use crate::queries::{ListTodos, Todo};
use livevue_rs::{RenderContext, global, mangle};
use maud::{html, Markup};

/// Root page component: renders the full todo list with add form.
///
/// Reads signals:
/// - `newTodo` (global, server-relevant): the text input value
///
/// Exercises:
/// - `cx.run()` for data fetching
/// - `cx.signal()` with `global()` scoping + `Signal::val` in expressions
/// - `cx.signal()` with `mangle().client_only()` scoping (in todo_item)
/// - DataStar `data-bind`, `data-on-click`, `data-attr` attributes
/// - `@post()` actions for mutations
pub async fn todo_list(cx: &mut RenderContext) -> anyhow::Result<Markup> {
    // Fetch all todos
    let todos = cx.run(ListTodos).await?;

    // Global signal for the "new todo" input. This call does two things:
    // 1. Records "newTodo" as a touched signal (for demangling tracking)
    // 2. Returns a Signal struct whose .val is "$newTodo" for expressions
    let new_todo = cx.signal("newTodo", global());

    let todo_count = todos.len();
    let done_count = todos.iter().filter(|t| t.completed).count();

    Ok(html! {
        div.todo-app {
            h1 { "LiveVue.rs — Todo List" }

            // Navigation link to About page (exercises tree signal + page routing)
            nav {
                span.nav-current { "Todos" }
                " | "
                button.nav-link
                    data-on-click="$tree = {page: 'About'}; @post('/render')" {
                    "About"
                }
            }

            // Add todo form.
            // data-bind-newTodo binds the input to the $newTodo signal.
            // The button uses new_todo.val ("$newTodo") in a DataStar expression.
            div.add-form {
                input
                    type="text"
                    placeholder="What needs to be done?"
                    data-bind-newTodo=""
                    ;
                button
                    data-on-click="@post('/action/add_todo')"
                    data-attr=(format!("{{disabled: {}.trim() === ''}}", new_todo.val)) {
                    "Add"
                }
            }

            // Stats
            p.stats {
                (format!("{} items, {} completed", todo_count, done_count))
            }

            // Todo items
            ul.todo-list {
                @for todo in &todos {
                    (todo_item(cx, todo))
                }
            }

            @if todos.is_empty() {
                p.empty { "No todos yet. Add one above!" }
            }
        }
    })
}

/// Renders a single todo item.
///
/// This is a static child component — called directly from `todo_list`,
/// not resolved through the component registry.
///
/// Demonstrates per-instance, client-only signal via `mangle().client_only()`.
fn todo_item(cx: &mut RenderContext, todo: &Todo) -> Markup {
    // Per-instance, client-only signal for edit mode.
    // Not used in v0 rendering, but demonstrates the mangled signal API
    // and ensures it's tracked as touched. Produces: "_editing__<id>"
    let _editing = cx.signal("editing", mangle(todo.id).client_only());

    // Build class string server-side. Since we do a full rerender on every
    // state change, there's no need for data-class here — the server knows
    // whether the todo is completed.
    let title_class = if todo.completed {
        "todo-title completed"
    } else {
        "todo-title"
    };

    html! {
        li.todo-item id=(format!("todo-{}", todo.id)) {
            // Checkbox to toggle completion.
            // `checked[expr]` is maud's syntax for conditional boolean attributes.
            input
                type="checkbox"
                checked[todo.completed]
                data-on-click=(format!("@post('/action/toggle_todo?id={}')", todo.id))
                ;

            // Title with strikethrough when completed (class set server-side)
            span class=(title_class) {
                (todo.title)
            }

            // Delete button
            button.delete-btn
                data-on-click=(format!("@post('/action/delete_todo?id={}')", todo.id))
                {
                "×"
            }
        }
    }
}