use axum::extract::{Query, State};
use axum::response::IntoResponse;
use axum::routing::get;
use axum::Router;
use futures_util::{stream, StreamExt};
use hemplate::Hemplate;
use hemx::{Html, IntoEffect};
use hemx_axum::{
    interactions, runtime_js, runtime_js_path, sse, EffectResponse, Form, HandlerErrorContext,
    HandlerFailure, InteractionHandlers, InteractionRequest, IntoHandlerFailure, PageRequest,
};
use hemx_v0_examples::ui;
use hemx_v0_examples::ui::{auth, counter, notifications, page_swap, todo_row, todos, wizard};
use std::collections::BTreeMap;
use std::convert::Infallible;
use std::net::SocketAddr;
use std::sync::{Arc, Mutex};
use std::time::Duration;

#[derive(Default)]
struct ExampleState {
    counter: Mutex<u64>,
    todos: Mutex<Vec<TodoRecord>>,
    wizard_step: Mutex<u8>,
}

#[derive(Clone)]
struct TodoRecord {
    // Domain/SQL-shaped rows stay as boring Rust data; hemplate view structs are derived at render/update boundaries.
    // req: examples/001 req: view/001
    id: u64,
    title: String,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
struct TodoId(u64);

impl std::fmt::Display for TodoId {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl std::str::FromStr for TodoId {
    type Err = std::num::ParseIntError;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        value.parse().map(Self)
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
struct TodoTitle(String);

impl TodoTitle {
    fn as_str(&self) -> &str {
        &self.0
    }

    fn into_string(self) -> String {
        self.0
    }
}

impl std::fmt::Display for TodoTitle {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

impl std::str::FromStr for TodoTitle {
    type Err = Infallible;

    fn from_str(value: &str) -> Result<Self, Self::Err> {
        Ok(Self(value.trim().to_owned()))
    }
}

#[hemx::form("new_todo")]
struct NewTodo {
    title: TodoTitle,
}

#[hemx::form("rename_todo")]
struct RenameTodo {
    id: TodoId,
    title: TodoTitle,
}

#[hemx::form("delete_todo")]
struct DeleteTodo {
    id: TodoId,
}

#[hemx::form("wizard_input")]
struct WizardInput {
    step: String,
}

#[hemx::form("credentials")]
struct Credentials {
    email: String,
    password: String,
}

#[derive(Debug)]
struct AppError(String);

impl std::fmt::Display for AppError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

impl std::error::Error for AppError {}

impl IntoHandlerFailure for AppError {
    fn into_handler_failure(self, context: HandlerErrorContext) -> HandlerFailure {
        HandlerFailure::effects(
            notifications::notifications.set(format!("Could not save todo: {}", self.0)),
            context,
        )
    }
}

#[derive(Hemplate)]
struct Todos {
    summary: String,
    notice: String,
    rows: Vec<TodoRow>,
}

#[derive(Hemplate)]
#[hemplate = "partials"]
struct TodoRow {
    id: TodoId,
    title: String,
}

impl hemx::KeyedPartial for TodoRow {
    fn hemx_key(&self) -> String {
        self.id.to_string()
    }
}

#[derive(Hemplate)]
struct Counter;

#[derive(Hemplate)]
struct Wizard;

#[derive(Hemplate)]
struct Auth;

#[derive(Hemplate)]
struct Notifications;

#[derive(Hemplate)]
struct PageSwap {
    content: Html,
    title: &'static str,
}

#[derive(Hemplate)]
struct AppShell {
    runtime_src: &'static str,
    body: Html,
}

#[derive(Hemplate)]
#[hemplate = "partials"]
struct DocsContent {
    message: &'static str,
}

#[tokio::main]
async fn main() {
    let state = Arc::new(ExampleState::default());
    let app = Router::new()
        .route("/", get(home).post(interact))
        .route("/docs", get(docs).post(interact))
        .route("/events", get(events))
        .route(runtime_js_path(), get(runtime))
        .with_state(state);

    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
    println!("hemx v0 examples: http://{addr}");
    axum::serve(listener, app).await.unwrap();
}

// req: examples/001
async fn home(request: PageRequest) -> impl IntoResponse {
    request
        .page_html(all_examples(), shell)
        .title("hemx v0 examples")
        .fingerprint(ui::BUILD_FINGERPRINT)
}

// req: page_swap/002, req: examples/001
async fn docs(request: PageRequest) -> impl IntoResponse {
    let partial = render_page_swap("Docs", "This page was swapped without a full reload.");
    request
        .page_html(partial, shell)
        .title("Docs")
        .fingerprint(ui::BUILD_FINGERPRINT)
}

async fn interact(
    State(state): State<Arc<ExampleState>>,
    request: InteractionRequest,
) -> Result<EffectResponse, impl IntoResponse> {
    request.dispatch_async(handlers(state)).await
}

async fn runtime() -> impl IntoResponse {
    runtime_js()
}

// req: push/001, req: push/003, req: examples/001
async fn events(Query(params): Query<BTreeMap<String, String>>) -> impl IntoResponse {
    if params.contains_key("once") {
        let effect = notifications::notifications.set("Server event #1");
        return sse(stream::iter([Ok::<_, Infallible>(
            effect.into_batch(ui::BUILD_FINGERPRINT),
        )])
        .boxed());
    }

    let batches = stream::unfold(1_u64, |count| async move {
        tokio::time::sleep(Duration::from_secs(3)).await;
        let effect = notifications::notifications.set(format!("Server event #{count}"));
        Some((
            Ok::<_, Infallible>(effect.into_batch(ui::BUILD_FINGERPRINT)),
            count + 1,
        ))
    })
    .boxed();
    sse(batches)
}

#[hemx::app(
    counter_handlers,
    todo_handlers,
    todo_row_handlers,
    wizard_handlers,
    auth_handlers
)]
fn handlers(state: Arc<ExampleState>) -> InteractionHandlers {
    interactions(ui::BUILD_FINGERPRINT)
}

fn all_examples() -> Html {
    // req: html_safety/001 req: html_safety/002 req: component/003
    Html::join([
        counter::page(&Counter),
        ui::page(&todos_view(&[])),
        wizard::page(&Wizard),
        auth::page(&Auth),
        render_page_swap("Welcome", "Welcome"),
        notifications::page(&Notifications),
    ])
}

fn shell(body: Html) -> Html {
    // req: html_safety/001 req: html_safety/002 req: axum_integration/001 req: component/003
    ui::page(&AppShell {
        runtime_src: runtime_js_path(),
        body,
    })
}

#[hemx::component("counter")]
mod counter_handlers {
    use super::*;

    #[hemx::handler]
    async fn increment(State(state): State<Arc<ExampleState>>) -> impl IntoEffect {
        // req: examples/001
        let mut counter = state.counter.lock().unwrap();
        *counter += 1;
        counter::counter_value.set(*counter)
    }
}

#[hemx::component("todos")]
mod todo_handlers {
    use super::*;

    #[hemx::handler]
    async fn add_todo(
        State(state): State<Arc<ExampleState>>,
        Form(form): Form<NewTodo>,
    ) -> Result<impl IntoEffect, AppError> {
        // req: examples/001 req: canonical_authoring/003
        if form.title.as_str().is_empty() {
            return Ok((
                todos::new_todo.error("title", "Title required"),
                todos::new_todo.focus("title"),
                todos::summary.set(todo_summary(&state.todos.lock().unwrap())),
                todos::notice.set("Add a title to create a todo"),
            ));
        }
        if form.title.as_str() == "fail-db" {
            return Err(AppError("todo store unavailable".to_owned()));
        }

        let mut todos = state.todos.lock().unwrap();
        let id = todos.last().map_or(1, |todo| todo.id + 1);
        let title = form.title.into_string();
        todos.push(TodoRecord {
            id,
            title: title.clone(),
        });
        let summary = todo_summary(&todos);
        Ok((
            todos::todo_row.append(TodoRow {
                id: TodoId(id),
                title: title.clone(),
            }),
            todos::summary.set(summary),
            todos::notice.set(format!("Added {title}")),
            todos::new_todo.clear(),
        ))
    }
}

#[hemx::component("todo_row")]
mod todo_row_handlers {
    use super::*;

    #[hemx::handler]
    async fn rename_todo(
        State(state): State<Arc<ExampleState>>,
        Form(form): Form<RenameTodo>,
    ) -> impl IntoEffect {
        rename_todo_effect(state, form)
    }

    #[hemx::handler]
    async fn delete_todo(
        State(state): State<Arc<ExampleState>>,
        Form(form): Form<DeleteTodo>,
    ) -> impl IntoEffect {
        delete_todo_effect(state, form)
    }
}

#[hemx::component("wizard")]
mod wizard_handlers {
    use super::*;

    #[hemx::handler]
    async fn next_step(
        State(state): State<Arc<ExampleState>>,
        Form(form): Form<WizardInput>,
    ) -> impl IntoEffect {
        // req: examples/001
        let _submitted_step = form.step;
        let mut step = state.wizard_step.lock().unwrap();
        *step += 1;
        wizard::wizard_step.set(format!("Step {}", *step + 1))
    }
}

#[hemx::component("auth")]
mod auth_handlers {
    use super::*;

    #[hemx::handler]
    async fn login(
        State(_state): State<Arc<ExampleState>>,
        Form(credentials): Form<Credentials>,
    ) -> impl IntoEffect {
        // req: examples/001
        let ok = credentials.email == "demo@example.com" && !credentials.password.is_empty();
        auth::login_status.set(if ok {
            "Signed in as demo@example.com"
        } else {
            "Try demo@example.com with any password"
        })
    }
}

fn rename_todo_effect(state: Arc<ExampleState>, form: RenameTodo) -> impl IntoEffect {
    // req: examples/001 req: canonical_authoring/003
    if form.title.as_str().is_empty() {
        return Some((
            todo_row::rename_todo_form.focus("title"),
            todos::notice.set("Add a title before renaming"),
        ));
    }

    let mut todos = state.todos.lock().unwrap();
    todos
        .iter_mut()
        .find(|todo| todo.id == form.id.0)
        .map(|todo| {
            todo.title = form.title.into_string();
            (
                todos::todo_row.replace(TodoRow {
                    id: form.id,
                    title: todo.title.clone(),
                }),
                todos::notice.set("Todo renamed"),
            )
        })
}

fn delete_todo_effect(state: Arc<ExampleState>, form: DeleteTodo) -> impl IntoEffect {
    // req: examples/001 req: canonical_authoring/003
    let mut todos = state.todos.lock().unwrap();
    let before = todos.len();
    todos.retain(|todo| todo.id != form.id.0);
    let deleted = todos.len() != before;
    let summary = todo_summary(&todos);
    (
        deleted.then(|| todos::todo_row.remove(form.id)),
        deleted.then(|| todos::summary.set(summary)),
        deleted.then(|| todos::notice.set("Todo deleted")),
    )
}

fn todos_view(todos: &[TodoRecord]) -> Todos {
    // req: html_safety/002 req: view/001 req: canonical_authoring/003
    Todos {
        summary: todo_summary(todos),
        notice: String::new(),
        rows: todo_rows(todos),
    }
}

#[cfg(test)]
fn refresh_todo_rows_effect(todos: &[TodoRecord]) -> impl IntoEffect {
    // req: canonical_authoring/003
    let row_updates = todo_rows(todos)
        .into_iter()
        .map(|row| todos::todo_row.replace(row))
        .collect::<Vec<_>>();
    (
        row_updates,
        todos::summary.set(todo_summary(todos)),
        todos::notice.set("Todos refreshed"),
    )
}

fn todo_rows(todos: &[TodoRecord]) -> Vec<TodoRow> {
    todos
        .iter()
        .map(|todo| TodoRow {
            id: TodoId(todo.id),
            title: todo.title.clone(),
        })
        .collect()
}

fn todo_summary(todos: &[TodoRecord]) -> String {
    match todos.len() {
        0 => "No todos".to_owned(),
        1 => "1 todo".to_owned(),
        count => format!("{count} todos"),
    }
}

fn render_page_swap(title: &'static str, message: &'static str) -> Html {
    // req: html_safety/002 req: view/001 req: component/003
    page_swap::page(&PageSwap {
        content: render_docs_content(message),
        title,
    })
}

fn render_docs_content(message: &'static str) -> Html {
    // req: html_safety/002 req: view/001 req: component/003
    ui::page(&DocsContent { message })
}

#[cfg(test)]
mod tests {
    use super::*;
    use hemx_test::{
        article_selector, document_title_selector, escaped_markup_selector, heading_selector,
        inspect_batch, keyed_items_selector, keyed_selector, list_item_selector,
        page_nav_link_selector, prose_selector, root_element_selector, runtime_script_selector,
    };
    use scraper::{Html, Selector};

    fn selector(value: &str) -> Selector {
        Selector::parse(value).expect("test selector parses")
    }

    fn form<I>(handle: hemx::Handle<I>, fields: &[(&str, &str)]) -> hemx_axum::InteractionForm {
        hemx_axum::InteractionForm::for_handle(
            handle,
            fields
                .iter()
                .map(|(name, value)| ((*name).to_owned(), (*value).to_owned())),
        )
    }

    // req: html_safety/002 req: view/001 req: test/005
    #[test]
    fn shell_is_rendered_by_a_hemplate_view() {
        let html = shell(render_page_swap("Welcome", "Welcome"));
        let document = Html::parse_document(html.as_str());
        assert_eq!(
            document
                .select(&selector(document_title_selector()))
                .next()
                .map(|title| title.text().collect::<String>()),
            Some("hemx v0 examples".to_owned())
        );
        assert_eq!(
            document
                .select(&selector(runtime_script_selector()))
                .count(),
            1
        );
        assert_eq!(
            document
                .select(&selector(&root_element_selector("main", "docs")))
                .count(),
            1
        );
        assert!(
            document
                .root_element()
                .text()
                .all(|text| !text.contains("{+=")),
            "hemplate insertion markers must not leak into rendered text"
        );
    }

    // req: html_safety/002 req: view/001 req: test/005
    #[test]
    fn docs_content_payload_is_rendered_by_a_hemplate_view() {
        let html = render_docs_content("This content came from a generated update response.");
        let document = Html::parse_fragment(html.as_str());
        assert_eq!(
            document
                .select(&selector(&heading_selector("", 1)))
                .next()
                .map(|heading| heading.text().collect::<String>()),
            Some("Docs".to_owned())
        );
        assert_eq!(
            document
                .select(&selector(&prose_selector("")))
                .next()
                .map(|paragraph| paragraph.text().collect::<String>()),
            Some("This content came from a generated update response.".to_owned())
        );
    }

    // req: html_safety/002 req: view/001 req: test/005
    #[test]
    fn docs_page_partial_is_rendered_by_a_hemplate_view() {
        let html = render_page_swap("Docs", "This page was swapped without a full reload.");
        let document = Html::parse_fragment(html.as_str());
        assert_eq!(
            document
                .select(&selector(&root_element_selector("main", "docs")))
                .count(),
            1
        );
        assert_eq!(document.select(&selector(article_selector())).count(), 1);
        assert_eq!(
            document
                .select(&selector(&page_nav_link_selector("/docs")))
                .count(),
            1
        );
        assert_eq!(
            document
                .select(&selector(&heading_selector("article", 1)))
                .next()
                .map(|heading| heading.text().collect::<String>()),
            Some("Docs".to_owned())
        );
    }

    // req: html_safety/002 req: view/001 req: test/005
    #[test]
    fn todos_payload_is_rendered_by_a_hemplate_view() {
        let todos = vec![TodoRecord {
            id: 7,
            title: "<b>Ship v0</b>".to_owned(),
        }];

        let html = ui::page(&todos_view(&todos));
        let document = Html::parse_fragment(html.as_str());
        let rows = document
            .select(&selector(&keyed_items_selector("li")))
            .collect::<Vec<_>>();
        assert_eq!(rows.len(), 1);
        let row = document
            .select(&selector(&keyed_selector("li", 7)))
            .next()
            .expect("generated keyed row");
        assert!(row.text().collect::<String>().contains("<b>Ship v0</b>"));
        assert!(document
            .select(&selector(&escaped_markup_selector("b")))
            .next()
            .is_none());
        assert_eq!(
            document
                .select(&selector("[data-hemx-error-for='title']"))
                .count(),
            2,
            "add and rename forms expose generated field-error targets"
        );
        assert_eq!(
            document.select(&selector("[data-hemx-error]")).count(),
            1,
            "the app exposes one root-scoped transport error outlet"
        );
    }

    // req: canonical_authoring/003 req: test/005
    #[test]
    fn reusable_todo_partial_supports_dynamic_replace_batches() {
        let todos = vec![
            TodoRecord {
                id: 7,
                title: "Ship v0".to_owned(),
            },
            TodoRecord {
                id: 8,
                title: "Write docs".to_owned(),
            },
        ];

        let initial = ui::page(&todos_view(&todos));
        let document = Html::parse_fragment(initial.as_str());
        assert_eq!(
            document
                .select(&selector(&keyed_items_selector("li")))
                .count(),
            2
        );

        let refresh =
            inspect_batch(refresh_todo_rows_effect(&todos).into_batch(ui::BUILD_FINGERPRINT));
        assert_eq!(refresh.op_count(), 4);
        assert!(refresh.replaces_keyed_html_containing(todos::todo_row, "7", "Ship v0"));
        assert!(refresh.replaces_keyed_html_containing(todos::todo_row, "8", "Write docs"));
        assert!(refresh.updates_text(todos::summary));
        assert!(refresh.updates_text(todos::notice));
    }

    // req: html_safety/002 req: view/001 req: test/005
    #[test]
    fn empty_todos_payload_is_rendered_by_a_hemplate_view() {
        let html = ui::page(&todos_view(&[]));
        let document = Html::parse_fragment(html.as_str());
        let rows = document
            .select(&selector(&list_item_selector("")))
            .collect::<Vec<_>>();
        assert_eq!(rows.len(), 0);
    }

    // req: examples/001 req: page_swap/002 req: page_swap/003 req: component/005 req: public_api/003 req: test/005
    #[tokio::test]
    async fn registry_dispatches_generated_keyed_crud_effects() {
        let state = Arc::new(ExampleState::default());

        let counter = inspect_batch(
            InteractionRequest::from(form(counter::increment, &[]))
                .dispatch_async(handlers(state.clone()))
                .await
                .unwrap()
                .batch,
        );
        assert_eq!(*state.counter.lock().unwrap(), 1);
        assert!(counter.updates_text(counter::counter_value));
        assert!(counter.payload_contains("1"));

        let validation = inspect_batch(
            InteractionRequest::from(form(todos::add_todo, &[("title", "   ")]))
                .dispatch_async(handlers(state.clone()))
                .await
                .unwrap()
                .batch,
        );
        assert!(state.todos.lock().unwrap().is_empty());
        assert!(validation.payload_contains("Title required"));

        let store_failure = inspect_batch(
            InteractionRequest::from(form(todos::add_todo, &[("title", "fail-db")]))
                .dispatch_async(handlers(state.clone()))
                .await
                .unwrap()
                .batch,
        );
        assert!(state.todos.lock().unwrap().is_empty());
        assert!(store_failure.updates_text(notifications::notifications));
        assert!(store_failure.payload_contains("todo store unavailable"));

        let add = inspect_batch(
            InteractionRequest::from(form(todos::add_todo, &[("title", "Ship v0")]))
                .dispatch_async(handlers(state.clone()))
                .await
                .unwrap()
                .batch,
        );
        assert_eq!(state.todos.lock().unwrap()[0].title, "Ship v0");
        assert_eq!(add.op_count(), 4);
        assert!(add.inserts_html_containing(todos::todo_row, "1", "Ship v0"));
        assert!(add.updates_text(todos::summary));
        assert!(add.updates_text(todos::notice));
        assert!(add.payload_contains("Added Ship v0"));
        assert!(add.resets_form(todos::new_todo));

        let rename_validation = inspect_batch(
            InteractionRequest::from(form(
                todo_row::rename_todo,
                &[("id", "1"), ("title", "   ")],
            ))
            .dispatch_async(handlers(state.clone()))
            .await
            .unwrap()
            .batch,
        );
        assert_eq!(state.todos.lock().unwrap()[0].title, "Ship v0");
        assert!(rename_validation.payload_contains("Add a title before renaming"));
        assert!(rename_validation.updates_text(todos::notice));

        let rename = inspect_batch(
            InteractionRequest::from(form(
                todo_row::rename_todo,
                &[("id", "1"), ("title", "Ship 1.0")],
            ))
            .dispatch_async(handlers(state.clone()))
            .await
            .unwrap()
            .batch,
        );
        assert_eq!(state.todos.lock().unwrap()[0].title, "Ship 1.0");
        assert_eq!(rename.op_count(), 2);
        assert!(rename.replaces_keyed_html_containing(todos::todo_row, "1", "Ship 1.0"));
        assert!(rename.updates_text(todos::notice));

        let delete = inspect_batch(
            InteractionRequest::from(form(todo_row::delete_todo, &[("id", "1")]))
                .dispatch_async(handlers(state.clone()))
                .await
                .unwrap()
                .batch,
        );
        assert!(state.todos.lock().unwrap().is_empty());
        assert_eq!(delete.op_count(), 3);
        assert!(delete.removes_key(todos::todo_row, "1"));
        assert!(delete.updates_text(todos::summary));
        assert!(delete.updates_text(todos::notice));

        let missing_delete = inspect_batch(
            InteractionRequest::from(form(todo_row::delete_todo, &[("id", "99")]))
                .dispatch_async(handlers(state.clone()))
                .await
                .unwrap()
                .batch,
        );
        assert!(missing_delete.is_empty());

        let wizard = inspect_batch(
            InteractionRequest::from(form(wizard::next_step, &[("step", "1")]))
                .dispatch_async(handlers(state.clone()))
                .await
                .unwrap()
                .batch,
        );
        assert!(wizard.updates_text(wizard::wizard_step));
        assert!(wizard.payload_contains("Step 2"));

        let auth = inspect_batch(
            InteractionRequest::from(form(
                auth::login,
                &[("email", "demo@example.com"), ("password", "secret")],
            ))
            .dispatch_async(handlers(state))
            .await
            .unwrap()
            .batch,
        );
        assert!(auth.updates_text(auth::login_status));
        assert!(auth.payload_contains("Signed in as demo@example.com"));
    }
}