//! `/admin/users`: the swarm's users and what each may do (`access.md`), managed
//! through the API rather than by writing the registry's entries through the store.
//!
//! * `GET /admin/users`: every user, its entry and whether it may manage users.
//! * `GET /admin/users/{name}`: one.
//! * `POST /admin/users/{name}`: adds a user, with the capabilities of the body
//!   (`{"caps": [{"path": [...], "rights": ["read", "write"]}, …]}`, none if absent);
//!   `409` if it exists.
//! * `DELETE /admin/users/{name}`: removes a user (`disabled` keeps who wrote what
//!   readable: usually the better choice).
//! * `PUT /admin/users/{name}/disabled`: `true` or `false`.
//! * `POST /admin/users/{name}/caps`: grants a capability (`{"path": […], "rights":
//!   […]}`), answered with its ID; `DELETE /admin/users/{name}/caps/{id}` revokes one.
//! * `POST /admin/users`: adds several at once, by name, each with the capabilities
//!   `POST /admin/users/{name}` takes (`{"alice": {"caps": […]}, "bob": {…}}`); `409` if
//!   one exists. How a swarm without a registry gets one, the caller among those who
//!   may manage users.
//!
//! Looking needs `read` on `_continuum/users`, changing `write` on it (in a swarm
//! without a registry, being in `--protocol-writers`). Every change is one change to
//! the document, logged, named by who made it, and refused (`409`) where it would lock
//! its maker out (`access::registry_kept`).

use axum::{
    Extension, Json,
    extract::{Path, State},
    http::StatusCode,
    response::{IntoResponse, Response},
};
use serde::Deserialize;
use serde_json::{Value as JsonValue, json};
use tracing::info;

use super::ApiError;
use super::access::{Access, Before, registry_kept};
use super::auth::AuthenticatedUser;
use crate::access::{Right, registry};
use crate::document::store;
use crate::state::AppState;

/// A capability as a request gives it.
#[derive(Debug, Deserialize)]
#[serde(deny_unknown_fields)]
pub(crate) struct CapRequest {
    path: Vec<String>,
    rights: Vec<String>,
}

impl CapRequest {
    fn rights(&self) -> Result<Vec<Right>, ApiError> {
        if self.rights.is_empty() {
            return Err(bad("a capability gives at least one right"));
        }
        self.rights
            .iter()
            .map(|right| match right.as_str() {
                "read" => Ok(Right::Read),
                "write" => Ok(Right::Write),
                other => Err(bad(&format!("no right {other:?}: read or write"))),
            })
            .collect()
    }
}

#[derive(Debug, Default, Deserialize)]
#[serde(deny_unknown_fields)]
pub(crate) struct AddRequest {
    #[serde(default)]
    caps: Vec<CapRequest>,
}

fn bad(message: &str) -> ApiError {
    ApiError(StatusCode::BAD_REQUEST, Some(message.to_owned()))
}

fn named(name: &str) -> Result<(), ApiError> {
    if registry::valid_name(name) {
        Ok(())
    } else {
        Err(bad("not a user name: 1 to 64 of A-Z a-z 0-9 . _ @ -"))
    }
}

/// `403` unless the caller may change the registry: `write` on `_continuum/users`, or
/// in a swarm without a registry, being in `--protocol-writers` (as for writes to
/// protocol data through the store).
fn may_manage(state: &AppState, user: &str, access: &Access) -> Result<(), ApiError> {
    let allowed = match access {
        Access::Everything => state.protocol_writers.contains(user),
        Access::Caps(caps) => caps.allows(Right::Write, &registry::users_dir()),
    };
    if allowed {
        Ok(())
    } else {
        Err(ApiError(
            StatusCode::FORBIDDEN,
            Some("may not manage users (docs/access.md)".to_owned()),
        ))
    }
}

/// A user's entry as the API shows it: as recorded, and whether it may manage users.
fn shown(doc: &impl crate::document::ReadDoc, name: &str) -> Option<JsonValue> {
    let mut entry = store::read_path(doc, &registry::user_path(name)).ok()??;
    let manages = registry::caps_of(doc, name).allows(Right::Write, &registry::users_dir());
    if let Some(object) = entry.as_object_mut() {
        object.insert("name".to_owned(), json!(name));
        object.insert("manages".to_owned(), json!(manages));
    }
    Some(entry)
}

/// `GET /admin/users`.
pub(crate) async fn list(State(state): State<AppState>) -> Json<JsonValue> {
    let replica = state.doc.read().await;
    let users: Vec<JsonValue> = registry::names(&replica.doc)
        .iter()
        .filter_map(|name| shown(&replica.doc, name))
        .collect();
    Json(json!({ "registry": registry::exists(&replica.doc), "users": users }))
}

/// `GET /admin/users/{name}`.
pub(crate) async fn get(
    State(state): State<AppState>,
    Path(name): Path<String>,
) -> Result<Json<JsonValue>, ApiError> {
    let replica = state.doc.read().await;
    shown(&replica.doc, &name)
        .map(Json)
        .ok_or(ApiError(StatusCode::NOT_FOUND, None))
}

/// Writes to the registry what `f` writes, as `user`, logged as `what`: one change,
/// dropped whole if it fails or would lock `user` out (`registry_kept`).
async fn change(
    state: &AppState,
    user: &str,
    what: String,
    f: impl FnOnce(&mut crate::document::Transaction<'_>, &str, u64) -> Result<(), ApiError>
    + Send
    + 'static,
) -> Result<(), ApiError> {
    if !state.is_ready().await {
        return Err(StatusCode::SERVICE_UNAVAILABLE.into());
    }
    let by = format!("user:{user}");
    let writer = user.to_owned();
    let since = state.clock.now_millis().as_u64();
    state
        .mutate_doc_for(Some(user.to_owned()), move |doc| {
            let before = Before::of(&*doc, &writer);
            f(doc, &by, since)?;
            registry_kept(&*doc, &registry::users_dir(), before, &writer)
        })
        .await?;
    info!(user = %user, "{what}");
    Ok(())
}

/// `POST /admin/users/{name}`.
pub(crate) async fn add(
    State(state): State<AppState>,
    Extension(user): Extension<AuthenticatedUser>,
    Extension(access): Extension<Access>,
    Path(name): Path<String>,
    body: Option<Json<AddRequest>>,
) -> Result<Response, ApiError> {
    may_manage(&state, &user.0, &access)?;
    named(&name)?;
    let request = body.map(|Json(request)| request).unwrap_or_default();
    let caps: Vec<(Vec<String>, Vec<Right>)> = request
        .caps
        .iter()
        .map(|cap| Ok((cap.path.clone(), cap.rights()?)))
        .collect::<Result<_, ApiError>>()?;
    let path = registry::user_path(&name);
    change(
        &state,
        &user.0,
        format!("Added user {name}"),
        move |doc, by, since| {
            if store::read_path(&*doc, &path)?.is_some() {
                return Err(ApiError(
                    StatusCode::CONFLICT,
                    Some("the user exists".to_owned()),
                ));
            }
            let caps: Vec<(Vec<String>, &[Right])> = caps
                .iter()
                .map(|(path, rights)| (path.clone(), rights.as_slice()))
                .collect();
            store::write_path(doc, &path, &registry::entry(by, since, &caps))?;
            Ok(())
        },
    )
    .await?;
    Ok(StatusCode::CREATED.into_response())
}

/// `DELETE /admin/users/{name}`.
pub(crate) async fn remove(
    State(state): State<AppState>,
    Extension(user): Extension<AuthenticatedUser>,
    Extension(access): Extension<Access>,
    Path(name): Path<String>,
) -> Result<StatusCode, ApiError> {
    may_manage(&state, &user.0, &access)?;
    let path = registry::user_path(&name);
    change(
        &state,
        &user.0,
        format!("Removed user {name}"),
        move |doc, _, _| {
            store::delete_path(doc, &path, false)?;
            Ok(())
        },
    )
    .await?;
    Ok(StatusCode::NO_CONTENT)
}

/// `PUT /admin/users/{name}/disabled`.
pub(crate) async fn set_disabled(
    State(state): State<AppState>,
    Extension(user): Extension<AuthenticatedUser>,
    Extension(access): Extension<Access>,
    Path(name): Path<String>,
    Json(disabled): Json<bool>,
) -> Result<StatusCode, ApiError> {
    may_manage(&state, &user.0, &access)?;
    let entry = registry::user_path(&name);
    let what = format!(
        "{} user {name}",
        if disabled { "Disabled" } else { "Enabled" }
    );
    change(&state, &user.0, what, move |doc, _, _| {
        if store::read_path(&*doc, &entry)?.is_none() {
            return Err(ApiError(StatusCode::NOT_FOUND, None));
        }
        let mut path = entry;
        path.push("disabled".to_owned());
        store::write_path(doc, &path, &json!(disabled))?;
        Ok(())
    })
    .await?;
    Ok(StatusCode::NO_CONTENT)
}

/// `POST /admin/users/{name}/caps`.
pub(crate) async fn grant(
    State(state): State<AppState>,
    Extension(user): Extension<AuthenticatedUser>,
    Extension(access): Extension<Access>,
    Path(name): Path<String>,
    Json(cap): Json<CapRequest>,
) -> Result<Response, ApiError> {
    may_manage(&state, &user.0, &access)?;
    let rights = cap.rights()?;
    let id = registry::new_id();
    let entry = registry::user_path(&name);
    let mut path = entry.clone();
    path.extend(["caps".to_owned(), id.clone()]);
    let what = format!("Granted user {name} {:?} on {:?}", cap.rights, cap.path);
    change(&state, &user.0, what, move |doc, by, since| {
        if store::read_path(&*doc, &entry)?.is_none() {
            return Err(ApiError(StatusCode::NOT_FOUND, None));
        }
        store::write_path(
            doc,
            &path,
            &registry::capability(by, since, &cap.path, &rights),
        )?;
        Ok(())
    })
    .await?;
    Ok((StatusCode::CREATED, Json(json!({ "id": id }))).into_response())
}

/// `DELETE /admin/users/{name}/caps/{id}`.
pub(crate) async fn revoke(
    State(state): State<AppState>,
    Extension(user): Extension<AuthenticatedUser>,
    Extension(access): Extension<Access>,
    Path((name, id)): Path<(String, String)>,
) -> Result<StatusCode, ApiError> {
    may_manage(&state, &user.0, &access)?;
    let mut path = registry::user_path(&name);
    path.extend(["caps".to_owned(), id.clone()]);
    change(
        &state,
        &user.0,
        format!("Revoked capability {id} of user {name}"),
        move |doc, _, _| {
            store::delete_path(doc, &path, false)?;
            Ok(())
        },
    )
    .await?;
    Ok(StatusCode::NO_CONTENT)
}

/// `POST /admin/users`.
pub(crate) async fn add_several(
    State(state): State<AppState>,
    Extension(user): Extension<AuthenticatedUser>,
    Extension(access): Extension<Access>,
    Json(request): Json<std::collections::BTreeMap<String, AddRequest>>,
) -> Result<StatusCode, ApiError> {
    may_manage(&state, &user.0, &access)?;
    if request.is_empty() {
        return Err(bad("nobody to add"));
    }
    let mut users = Vec::new();
    for (name, add) in &request {
        named(name)?;
        let caps: Vec<(Vec<String>, Vec<Right>)> = add
            .caps
            .iter()
            .map(|cap| Ok((cap.path.clone(), cap.rights()?)))
            .collect::<Result<_, ApiError>>()?;
        users.push((name.clone(), caps));
    }
    let what = format!("Added users {:?}", request.keys().collect::<Vec<_>>());
    change(&state, &user.0, what, move |doc, by, since| {
        for (name, caps) in &users {
            let path = registry::user_path(name);
            if store::read_path(&*doc, &path)?.is_some() {
                return Err(ApiError(
                    StatusCode::CONFLICT,
                    Some(format!("user {name} exists")),
                ));
            }
            let caps: Vec<(Vec<String>, &[Right])> = caps
                .iter()
                .map(|(path, rights)| (path.clone(), rights.as_slice()))
                .collect();
            store::write_path(doc, &path, &registry::entry(by, since, &caps))?;
        }
        Ok(())
    })
    .await?;
    Ok(StatusCode::CREATED)
}