(
    doc: &Document,
    view: &View,
    surface: &mut Surface,
    context: &Option<Vec<StickyNode>>,
    line_decoration: &mut [Box<dyn LineDecoration + '_>],
    translated_positions: &mut [TranslatedPosition],
    theme: &Theme,
) {
    let Some(context) = context else {
            return;
        };

    let text = doc.text().slice(..);
    let viewport = view.inner_area(doc);

    // backup (status line) shall always exist
    let status_line_style = theme
        .try_get("ui.statusline.context")
        .expect("`ui.statusline.context` exists");

    // define sticky context styles
    let context_style = theme
        .try_get("ui.sticky.context")
        .unwrap_or(status_line_style);
    let indicator_style = theme
        .try_get("ui.sticky.indicator")
        .unwrap_or(status_line_style);

    let mut context_area = viewport;
    context_area.height = 1;

    for node in context {
        surface.clear_with(context_area, context_style);

        let mut new_offset = view.offset;
        let mut line_context_area = context_area;

        if let Some(indicator) = node.indicator.as_deref() {
            // set the indicator
            surface.set_stringn(
                line_context_area.x,
                line_context_area.y,
                indicator,
                indicator.len(),
                indicator_style,
            );
            continue;
        }

        // get the len of bytes of the text that will be written (the "definition" line)
        let line = text.line(node.line);
        let already_written = line.len_bytes() as u16;
        let dots = "...";

        let virtual_text_annotations = TextAnnotations::default();

        // if the definition of the function contains multiple lines
        if node.has_context_end {
            let (whitespace_offset, _) = visual_offset_from_block(
                text,
                text.line_to_byte(text.byte_to_line(node.byte_range.end)),
                node.byte_range.end,
                &helix_core::doc_formatter::TextFormat::default(),
                &TextAnnotations::default(),
            );
            let whitespace_offset = whitespace_offset.col as u16 + 1;
            // calculation of the correct space on where the end of the signature
            // should be drawn at
            let mut additional_area = line_context_area;
            additional_area.x +=
                (already_written + dots.len() as u16).saturating_sub(whitespace_offset);

            // render the end of the function definition
            let mut renderer = TextRenderer::new(
                surface,
                doc,
                theme,
                view.offset.horizontal_offset,
                additional_area,
            );

            new_offset.anchor = text.byte_to_char(node.byte_range.end);
            let highlights = EditorView::doc_syntax_highlights(doc, new_offset.anchor, 1, theme);

            let mut text_format = doc.text_format(additional_area.width, Some(theme));
            text_format.soft_wrap = false;

            render_text(
                &mut renderer,
                text,
                new_offset,
                &text_format,
                &virtual_text_annotations,
                highlights,
                theme,
                line_decoration,
                translated_positions,
            );

            // draw the "..." with the keyword.operator style
            let new_x_location =
                (already_written + line_context_area.x).saturating_sub(match doc.line_ending {
                    helix_core::LineEnding::Crlf => 2,
                    helix_core::LineEnding::LF => 1,
                });

            surface.set_stringn(
                new_x_location,
                additional_area.y,
                dots,
                dots.len(),
                theme.get("keyword.operator"),
            );
        }

        new_offset.anchor = text.byte_to_char(node.byte_range.start);

        // get all highlights from the latest point
        let highlights = EditorView::doc_syntax_highlights(doc, new_offset.anchor, 1, theme);

        let mut renderer = TextRenderer::new(
            surface,
            doc,
            theme,
            view.offset.horizontal_offset,
            line_context_area,
        );

        // limit the width to its size - 1, so that it won't draw trailing whitespace characters
        line_context_area.width = already_written - 1;

        let mut text_format = doc.text_format(line_context_area.width, Some(theme));
        text_format.soft_wrap = false;

        render_text(
            &mut renderer,
            text,
            new_offset,
            &text_format,
            &virtual_text_annotations,
            highlights,
            theme,
            line_decoration,
            translated_positions,
        );

        // next node
        context_area.y += 1;
    }
}