use std::cell::RefCell;
use std::rc::Rc;

use gpui::{
    AppContext as _, Context, Entity, IntoElement, MouseButton, MouseDownEvent, MouseUpEvent,
    ParentElement as _, Render, Styled as _, TestAppContext, VisualTestContext, Window, div, point,
    px,
};
use gpui_native_editor::highlight::Role;
use gpui_native_editor::markdown::{
    InlineSpan, InlineStyle, ListMarker, MarkdownBlock, MarkdownHeading, MarkdownViewState,
};

fn spans_text(spans: &[InlineSpan]) -> String {
    spans
        .iter()
        .map(|span| span.text.as_ref())
        .collect::<Vec<_>>()
        .join("")
}

fn paragraph_of(blocks: &[MarkdownBlock], index: usize) -> (&Vec<InlineSpan>, usize, bool) {
    match &blocks[index] {
        MarkdownBlock::Paragraph {
            spans,
            indent,
            quote,
        } => (spans, *indent, *quote),
        other => panic!("block {index} is {other:?}, not a paragraph"),
    }
}

fn item_of(blocks: &[MarkdownBlock], index: usize) -> (ListMarker, String, usize, bool) {
    match &blocks[index] {
        MarkdownBlock::ListItem {
            marker,
            spans,
            indent,
            quote,
        } => (*marker, spans_text(spans), *indent, *quote),
        other => panic!("block {index} is {other:?}, not a list item"),
    }
}

#[test]
fn inline_styles_survive_nesting_and_merge_runs() {
    let blocks = parse_body("a **bold *both* b** `code` [link](https://example.com) done");
    assert_eq!(blocks.len(), 1);
    let (spans, ..) = paragraph_of(&blocks, 0);

    let styled: Vec<(String, &InlineStyle)> = spans
        .iter()
        .map(|span| (span.text.to_string(), &span.style))
        .collect();

    assert!(styled.contains(&("bold ".to_string(), &InlineStyle::Strong)));
    assert!(
        styled.contains(&("both".to_string(), &InlineStyle::StrongEmphasis)),
        "strong wrapping emphasis combines into one style"
    );
    assert!(styled.contains(&(" b".to_string(), &InlineStyle::Strong)));
    assert!(styled.contains(&("code".to_string(), &InlineStyle::Code)));
    assert!(styled.contains(&(
        "link".to_string(),
        &InlineStyle::Link {
            destination: "https://example.com".into()
        }
    )));
    assert!(styled.contains(&("a ".to_string(), &InlineStyle::Text)));
    assert!(styled.contains(&(" done".to_string(), &InlineStyle::Text)));
}

#[test]
fn headings_headings_and_thematic_breaks_parse() {
    let blocks = parse_body("# Title\n\ntext\n\n---\n\n###### small");
    assert_eq!(blocks.len(), 4);
    assert!(matches!(
        &blocks[0],
        MarkdownBlock::Heading {
            level: MarkdownHeading::H1,
            ..
        }
    ));
    assert!(matches!(&blocks[2], MarkdownBlock::ThematicBreak { .. }));
    assert!(matches!(
        &blocks[3],
        MarkdownBlock::Heading {
            level: MarkdownHeading::H6,
            ..
        }
    ));
}

#[test]
fn lists_number_order_and_nest() {
    let source = "- one\n- two\n  1. inner\n  2. more\n3. third\n";
    let blocks = parse_body(source);

    let markers: Vec<ListMarker> = blocks
        .iter()
        .filter_map(|block| match block {
            MarkdownBlock::ListItem { marker, .. } => Some(*marker),
            _ => None,
        })
        .collect();
    assert_eq!(
        markers,
        vec![
            ListMarker::Bullet,
            ListMarker::Bullet,
            ListMarker::Ordered(1),
            ListMarker::Ordered(2),
            ListMarker::Ordered(3),
        ],
        "ordered numbering continues across nested lists"
    );

    let (_, _, outer_indent, _) = item_of(&blocks, 0);
    assert_eq!(outer_indent, 0);
    let (_, _, inner_indent, _) = item_of(&blocks, 2);
    assert_eq!(inner_indent, 1, "nested items indent one level deeper");
}

#[test]
fn tight_items_stay_tight_but_block_content_flushes_before_them() {
    let source = "- item text\n\n  second paragraph\n- next\n";
    let blocks = parse_body(source);

    // The first paragraph of a loose item carries its marker row; the
    // continuation flushes as a plain paragraph at the same indent.
    let (marker, text, indent, _) = item_of(&blocks, 0);
    assert_eq!(marker, ListMarker::Bullet);
    assert_eq!(text, "item text");
    assert_eq!(indent, 0);

    let (spans, indent, _) = paragraph_of(&blocks, 1);
    assert_eq!(spans_text(spans), "second paragraph");
    assert_eq!(
        indent, 1,
        "loose item continuations indent under the item's text"
    );

    let (marker, text, ..) = item_of(&blocks, 2);
    assert_eq!(marker, ListMarker::Bullet);
    assert_eq!(text, "next");
}

#[test]
fn tight_item_content_after_a_nested_block_stays_in_the_item() {
    let blocks = parse_body(
        "- doc
  ```rust
  fn x() {}
  ```
  after
",
    );
    assert_eq!(
        blocks.len(),
        3,
        "marker row, code, and one continuation row"
    );

    let (marker, text, indent, _) = item_of(&blocks, 0);
    assert_eq!(marker, ListMarker::Bullet);
    assert_eq!(text, "doc");
    assert_eq!(indent, 0);
    assert!(matches!(
        &blocks[1],
        MarkdownBlock::Code {
            indent: 1,
            quote: false,
            ..
        }
    ));

    let (spans, indent, _) = paragraph_of(&blocks, 2);
    assert_eq!(spans_text(spans), "after");
    assert_eq!(indent, 1, "the continuation stays under the item's text");
}

#[test]
fn task_markers_do_not_leak_into_following_items() {
    let blocks = parse_body("- [ ] todo\n- plain\n1. [x] done\n2. next\n");
    assert_eq!(item_of(&blocks, 0).0, ListMarker::Task(false));
    assert_eq!(item_of(&blocks, 1).0, ListMarker::Bullet);
    assert_eq!(item_of(&blocks, 2).0, ListMarker::Task(true));
    assert_eq!(item_of(&blocks, 3).0, ListMarker::Ordered(2));
}

#[test]
fn quoted_text_after_an_item_flushes_the_item_first() {
    let blocks = parse_body("- text\n  > quoted\n");
    assert_eq!(blocks.len(), 2);
    assert_eq!(item_of(&blocks, 0).1, "text");
    let (_, indent, quote) = paragraph_of(&blocks, 1);
    assert!(quote, "the quoted paragraph carries the quote flag");
    assert_eq!(indent, 1, "quote content stays under the item's text");
}

#[test]
fn a_rule_after_item_text_keeps_its_order() {
    let blocks = parse_body("- text\n  ***\n");
    assert_eq!(blocks.len(), 2);
    assert_eq!(item_of(&blocks, 0).1, "text");
    assert!(matches!(
        &blocks[1],
        MarkdownBlock::ThematicBreak {
            indent: 1,
            quote: false
        }
    ));
}

#[test]
fn nested_code_and_tables_carry_indent_and_quote() {
    let blocks =
        parse_body("- fenced\n\n  ```rust\n  fn x() {}\n  ```\n\n> | a |\n> |---|\n> | b |\n");
    assert_eq!(blocks.len(), 3);

    let (marker, text, indent, _) = item_of(&blocks, 0);
    assert_eq!(marker, ListMarker::Bullet);
    assert_eq!(text, "fenced");
    assert_eq!(indent, 0);

    assert!(matches!(
        &blocks[1],
        MarkdownBlock::Code {
            indent: 1,
            quote: false,
            ..
        }
    ));
    assert!(matches!(
        &blocks[2],
        MarkdownBlock::Table {
            indent: 0,
            quote: true,
            ..
        }
    ));
}

#[test]
fn task_markers_carry_their_checked_state() {
    let blocks = parse_body("- [ ] todo\n- [x] done\n");
    assert_eq!(item_of(&blocks, 0).0, ListMarker::Task(false));
    assert_eq!(item_of(&blocks, 1).0, ListMarker::Task(true));
}

#[test]
fn quotes_mark_their_paragraphs_and_lists() {
    let blocks = parse_body("> quoted\n>\n> - listed\n\nplain");
    let (_, _, quote) = paragraph_of(&blocks, 0);
    assert!(quote, "quoted paragraphs carry the quote flag");
    assert!(item_of(&blocks, 1).3, "quoted list items carry it too");
    assert!(!paragraph_of(&blocks, 2).2);
}

#[test]
fn fenced_code_highlights_known_languages_and_keeps_the_info_string() {
    let blocks = parse_body("```rust\nfn main() {}\n```\n\n```text\nplain\n```");
    assert_eq!(blocks.len(), 2);

    let MarkdownBlock::Code {
        language, lines, ..
    } = &blocks[0]
    else {
        panic!("the first block is code");
    };
    assert_eq!(language.as_deref(), Some("rust"));
    assert!(
        lines
            .lines
            .iter()
            .flat_map(|line| &line.spans)
            .any(|span| span.role == Role::Keyword),
        "rust fences highlight through the grammar"
    );

    let MarkdownBlock::Code {
        language, lines, ..
    } = &blocks[1]
    else {
        panic!("the second block is code");
    };
    assert_eq!(language.as_deref(), Some("text"));
    assert!(
        lines
            .lines
            .iter()
            .flat_map(|line| &line.spans)
            .all(|span| span.role == Role::Text),
        "unknown languages render plain"
    );
}

#[test]
fn tables_parse_header_first_with_column_positions() {
    let blocks = parse_body("| a | b |\n|---|---|\n| 1 | 2 |\n| 3 | 4 |\n");
    let MarkdownBlock::Table { table, .. } = &blocks[0] else {
        panic!("the block is a table");
    };

    assert_eq!(table.rows.len(), 3);
    assert!(table.rows[0].header);
    assert!(!table.rows[1].header);

    let header: Vec<String> = table.rows[0]
        .cells
        .iter()
        .map(|cell| spans_text(&cell.spans))
        .collect();
    assert_eq!(header, vec!["a", "b"]);
    assert_eq!(
        table.rows[0]
            .cells
            .iter()
            .map(|cell| cell.column)
            .collect::<Vec<_>>(),
        vec![1, 2]
    );
    assert_eq!(spans_text(&table.rows[2].cells[1].spans), "4");
}

#[test]
fn images_render_their_alt_text_and_html_renders_nothing() {
    let blocks = parse_body("see ![the logo](logo.png) now\n\n<div>hidden</div>\n");
    assert_eq!(blocks.len(), 1, "the html block renders no block at all");
    let (spans, ..) = paragraph_of(&blocks, 0);
    assert_eq!(spans_text(spans), "see the logo now");
}

#[test]
fn set_source_reparses_and_blocks_reset() {
    let mut cx = TestAppContext::single();
    cx.update(gpui_native_theme::Theme::init);
    let state = cx.new(|_| MarkdownViewState::new("test-md", "# old\n"));

    cx.update(|cx| {
        state.update(cx, |state, cx| state.set_source("- a\n- b\n", cx));
    });

    let (source, count) = cx.update(|cx| {
        let state = state.read(cx);
        (state.source().to_string(), state.blocks().len())
    });
    assert_eq!(source, "- a\n- b\n");
    assert_eq!(count, 2, "the block list reflects the new source");
}

struct Host {
    view: Entity<MarkdownViewState>,
}

impl Render for Host {
    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
        div().size_full().child(self.view.clone())
    }
}

fn view_window(source: &str) -> (TestAppContext, VisualTestContext, Entity<MarkdownViewState>) {
    let mut cx = TestAppContext::single();
    cx.update(gpui_native_theme::Theme::init);
    let state = MarkdownViewState::new("test-md", source);
    let state_cell: Rc<RefCell<Option<Entity<MarkdownViewState>>>> = Rc::new(RefCell::new(None));
    let cell = state_cell.clone();
    let window = cx.add_window(move |_, cx| {
        let view = cx.new(|_| state);
        cell.borrow_mut().replace(view.clone());
        Host { view }
    });
    let state = state_cell.borrow().clone().expect("state captured");
    let mut visual = VisualTestContext::from_window(window.into(), &cx);
    visual.update(|window, cx| {
        window.draw(cx).clear(cx);
    });
    (cx, visual, state)
}

#[test]
fn blocks_render_virtualized_and_scroll_to_a_block() {
    let mut source = String::new();
    for paragraph in 0..200 {
        source.push_str(&format!("paragraph {paragraph} with some body text\n\n"));
    }
    let (_cx, mut visual, state) = view_window(&source);

    assert!(
        visual.debug_bounds("test-md-block-0").is_some(),
        "the first block renders"
    );
    assert!(
        visual.debug_bounds("test-md-block-150").is_none(),
        "blocks past the viewport never render"
    );

    state.update_in(&mut visual, |state, _window, _cx| {
        state.scroll_to_block(150)
    });
    visual.update(|window, cx| {
        window.draw(cx).clear(cx);
    });

    assert!(
        visual.debug_bounds("test-md-block-150").is_some(),
        "scrolling brings the target block in"
    );
    assert!(
        visual.debug_bounds("test-md-block-0").is_none(),
        "the first block scrolled out"
    );
    assert!(
        visual.debug_bounds("test-md-block-199").is_none(),
        "blocks past the target stay unrendered"
    );
}

#[test]
fn clicking_a_link_opens_its_destination() {
    let (_cx, mut visual, _state) = view_window("[click me](https://example.com/welcome)");

    let block = visual
        .debug_bounds("test-md-block-0")
        .expect("the paragraph renders");

    visual.simulate_event(MouseDownEvent {
        position: point(block.left() + px(4.), block.center().y),
        button: MouseButton::Left,
        ..Default::default()
    });
    visual.simulate_event(MouseUpEvent {
        position: point(block.left() + px(4.), block.center().y),
        button: MouseButton::Left,
        ..Default::default()
    });

    assert_eq!(
        visual.opened_url().as_deref(),
        Some("https://example.com/welcome"),
        "the link's destination opens through the platform"
    );
}

/// Parses without an app context; the view reuses this path.
fn parse_body(source: &str) -> Vec<MarkdownBlock> {
    let state = MarkdownViewState::new("parse-md", source);
    state.blocks().to_vec()
}