//! The few pages people open in a browser: first-start setup, sign-in for
//! the editor (with sign-up through an invite), and the join page an invite
//! link opens.

use archify_sync_protocol::SetupRequest;
use archify_sync_store::{AccountRow, InviteOutcome};
use axum::Form;
use axum::extract::{Path, Query, State};
use axum::http::{HeaderValue, StatusCode, header};
use axum::response::{Html, IntoResponse, Redirect, Response};
use serde::{Deserialize, Serialize};

use crate::api;
use crate::auth;
use crate::error::ApiErr;
use crate::metrics::{METRICS, Metrics};
use crate::oidc::{self, Person};
use crate::state::AppState;

const CSP: &str = "default-src 'none'; style-src 'unsafe-inline'; form-action 'self' vscode: vscode-insiders: vscodium: cursor: windsurf: http://127.0.0.1:* http://localhost:*; frame-ancestors 'none'; base-uri 'none'";

fn escape(text: &str) -> String {
    text.replace('&', "&")
        .replace('<', "&lt;")
        .replace('>', "&gt;")
        .replace('"', "&quot;")
        .replace('\'', "&#39;")
}

fn page(state: &AppState, title: &str, body: &str) -> Response {
    let html = format!(
        r#"<!doctype html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1">
<title>{title} · {server}</title><style>
:root {{ color-scheme: light dark; --fg: #1f2328; --muted: #59636e; --bg: #f6f8fa; --card: #fff; --line: #d1d9e0; --accent: #0969da; --bad: #d1242f; }}
@media (prefers-color-scheme: dark) {{ :root {{ --fg: #e6edf3; --muted: #9198a1; --bg: #0d1117; --card: #151b23; --line: #3d444d; --accent: #4493f8; --bad: #f85149; }} }}
body {{ margin: 0; font: 15px/1.5 system-ui, sans-serif; color: var(--fg); background: var(--bg); }}
main {{ max-width: 420px; margin: 48px auto; padding: 0 16px; }}
.card {{ background: var(--card); border: 1px solid var(--line); border-radius: 8px; padding: 24px; margin-bottom: 16px; }}
h1 {{ font-size: 20px; margin: 0 0 4px; }} h2 {{ font-size: 16px; margin: 0 0 12px; }}
p.muted {{ color: var(--muted); margin: 0 0 16px; }}
label {{ display: block; margin: 12px 0 4px; font-weight: 600; }}
input {{ width: 100%; box-sizing: border-box; padding: 8px; border: 1px solid var(--line); border-radius: 6px; background: transparent; color: inherit; font: inherit; }}
button, a.button {{ display: inline-block; margin-top: 16px; padding: 8px 16px; border: 0; border-radius: 6px; background: var(--accent); color: #fff; font: inherit; font-weight: 600; text-decoration: none; cursor: pointer; }}
.error {{ color: var(--bad); margin: 0 0 12px; }} code {{ font-size: 14px; }}
</style></head><body><main><h1>{server}</h1><p class="muted">Archify Sync</p>{body}</main></body></html>"#,
        title = escape(title),
        server = escape(&state.config.server_name),
    );
    let mut response = Html(html).into_response();
    let headers = response.headers_mut();
    headers.insert(
        header::CONTENT_SECURITY_POLICY,
        HeaderValue::from_static(CSP),
    );
    headers.insert(
        header::X_CONTENT_TYPE_OPTIONS,
        HeaderValue::from_static("nosniff"),
    );
    headers.insert(
        header::REFERRER_POLICY,
        HeaderValue::from_static("no-referrer"),
    );
    headers.insert(header::CACHE_CONTROL, HeaderValue::from_static("no-store"));
    response
}

fn error_line(error: Option<&str>) -> String {
    error
        .map(|e| format!(r#"<p class="error">{}</p>"#, escape(e)))
        .unwrap_or_default()
}

fn hidden(name: &str, value: &str) -> String {
    format!(
        r#"<input type="hidden" name="{name}" value="{}">"#,
        escape(value)
    )
}

// ------------------------------------------------------------------- setup

pub async fn setup_page(State(state): State<AppState>) -> Response {
    setup_form(&state, None).await
}

async fn setup_form(state: &AppState, error: Option<&str>) -> Response {
    if state.first_start.lock().await.is_none() {
        return page(
            state,
            "Set up",
            r#"<div class="card"><h2>Set up</h2><p>This server is set up. Sign in from VS Code with <b>Archify: Sign in to Sync Server…</b></p></div>"#,
        );
    }
    let body = format!(
        r#"<div class="card"><h2>Set up the first admin</h2><p class="muted">The first-start code is in the server's log.</p>{}
<form method="post" action="/setup">
<label for="code">First-start code</label><input id="code" name="code" autocomplete="off" required>
<label for="organisation">Organisation</label><input id="organisation" name="organisation" required>
<label for="name">Sign-in name</label><input id="name" name="name" autocomplete="username" required>
<label for="display_name">Your name</label><input id="display_name" name="display_name">
<label for="password">Password (10 characters or more)</label><input id="password" name="password" type="password" autocomplete="new-password" required>
<button type="submit">Set up</button></form></div>"#,
        error_line(error)
    );
    page(state, "Set up", &body)
}

#[derive(Deserialize)]
pub struct SetupForm {
    code: String,
    organisation: String,
    name: String,
    display_name: Option<String>,
    password: String,
}

pub async fn setup_submit(State(state): State<AppState>, Form(form): Form<SetupForm>) -> Response {
    let req = SetupRequest {
        code: form.code,
        organisation: form.organisation,
        name: form.name,
        display_name: form.display_name,
        password: form.password,
    };
    match api::setup_admin(&state, &req).await {
        Ok(account) => page(
            &state,
            "Set up",
            &format!(
                r#"<div class="card"><h2>Done</h2><p>{} is the admin. In VS Code, run <b>Archify: Sign in to Sync Server…</b> with <code>{}</code>.</p></div>"#,
                escape(&account.display_name),
                escape(&state.config.public_url)
            ),
        ),
        Err(e) => setup_form(&state, Some(&e.message)).await,
    }
}

// --------------------------------------------------------------- sign-in

/// The editor's sign-in request, carried through the password form or the identity provider.
#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct AuthorizeQuery {
    response_type: String,
    redirect_uri: String,
    state: String,
    code_challenge: String,
    code_challenge_method: String,
    invite: Option<String>,
}

impl AuthorizeQuery {
    fn to_query_string(&self) -> String {
        let mut q = url::form_urlencoded::Serializer::new(String::new());
        q.append_pair("response_type", &self.response_type)
            .append_pair("redirect_uri", &self.redirect_uri)
            .append_pair("state", &self.state)
            .append_pair("code_challenge", &self.code_challenge)
            .append_pair("code_challenge_method", &self.code_challenge_method);
        if let Some(invite) = &self.invite {
            q.append_pair("invite", invite);
        }
        q.finish()
    }
}

#[derive(Deserialize)]
pub struct AuthorizeForm {
    #[serde(flatten)]
    query: AuthorizeQuery,
    /// `signin` or `signup`.
    action: String,
    name: String,
    password: String,
    display_name: Option<String>,
}

fn check_authorize(state: &AppState, q: &AuthorizeQuery) -> Result<(), &'static str> {
    if q.response_type != "code" || q.code_challenge_method != "S256" || q.code_challenge.len() < 43
    {
        return Err("This sign-in request is not valid. Start again from VS Code.");
    }
    if !auth::redirect_allowed(state, &q.redirect_uri) {
        return Err("This sign-in request does not come from the Archify extension.");
    }
    Ok(())
}

pub async fn authorize_page(
    State(state): State<AppState>,
    Query(q): Query<AuthorizeQuery>,
) -> Response {
    authorize_form(&state, &q, None).await
}

async fn authorize_form(state: &AppState, q: &AuthorizeQuery, error: Option<&str>) -> Response {
    if let Err(message) = check_authorize(state, q) {
        let mut response = page(
            state,
            "Sign in",
            &format!(r#"<div class="card">{}</div>"#, error_line(Some(message))),
        );
        *response.status_mut() = StatusCode::BAD_REQUEST;
        return response;
    }
    let fields = [
        hidden("response_type", &q.response_type),
        hidden("redirect_uri", &q.redirect_uri),
        hidden("state", &q.state),
        hidden("code_challenge", &q.code_challenge),
        hidden("code_challenge_method", &q.code_challenge_method),
        q.invite
            .as_deref()
            .map(|i| hidden("invite", i))
            .unwrap_or_default(),
    ]
    .concat();
    // Single sign-on first when the server has it; the password form stays for local accounts.
    let mut body = state
        .oidc
        .as_ref()
        .map(|o| {
            format!(
                r#"<div class="card"><h2>Sign in for VS Code</h2>{}<a class="button" href="/oidc/start?{}">Sign in with {}</a></div>"#,
                error_line(error),
                escape(&q.to_query_string()),
                escape(&o.config.label),
            )
        })
        .unwrap_or_default();
    let (title, error) = if body.is_empty() {
        ("Sign in for VS Code", error)
    } else {
        ("Or with a password", None)
    };
    body.push_str(&format!(
        r#"<div class="card"><h2>{title}</h2>{}
<form method="post" action="/authorize">{fields}{}
<label for="name">Sign-in name</label><input id="name" name="name" autocomplete="username" required>
<label for="password">Password</label><input id="password" name="password" type="password" autocomplete="current-password" required>
<button type="submit">Sign in</button></form></div>"#,
        error_line(error),
        hidden("action", "signin"),
    ));
    // A valid invite lets someone new make an account in the space's organisation.
    if let Some(invite) = &q.invite
        && let Ok(Some((_, space_name))) =
            state.store.invite_organisation(&auth::sha256(invite)).await
    {
        body.push_str(&format!(
                r#"<div class="card"><h2>New here?</h2><p class="muted">You were invited to <b>{}</b>. Make an account.</p>
<form method="post" action="/authorize">{fields}{}
<label for="new-name">Sign-in name</label><input id="new-name" name="name" autocomplete="username" required>
<label for="new-display">Your name</label><input id="new-display" name="display_name">
<label for="new-password">Password (10 characters or more)</label><input id="new-password" name="password" type="password" autocomplete="new-password" required>
<button type="submit">Make account</button></form></div>"#,
                escape(&space_name),
                hidden("action", "signup"),
            ));
    }
    page(state, "Sign in", &body)
}

pub async fn authorize_submit(
    State(state): State<AppState>,
    Form(form): Form<AuthorizeForm>,
) -> Response {
    let q = form.query.clone();
    if check_authorize(&state, &q).is_err() {
        return authorize_form(&state, &q, None).await;
    }
    let account = match form.action.as_str() {
        "signup" => sign_up(&state, &form).await,
        _ => sign_in(&state, &form).await,
    };
    match account {
        Ok(account) => complete(&state, &q, &account).await,
        Err(e) => authorize_form(&state, &q, Some(&e.message)).await,
    }
}

/// Signed in: joins the invite's space, if any, and sends the editor its one-time code.
async fn complete(state: &AppState, q: &AuthorizeQuery, account: &AccountRow) -> Response {
    if let Some(invite) = &q.invite
        && let Ok(InviteOutcome::Invalid) = state
            .store
            .accept_invite(&auth::sha256(invite), account)
            .await
    {
        tracing::info!(account = %account.id, "signed in with an invite that is no longer valid");
    }
    let code = state
        .codes
        .insert(account.id, q.code_challenge.clone(), q.redirect_uri.clone())
        .await;
    let Ok(mut target) = url::Url::parse(&q.redirect_uri) else {
        return authorize_form(state, q, None).await;
    };
    target
        .query_pairs_mut()
        .append_pair("code", &code)
        .append_pair("state", &q.state);
    Redirect::to(target.as_str()).into_response()
}

async fn sign_in(state: &AppState, form: &AuthorizeForm) -> Result<AccountRow, ApiErr> {
    let name = form.name.trim();
    if state.sign_in_limits.blocked(name).await {
        Metrics::inc(&METRICS.sign_in_blocked_total);
        return Err(ApiErr::too_many(
            "Too many wrong passwords for this name. Try again in 15 minutes.",
        ));
    }
    let account = state.store.account_by_name(name).await?;
    match account {
        Some(a)
            if a.password_hash
                .as_deref()
                .is_some_and(|h| auth::verify_password(&form.password, h)) =>
        {
            state.sign_in_limits.succeeded(name).await;
            Ok(a)
        }
        _ => {
            Metrics::inc(&METRICS.sign_in_failures_total);
            state.sign_in_limits.failed(name).await;
            // The same work whether or not the name exists.
            if account_missing(&account) {
                let _ = auth::hash_password(&form.password);
            }
            Err(ApiErr::unauthorized("The name or the password is wrong."))
        }
    }
}

fn account_missing(account: &Option<AccountRow>) -> bool {
    account
        .as_ref()
        .and_then(|a| a.password_hash.as_ref())
        .is_none()
}

async fn sign_up(state: &AppState, form: &AuthorizeForm) -> Result<AccountRow, ApiErr> {
    let invite = form
        .query
        .invite
        .as_deref()
        .ok_or_else(|| ApiErr::forbidden("New accounts need an invite link."))?;
    let (organisation, _) = state
        .store
        .invite_organisation(&auth::sha256(invite))
        .await?
        .ok_or_else(|| ApiErr::forbidden("This invite link has expired or was used up."))?;
    let name = form.name.trim();
    auth::check_name(name)?;
    auth::check_new_password(&form.password)?;
    let hash = auth::hash_password(&form.password)?;
    let display = form
        .display_name
        .as_deref()
        .map(str::trim)
        .filter(|s| !s.is_empty())
        .unwrap_or(name);
    Ok(state
        .store
        .create_account(organisation, name, display, &hash)
        .await?)
}

// ------------------------------------------------------------------- join

pub async fn join_page(State(state): State<AppState>, Path(token): Path<String>) -> Response {
    let space = state
        .store
        .invite_organisation(&auth::sha256(&token))
        .await
        .ok()
        .flatten();
    let Some((_, space_name)) = space else {
        let mut response = page(
            &state,
            "Join",
            r#"<div class="card"><h2>Join</h2><p class="error">This invite link has expired or was used up. Ask for a new one.</p></div>"#,
        );
        *response.status_mut() = StatusCode::NOT_FOUND;
        return response;
    };
    let link = |scheme: &str| {
        let mut url = url::Url::parse(&format!("{scheme}://{}/join", state.config.extension_id))
            .expect("valid base");
        url.query_pairs_mut()
            .append_pair("server", &state.config.public_url)
            .append_pair("invite", &token);
        escape(url.as_str())
    };
    let body = format!(
        r#"<div class="card"><h2>Join {space}</h2><p>You were invited to work on the model <b>{space}</b> together.</p>
<p class="muted">You need the Archify Diagram Viewer extension.</p>
<a class="button" href="{vscode}">Open in VS Code</a></div>
<div class="card"><p class="muted">Other editors: <a href="{codium}">VSCodium</a> · <a href="{cursor}">Cursor</a></p></div>"#,
        space = escape(&space_name),
        vscode = link("vscode"),
        codium = link("vscodium"),
        cursor = link("cursor"),
    );
    page(&state, "Join", &body)
}

// --------------------------------------------------------- single sign-on

pub async fn oidc_start(
    State(state): State<AppState>,
    Query(q): Query<AuthorizeQuery>,
) -> Response {
    let Some(oidc) = &state.oidc else {
        return StatusCode::NOT_FOUND.into_response();
    };
    if check_authorize(&state, &q).is_err() {
        return authorize_form(&state, &q, None).await;
    }
    match oidc.start(&state.config.public_url, q.clone()).await {
        Ok(url) => Redirect::to(&url).into_response(),
        Err(error) => {
            tracing::warn!(%error, "single sign-on did not start");
            authorize_form(
                &state,
                &q,
                Some(&format!("Single sign-on is not available: {error}.")),
            )
            .await
        }
    }
}

#[derive(Deserialize)]
pub struct CallbackQuery {
    code: Option<String>,
    state: Option<String>,
    error: Option<String>,
    error_description: Option<String>,
}

fn sso_problem(state: &AppState, message: &str) -> Response {
    let mut response = page(
        state,
        "Sign in",
        &format!(
            r#"<div class="card"><h2>Sign in for VS Code</h2>{}<p class="muted">Close this tab and sign in again from VS Code.</p></div>"#,
            error_line(Some(message))
        ),
    );
    *response.status_mut() = StatusCode::BAD_REQUEST;
    response
}

pub async fn oidc_callback(
    State(state): State<AppState>,
    Query(cb): Query<CallbackQuery>,
) -> Response {
    let Some(oidc) = &state.oidc else {
        return StatusCode::NOT_FOUND.into_response();
    };
    if let Some(error) = cb.error {
        let detail = cb.error_description.unwrap_or(error);
        return sso_problem(
            &state,
            &format!("The identity provider did not sign you in: {detail}"),
        );
    }
    let (Some(code), Some(sso_state)) = (cb.code, cb.state) else {
        return sso_problem(&state, "The identity provider sent no sign-in.");
    };
    let (q, person) = match oidc
        .finish(&state.config.public_url, &code, &sso_state)
        .await
    {
        Ok(found) => found,
        Err(error) => {
            Metrics::inc(&METRICS.sign_in_failures_total);
            tracing::warn!(%error, "single sign-on failed");
            return sso_problem(&state, &format!("Single sign-on failed: {error}."));
        }
    };
    match sso_account(&state, &q, &person).await {
        Ok(account) => {
            tracing::info!(account = %account.id, name = %account.name, "signed in through single sign-on");
            complete(&state, &q, &account).await
        }
        Err(e) => {
            Metrics::inc(&METRICS.sign_in_failures_total);
            authorize_form(&state, &q, Some(&e.message)).await
        }
    }
}

/// The account of a person the identity provider signed in: found by the
/// provider's subject, or made on the first sign-in when an invite or the
/// allowed groups let them in.
async fn sso_account(
    state: &AppState,
    q: &AuthorizeQuery,
    person: &Person,
) -> Result<AccountRow, ApiErr> {
    let config = &state.oidc.as_ref().expect("checked by the caller").config;
    if person.subject.is_empty() {
        return Err(ApiErr::unauthorized(
            "The identity provider did not say who you are.",
        ));
    }
    let admin = person.in_any(&config.admin_groups);
    if !config.allowed_groups.is_empty() && !admin && !person.in_any(&config.allowed_groups) {
        return Err(ApiErr::forbidden(format!(
            "{} signed you in, but your account there is not in a group this server allows.",
            config.label
        )));
    }
    if let Some(mut account) = state
        .store
        .account_by_identity(&config.issuer, &person.subject)
        .await?
    {
        if admin && account.role != "admin" {
            state.store.set_role(account.id, "admin").await?;
            account.role = "admin".into();
        }
        return Ok(account);
    }
    let organisation = match q.invite.as_deref() {
        Some(invite) => state
            .store
            .invite_organisation(&auth::sha256(invite))
            .await?
            .map(|(org, _)| org),
        None if !config.allowed_groups.is_empty() || admin => Some(
            state
                .store
                .organisation_or_create(&state.config.server_name)
                .await?,
        ),
        None => None,
    };
    let Some(organisation) = organisation else {
        return Err(ApiErr::forbidden(format!(
            "{} signed you in, but you have no account on this server yet. Ask someone for an invite link and open it.",
            config.label
        )));
    };
    let name = oidc::account_name(person);
    let display = person
        .display_name
        .clone()
        .or_else(|| person.username.clone())
        .unwrap_or_else(|| name.clone());
    let role = if admin { "admin" } else { "member" };
    match state
        .store
        .create_sso_account(
            organisation,
            &name,
            &display,
            role,
            &config.issuer,
            &person.subject,
            person.email.as_deref(),
        )
        .await
    {
        Ok(account) => Ok(account),
        // Two sign-ins of the same person at once: the other one made the account.
        Err(archify_sync_store::StoreError::Conflict("identity")) => state
            .store
            .account_by_identity(&config.issuer, &person.subject)
            .await?
            .ok_or_else(|| ApiErr::unauthorized("Sign in again.")),
        Err(e) => Err(e.into()),
    }
}