allowthem-core 0.0.5

use base64ct::{Base64UrlUnpadded, Encoding};
use chrono::{DateTime, Duration, Utc};
use rand::TryRngCore;
use rand::rngs::OsRng;
use sha2::{Digest, Sha256};

use serde::Serialize;

use crate::db::Db;
use crate::error::AuthError;
use crate::types::{Email, Session, SessionId, SessionToken, TokenHash, UserId};

/// Configuration for session lifecycle and cookie generation.
pub struct SessionConfig {
    /// How long a session lives. Default: 24 hours.
    pub ttl: Duration,
    /// Name of the session cookie. Default: `"allowthem_session"`.
    pub cookie_name: &'static str,
    /// Whether to set the `Secure` attribute on the cookie.
    /// Should be `true` in production (HTTPS), `false` in local dev.
    pub secure: bool,
}

impl Default for SessionConfig {
    fn default() -> Self {
        Self {
            ttl: Duration::hours(24),
            cookie_name: "allowthem_session",
            secure: true,
        }
    }
}

/// A session with joined user email, for admin list display.
/// Omits `token_hash` — the admin UI must never expose session tokens.
#[derive(Debug, Clone, Serialize, sqlx::FromRow)]
pub struct SessionListEntry {
    pub id: SessionId,
    pub user_id: UserId,
    pub user_email: Email,
    pub ip_address: Option<String>,
    pub user_agent: Option<String>,
    pub expires_at: DateTime<Utc>,
    pub created_at: DateTime<Utc>,
}

/// Parameters for listing sessions in the admin session viewer.
pub struct ListSessionsParams {
    pub user_id: Option<UserId>,
    pub limit: u32,
    pub offset: u32,
}

/// Result of a paginated session list.
pub struct ListSessionsResult {
    pub sessions: Vec<SessionListEntry>,
    pub total: u32,
}

/// Generate a cryptographically random session token.
///
/// Fills 32 bytes from the OS random source and encodes them as base64url
/// without padding, producing a 43-character string.
pub fn generate_token() -> SessionToken {
    let mut bytes = [0u8; 32];
    OsRng
        .try_fill_bytes(&mut bytes)
        .expect("OS RNG unavailable");
    SessionToken::from_encoded(Base64UrlUnpadded::encode_string(&bytes))
}

/// Hash a session token with SHA-256.
///
/// The resulting hex string (64 chars) is what is stored in the database.
/// The raw token is never persisted.
pub fn hash_token(token: &SessionToken) -> TokenHash {
    let digest = Sha256::digest(token.as_str().as_bytes());
    TokenHash::new_unchecked(format!("{digest:x}"))
}

impl Db {
    /// Insert a new session record and return it.
    ///
    /// The caller is responsible for hashing the token before calling this function
    /// via `hash_token()`. The raw token must never be passed here.
    pub async fn create_session(
        &self,
        user_id: UserId,
        token_hash: TokenHash,
        ip_address: Option<&str>,
        user_agent: Option<&str>,
        expires_at: DateTime<Utc>,
    ) -> Result<Session, AuthError> {
        let id = SessionId::new();
        let expires_at_str = expires_at.format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string();
        sqlx::query_as::<_, Session>(
            "INSERT INTO allowthem_sessions (id, token_hash, user_id, ip_address, user_agent, expires_at)
             VALUES (?, ?, ?, ?, ?, ?)
             RETURNING id, token_hash, user_id, ip_address, user_agent, expires_at, created_at",
        )
        .bind(id)
        .bind(token_hash)
        .bind(user_id)
        .bind(ip_address)
        .bind(user_agent)
        .bind(expires_at_str)
        .fetch_one(self.pool())
        .await
        .map_err(AuthError::Database)
    }

    /// Look up a session by raw token.
    ///
    /// Hashes the token internally and queries by hash. Expired sessions
    /// (where `expires_at` is in the past) are excluded. Returns `None`
    /// when no matching active session is found.
    pub async fn lookup_session(&self, token: &SessionToken) -> Result<Option<Session>, AuthError> {
        let hash = hash_token(token);
        let now = Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string();
        sqlx::query_as::<_, Session>(
            "SELECT id, token_hash, user_id, ip_address, user_agent, expires_at, created_at
             FROM allowthem_sessions
             WHERE token_hash = ? AND expires_at > ?",
        )
        .bind(hash)
        .bind(now)
        .fetch_optional(self.pool())
        .await
        .map_err(AuthError::Database)
    }

    /// Validate a session token and optionally extend it.
    ///
    /// Fetches the active session by token hash. If the session is past the
    /// halfway point of its TTL (`now > expires_at - ttl/2`), it is renewed
    /// by setting `expires_at = now + ttl`. Returns the session with the
    /// updated expiry, or `None` if no active session was found.
    pub async fn validate_session(
        &self,
        token: &SessionToken,
        ttl: Duration,
    ) -> Result<Option<Session>, AuthError> {
        let session = match self.lookup_session(token).await? {
            Some(s) => s,
            None => return Ok(None),
        };

        let now = Utc::now();
        let halfway = session.expires_at - ttl / 2;

        if now > halfway {
            let new_expires_at = now + ttl;
            let new_expires_str = new_expires_at.format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string();
            let hash = hash_token(token);
            sqlx::query("UPDATE allowthem_sessions SET expires_at = ? WHERE token_hash = ?")
                .bind(&new_expires_str)
                .bind(hash)
                .execute(self.pool())
                .await
                .map_err(AuthError::Database)?;

            return Ok(Some(Session {
                expires_at: new_expires_at,
                ..session
            }));
        }

        Ok(Some(session))
    }

    /// Delete a single session by raw token.
    ///
    /// Returns `true` if a session was found and deleted, `false` if no
    /// matching session existed.
    pub async fn delete_session(&self, token: &SessionToken) -> Result<bool, AuthError> {
        let hash = hash_token(token);
        let result = sqlx::query("DELETE FROM allowthem_sessions WHERE token_hash = ?")
            .bind(hash)
            .execute(self.pool())
            .await
            .map_err(AuthError::Database)?;
        Ok(result.rows_affected() > 0)
    }

    /// Delete all sessions for a user.
    ///
    /// Returns the number of sessions that were deleted.
    pub async fn delete_user_sessions(&self, user_id: &UserId) -> Result<u64, AuthError> {
        let result = sqlx::query("DELETE FROM allowthem_sessions WHERE user_id = ?")
            .bind(*user_id)
            .execute(self.pool())
            .await
            .map_err(AuthError::Database)?;
        Ok(result.rows_affected())
    }

    /// List all active (non-expired) sessions for a user.
    ///
    /// Returns sessions ordered by `created_at` descending (newest first).
    pub async fn list_user_sessions(&self, user_id: UserId) -> Result<Vec<Session>, AuthError> {
        let now = Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string();
        sqlx::query_as::<_, Session>(
            "SELECT id, token_hash, user_id, ip_address, user_agent, expires_at, created_at \
             FROM allowthem_sessions \
             WHERE user_id = ? AND expires_at > ? \
             ORDER BY created_at DESC",
        )
        .bind(user_id)
        .bind(now)
        .fetch_all(self.pool())
        .await
        .map_err(AuthError::Database)
    }

    /// List all active sessions with user email, for admin session viewer.
    ///
    /// Joins sessions with users. Filters to non-expired sessions only.
    /// Optional user_id filter. Two static query variants (no dynamic SQL).
    pub async fn list_all_sessions(
        &self,
        params: ListSessionsParams,
    ) -> Result<ListSessionsResult, AuthError> {
        let now = Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string();

        if let Some(user_id) = params.user_id {
            let total = sqlx::query_scalar::<_, i64>(
                "SELECT COUNT(*) FROM allowthem_sessions s \
                 JOIN allowthem_users u ON s.user_id = u.id \
                 WHERE s.expires_at > ? AND s.user_id = ?",
            )
            .bind(&now)
            .bind(user_id)
            .fetch_one(self.pool())
            .await
            .map_err(AuthError::Database)? as u32;

            let sessions = sqlx::query_as::<_, SessionListEntry>(
                "SELECT s.id, s.user_id, u.email AS user_email, \
                 s.ip_address, s.user_agent, s.expires_at, s.created_at \
                 FROM allowthem_sessions s \
                 JOIN allowthem_users u ON s.user_id = u.id \
                 WHERE s.expires_at > ? AND s.user_id = ? \
                 ORDER BY s.created_at DESC \
                 LIMIT ? OFFSET ?",
            )
            .bind(&now)
            .bind(user_id)
            .bind(params.limit)
            .bind(params.offset)
            .fetch_all(self.pool())
            .await
            .map_err(AuthError::Database)?;

            Ok(ListSessionsResult { sessions, total })
        } else {
            let total = sqlx::query_scalar::<_, i64>(
                "SELECT COUNT(*) FROM allowthem_sessions s \
                 JOIN allowthem_users u ON s.user_id = u.id \
                 WHERE s.expires_at > ?",
            )
            .bind(&now)
            .fetch_one(self.pool())
            .await
            .map_err(AuthError::Database)? as u32;

            let sessions = sqlx::query_as::<_, SessionListEntry>(
                "SELECT s.id, s.user_id, u.email AS user_email, \
                 s.ip_address, s.user_agent, s.expires_at, s.created_at \
                 FROM allowthem_sessions s \
                 JOIN allowthem_users u ON s.user_id = u.id \
                 WHERE s.expires_at > ? \
                 ORDER BY s.created_at DESC \
                 LIMIT ? OFFSET ?",
            )
            .bind(&now)
            .bind(params.limit)
            .bind(params.offset)
            .fetch_all(self.pool())
            .await
            .map_err(AuthError::Database)?;

            Ok(ListSessionsResult { sessions, total })
        }
    }

    /// Delete a single session by primary key.
    ///
    /// Used by the admin session viewer to revoke individual sessions.
    /// Returns `true` if a session was found and deleted, `false` if not.
    pub async fn delete_session_by_id(&self, id: SessionId) -> Result<bool, AuthError> {
        let result = sqlx::query("DELETE FROM allowthem_sessions WHERE id = ?")
            .bind(id)
            .execute(self.pool())
            .await
            .map_err(AuthError::Database)?;
        Ok(result.rows_affected() > 0)
    }
}

/// Build a `Set-Cookie` header value for the given session token.
///
/// Attributes: `HttpOnly`, `SameSite=Lax`, `Path=/`, `Max-Age` derived from
/// `config.ttl`. The `Secure` attribute is added only when `config.secure` is
/// `true`. The `Domain` attribute is omitted when `domain` is empty.
pub fn session_cookie(token: &SessionToken, config: &SessionConfig, domain: &str) -> String {
    let max_age = config.ttl.num_seconds();
    let mut cookie = format!(
        "{}={}; HttpOnly; SameSite=Lax; Path=/; Max-Age={}",
        config.cookie_name,
        token.as_str(),
        max_age,
    );
    if !domain.is_empty() {
        cookie.push_str("; Domain=");
        cookie.push_str(domain);
    }
    if config.secure {
        cookie.push_str("; Secure");
    }
    cookie
}

/// Build a `Set-Cookie` header value that expires the session cookie.
///
/// Returns `Max-Age=0` with the same cookie name, path, domain, and flags
/// as `session_cookie()` so the browser matches and removes the stored cookie.
pub fn clear_session_cookie(config: &SessionConfig, domain: &str) -> String {
    let mut cookie = format!(
        "{}=; HttpOnly; SameSite=Lax; Path=/; Max-Age=0",
        config.cookie_name,
    );
    if !domain.is_empty() {
        cookie.push_str("; Domain=");
        cookie.push_str(domain);
    }
    if config.secure {
        cookie.push_str("; Secure");
    }
    cookie
}

/// Extract the session token from a `Cookie` header value.
///
/// Searches the semicolon-separated list of `name=value` pairs for
/// `cookie_name`. Returns `None` if the cookie is absent.
pub fn parse_session_cookie(cookie_header: &str, cookie_name: &str) -> Option<SessionToken> {
    for pair in cookie_header.split("; ") {
        if let Some((name, value)) = pair.split_once('=')
            && name.trim() == cookie_name
        {
            return Some(SessionToken::from_encoded(value.trim().to_string()));
        }
    }
    None
}