//! The user registry in the document: `_continuum/users/<name>`, one entry per user.
//! Protocol data, so a remake's snapshot carries it into the next epoch, and only those
//! who may write protocol data change it. No secrets: every member reads the document.
//!
//! ```json
//! { "since": 1762400000000, "by": "user:alice",
//!   "caps": { "<id>": { "path": [], "rights": ["read", "write"],
//!                       "by": "user:alice", "since": 1762400000000 } },
//!   "disabled": false }
//! ```
//!
//! Capabilities are a map by a random ID, not a list: two operators granting at once
//! both add theirs, and revoking one deletes its entry, never rewriting the others.
//! `disabled` keeps the entry (who wrote what stays readable) and gives nothing.

use std::collections::BTreeMap;

use serde_json::{Value as JsonValue, json};

use super::{Capability, Caps, Right};
use crate::document::{ReadDoc, meta, store};

/// `_continuum/users`.
pub(crate) fn users_dir() -> Vec<String> {
    meta::path(&[meta::USERS])
}

/// `_continuum/users/<name>`.
pub(crate) fn user_path(name: &str) -> Vec<String> {
    let mut path = users_dir();
    path.push(name.to_owned());
    path
}

/// Whether the swarm has a registry: until it has, every user a node lets in may do
/// what all could before (`docs/access.md`, An existing swarm).
pub(crate) fn exists(doc: &impl ReadDoc) -> bool {
    store::keys_at(doc, &users_dir()).is_ok()
}

/// The registered users' names, sorted.
pub(crate) fn names(doc: &impl ReadDoc) -> Vec<String> {
    let mut names = store::keys_at(doc, &users_dir()).unwrap_or_default();
    names.sort();
    names
}

/// A user name: what `--htpasswd` and trailers take, and a map key without `/`. 1 to 64
/// of `A-Z a-z 0-9 . _ @ -`.
pub(crate) fn valid_name(name: &str) -> bool {
    (1..=64).contains(&name.len())
        && name
            .bytes()
            .all(|b| b.is_ascii_alphanumeric() || matches!(b, b'.' | b'_' | b'@' | b'-'))
}

/// A user's entry, as read from the document. Read leniently: a field that doesn't
/// read is as if absent, and a capability that doesn't read is left out, so a damaged
/// entry gives less, never more.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub(crate) struct User {
    pub(crate) since: u64,
    pub(crate) by: String,
    pub(crate) caps: BTreeMap<String, Capability>,
    pub(crate) disabled: bool,
}

impl User {
    fn from_json(value: &JsonValue) -> Self {
        let caps = value
            .get("caps")
            .and_then(JsonValue::as_object)
            .map(|caps| {
                caps.iter()
                    .filter_map(|(id, cap)| {
                        Some((id.clone(), serde_json::from_value(cap.clone()).ok()?))
                    })
                    .collect()
            })
            .unwrap_or_default();
        Self {
            since: value.get("since").and_then(JsonValue::as_u64).unwrap_or(0),
            by: value
                .get("by")
                .and_then(JsonValue::as_str)
                .unwrap_or_default()
                .to_owned(),
            caps,
            // Anything but `false` disables: a damaged flag gives less.
            disabled: value
                .get("disabled")
                .is_some_and(|disabled| disabled != &JsonValue::Bool(false)),
        }
    }

    /// What it may do: its capabilities, none while it is disabled.
    pub(crate) fn caps(&self) -> Caps {
        if self.disabled {
            return Caps::default();
        }
        Caps::new(self.caps.values().cloned().collect())
    }
}

/// The entry of user `name`, if it has one.
pub(crate) fn user(doc: &impl ReadDoc, name: &str) -> Option<User> {
    let value = store::read_path(doc, &user_path(name)).ok()??;
    value.is_object().then(|| User::from_json(&value))
}

/// What user `name` may do: none if it isn't registered (or is disabled).
pub(crate) fn caps_of(doc: &impl ReadDoc, name: &str) -> Caps {
    user(doc, name).map(|user| user.caps()).unwrap_or_default()
}

/// A new user's entry, as written to `user_path`: granted by `by` at `since`, with
/// `caps` (each a path and its rights), each under an ID of its own (`new_id`).
pub(crate) fn entry(by: &str, since: u64, caps: &[(Vec<String>, &[Right])]) -> JsonValue {
    let caps: serde_json::Map<String, JsonValue> = caps
        .iter()
        .map(|(path, rights)| (new_id(), capability(by, since, path, rights)))
        .collect();
    json!({ "since": since, "by": by, "caps": caps, "disabled": false })
}

/// A capability as the registry records it.
pub(crate) fn capability(by: &str, since: u64, path: &[String], rights: &[Right]) -> JsonValue {
    json!({
        "path": path,
        "rights": rights.iter().map(|right| right.as_str()).collect::<Vec<_>>(),
        "by": by,
        "since": since,
    })
}

/// The first users of a new swarm, as its genesis node records them (`first_users`):
/// each name, and whether it may do everything (protocol data and managing users
/// included), not only read and write the swarm's data.
pub(crate) type FirstUsers = Vec<(String, bool)>;

/// The first users of a new swarm, from the genesis node's options: those of
/// `bootstrap_users`, each may do everything; unset, the users of its htpasswd file
/// (`htpasswd`) may read and write the swarm's data, and those of them, or of the proxy's
/// (`--user-header`), in `protocol_writers` everything. Refused if nobody could manage
/// the swarm: a registry nobody may change would lock everyone out for good.
pub(crate) fn first_users(
    bootstrap_users: &[String],
    htpasswd: &[String],
    protocol_writers: &[String],
) -> anyhow::Result<FirstUsers> {
    let mut users: BTreeMap<String, bool> = BTreeMap::new();
    if bootstrap_users.is_empty() {
        for name in htpasswd.iter().filter(|name| valid_name(name)) {
            users.insert(name.clone(), false);
        }
        for name in protocol_writers.iter().filter(|name| valid_name(name)) {
            users.insert(name.clone(), true);
        }
    } else {
        for name in bootstrap_users {
            users.insert(name.clone(), true);
        }
    }
    if !users.values().any(|admin| *admin) {
        anyhow::bail!(
            "genesis: nobody could manage the new swarm's users; name one with bootstrap-users, or put one of htpasswd's users in protocol-writers (docs/access.md)"
        );
    }
    Ok(users.into_iter().collect())
}

/// The capabilities of a first user (`first_users`): the swarm's data, and for one who
/// may do everything protocol data too.
pub(crate) fn first_caps(admin: bool) -> Vec<(Vec<String>, &'static [Right])> {
    const BOTH: &[Right] = &[Right::Read, Right::Write];
    let mut caps = vec![(Vec::new(), BOTH)];
    if admin {
        caps.push((meta::path(&[]), BOTH));
    }
    caps
}

/// A random ID for a capability (8 bytes, hex): concurrent grants don't collide.
pub(crate) fn new_id() -> String {
    let mut bytes = [0u8; 8];
    getrandom::fill(&mut bytes).expect("the system's random numbers");
    bytes.iter().map(|byte| format!("{byte:02x}")).collect()
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::document::Document;
    use crate::document::testing::change;

    fn path(text: &str) -> Vec<String> {
        text.split('/')
            .filter(|segment| !segment.is_empty())
            .map(str::to_owned)
            .collect()
    }

    #[test]
    fn names() {
        assert!(valid_name("alice"));
        assert!(valid_name("alice.smith@example.org"));
        for bad in ["", "a/b", "a:b", "a b", &"x".repeat(65)] {
            assert!(!valid_name(bad), "{bad:?}");
        }
    }

    #[test]
    fn entries_written_and_read() {
        let mut doc = Document::new();
        assert!(!exists(&doc));
        let entry = entry(
            "continuum:00",
            7,
            &[
                (vec![], &[Right::Read, Right::Write]),
                (path("_continuum"), &[Right::Read, Right::Write]),
            ],
        );
        change(&mut doc, |tx| {
            store::write_path(tx, &user_path("alice"), &entry).unwrap()
        });
        assert!(exists(&doc));
        assert_eq!(super::names(&doc), vec!["alice"]);
        let alice = user(&doc, "alice").unwrap();
        assert_eq!((alice.since, alice.by.as_str()), (7, "continuum:00"));
        assert_eq!(alice.caps.len(), 2);
        let caps = caps_of(&doc, "alice");
        assert!(caps.allows(Right::Write, &path("accounts/1")));
        assert!(caps.allows(Right::Write, &path("_continuum/users/bob")));
        assert!(caps_of(&doc, "bob").is_empty());
    }

    #[test]
    fn a_disabled_or_damaged_entry_gives_less() {
        let mut doc = Document::new();
        let mut entry = entry("x", 0, &[(vec![], &[Right::Read])]);
        entry["disabled"] = json!(true);
        change(&mut doc, |tx| {
            store::write_path(tx, &user_path("carol"), &entry).unwrap()
        });
        assert!(user(&doc, "carol").is_some());
        assert!(caps_of(&doc, "carol").is_empty());

        let damaged = json!({
            "caps": { "a": { "path": "not a list", "rights": ["read"] },
                      "b": { "path": ["notes"], "rights": ["read"] } },
            "disabled": "no"
        });
        change(&mut doc, |tx| {
            store::write_path(tx, &user_path("dave"), &damaged).unwrap()
        });
        let dave = user(&doc, "dave").unwrap();
        assert_eq!(dave.caps.len(), 1);
        assert!(dave.disabled);
        assert!(dave.caps().is_empty());
    }

    #[test]
    fn the_first_users() {
        let names = |list: &[&str]| list.iter().map(|n| (*n).to_owned()).collect::<Vec<_>>();
        assert_eq!(
            first_users(&[], &names(&["alice", "bob"]), &names(&["alice"])).unwrap(),
            vec![("alice".to_owned(), true), ("bob".to_owned(), false)]
        );
        // A protocol writer the proxy names, not in htpasswd.
        assert_eq!(
            first_users(&[], &names(&["bob"]), &names(&["carol"])).unwrap(),
            vec![("bob".to_owned(), false), ("carol".to_owned(), true)]
        );
        assert_eq!(
            first_users(&names(&["root"]), &names(&["alice"]), &names(&["alice"])).unwrap(),
            vec![("root".to_owned(), true)]
        );
        assert!(first_users(&[], &names(&["alice"]), &[]).is_err());
        assert!(first_users(&[], &[], &[]).is_err());
        let admin = Caps::new(
            first_caps(true)
                .into_iter()
                .map(|(path, rights)| {
                    serde_json::from_value(capability("x", 0, &path, rights)).unwrap()
                })
                .collect(),
        );
        assert!(admin.allows(Right::Write, &path("_continuum/users/x")));
        assert!(admin.allows(Right::Write, &path("accounts")));
        let user = Caps::new(
            first_caps(false)
                .into_iter()
                .map(|(path, rights)| {
                    serde_json::from_value(capability("x", 0, &path, rights)).unwrap()
                })
                .collect(),
        );
        assert!(user.allows(Right::Write, &path("accounts")));
        assert!(!user.allows(Right::Read, &path("_continuum")));
    }

    #[test]
    fn concurrent_grants_both_hold() {
        let mut ours = Document::new();
        let entry = entry("x", 0, &[]);
        change(&mut ours, |tx| {
            store::write_path(tx, &user_path("erin"), &entry).unwrap()
        });
        let mut theirs = ours.fork();
        for (doc, at) in [(&mut ours, "notes"), (&mut theirs, "logs")] {
            let mut cap_path = user_path("erin");
            cap_path.extend(["caps".to_owned(), new_id()]);
            let cap = capability("x", 0, &path(at), &[Right::Read]);
            change(doc, |tx| store::write_path(tx, &cap_path, &cap).unwrap());
        }
        ours.merge(&mut theirs).unwrap();
        let caps = caps_of(&ours, "erin");
        assert!(caps.allows(Right::Read, &path("notes")));
        assert!(caps.allows(Right::Read, &path("logs")));
    }
}