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

use gpui::{
    AppContext as _, Context, Entity, IntoElement, ParentElement as _, Render, Styled as _,
    TestAppContext, VisualTestContext, Window, div,
};
use gpui_native_editor::code_view::CodeViewState;
use gpui_native_editor::highlight::{HighlightedCode, Language, Role, highlight};

fn spans_with_role(code: &HighlightedCode, role: Role) -> Vec<&str> {
    code.lines
        .iter()
        .flat_map(|line| line.spans.iter())
        .filter(|span| span.role == role)
        .map(|span| span.text.as_ref())
        .collect()
}

#[test]
fn a_rust_snippet_gets_its_roles_from_the_grammar() {
    let source = "// a comment\nfn main() {\n    let greeting = \"hello\";\n}\n";
    let code = highlight(source, Language::Rust);

    assert_eq!(code.lines.len(), 5, "a trailing newline ends an empty line");
    assert!(spans_with_role(&code, Role::Comment).contains(&"// a comment"));
    assert!(
        spans_with_role(&code, Role::Keyword)
            .iter()
            .any(|text| text.contains("fn"))
    );
    assert!(
        spans_with_role(&code, Role::Keyword)
            .iter()
            .any(|text| text.contains("let"))
    );
    assert!(spans_with_role(&code, Role::Function).contains(&"main"));
    assert!(
        spans_with_role(&code, Role::String)
            .iter()
            .any(|text| text.contains("hello"))
    );
}

#[test]
fn a_capture_spanning_newlines_styles_both_lines() {
    let source = "let text = \"a\nb\";\n";
    let code = highlight(source, Language::Rust);

    assert!(
        code.lines[0]
            .spans
            .iter()
            .any(|span| span.role == Role::String && span.text.contains("\"a")),
        "the string opens on the first line"
    );
    assert!(
        code.lines[1]
            .spans
            .iter()
            .any(|span| span.role == Role::String && span.text.contains("b\"")),
        "and continues on the second"
    );
}

#[test]
fn set_source_rehighlights_with_the_new_language() {
    let mut cx = TestAppContext::single();
    let state = cx.new(|_| CodeViewState::new("test-code", "fn main() {}\n", Language::Rust));

    cx.update(|cx| {
        state.update(cx, |state, cx| {
            state.set_source("def main():\n    pass\n", Language::Python, cx);
        });
    });

    let code = cx.update(|cx| state.read(cx).code().clone());
    assert!(
        spans_with_role(&code, Role::Keyword)
            .iter()
            .any(|text| text.contains("def")),
        "python's def highlights as a keyword"
    );
    assert!(spans_with_role(&code, Role::Function).contains(&"main"));
}

struct Host {
    code: Entity<CodeViewState>,
}

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

fn code_view_window(
    line_count: usize,
) -> (TestAppContext, VisualTestContext, Entity<CodeViewState>) {
    let mut cx = TestAppContext::single();
    cx.update(gpui_native_theme::Theme::init);
    let source: String = (0..line_count)
        .map(|line| format!("fn line_{line}() {{}}\n"))
        .collect();
    let state = CodeViewState::new("test-code", source, Language::Rust);
    let state_cell: Rc<RefCell<Option<Entity<CodeViewState>>>> = Rc::new(RefCell::new(None));
    let cell = state_cell.clone();
    let window = cx.add_window(move |_, cx| {
        let code = cx.new(|_| state);
        cell.borrow_mut().replace(code.clone());
        Host { code }
    });
    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 rows_render_virtualized_and_scroll() {
    let (_cx, mut visual, state) = code_view_window(80);

    assert!(
        visual.debug_bounds("test-code-row-0").is_some(),
        "the first row renders"
    );
    assert!(
        visual.debug_bounds("test-code-row-79").is_none(),
        "rows past the viewport never render"
    );

    state.update_in(&mut visual, |state, _window, _cx| state.scroll_to_line(79));
    visual.update(|window, cx| {
        window.draw(cx).clear(cx);
    });

    assert!(
        visual.debug_bounds("test-code-row-79").is_some(),
        "scrolling brings the last row in"
    );
    assert!(
        visual.debug_bounds("test-code-row-0").is_none(),
        "the first row scrolled out"
    );
}