use std::collections::{BTreeMap, BTreeSet, HashMap};
use std::io::Write;
use std::path::{Path, PathBuf};
use std::str::FromStr;
use std::sync::{Arc, RwLock};

use anyhow::{bail, Error};

use lazy_static::lazy_static;

use ::serde::{Deserialize, Serialize};
use serde::de::{value, IntoDeserializer};

use proxmox::api::{api, schema::*};
use proxmox::constnamedbitmap;
use proxmox::tools::{fs::replace_file, fs::CreateOptions};

use crate::api2::types::{Authid, Userid};

// define Privilege bitfield

constnamedbitmap! {
    /// Contains a list of privilege name to privilege value mappings.
    ///
    /// The names are used when displaying/persisting privileges anywhere, the values are used to
    /// allow easy matching of privileges as bitflags.
    PRIVILEGES: u64 => {
        /// Sys.Audit allows knowing about the system and its status
        PRIV_SYS_AUDIT("Sys.Audit");
        /// Sys.Modify allows modifying system-level configuration
        PRIV_SYS_MODIFY("Sys.Modify");
        /// Sys.Modify allows to poweroff/reboot/.. the system
        PRIV_SYS_POWER_MANAGEMENT("Sys.PowerManagement");

        /// Datastore.Audit allows knowing about a datastore,
        /// including reading the configuration entry and listing its contents
        PRIV_DATASTORE_AUDIT("Datastore.Audit");
        /// Datastore.Allocate allows creating or deleting datastores
        PRIV_DATASTORE_ALLOCATE("Datastore.Allocate");
        /// Datastore.Modify allows modifying a datastore and its contents
        PRIV_DATASTORE_MODIFY("Datastore.Modify");
        /// Datastore.Read allows reading arbitrary backup contents
        PRIV_DATASTORE_READ("Datastore.Read");
        /// Allows verifying a datastore
        PRIV_DATASTORE_VERIFY("Datastore.Verify");

        /// Datastore.Backup allows Datastore.Read|Verify and creating new snapshots,
        /// but also requires backup ownership
        PRIV_DATASTORE_BACKUP("Datastore.Backup");
        /// Datastore.Prune allows deleting snapshots,
        /// but also requires backup ownership
        PRIV_DATASTORE_PRUNE("Datastore.Prune");

        /// Permissions.Modify allows modifying ACLs
        PRIV_PERMISSIONS_MODIFY("Permissions.Modify");

        /// Remote.Audit allows reading remote.cfg and sync.cfg entries
        PRIV_REMOTE_AUDIT("Remote.Audit");
        /// Remote.Modify allows modifying remote.cfg
        PRIV_REMOTE_MODIFY("Remote.Modify");
        /// Remote.Read allows reading data from a configured `Remote`
        PRIV_REMOTE_READ("Remote.Read");

        /// Sys.Console allows access to the system's console
        PRIV_SYS_CONSOLE("Sys.Console");
    }
}

/// Admin always has all privileges. It can do everything except a few actions
/// which are limited to the 'root@pam` superuser
pub const ROLE_ADMIN: u64 = std::u64::MAX;

/// NoAccess can be used to remove privileges from specific (sub-)paths
pub const ROLE_NO_ACCESS: u64 = 0;

#[rustfmt::skip]
/// Audit can view configuration and status information, but not modify it.
pub const ROLE_AUDIT: u64 = 0
    | PRIV_SYS_AUDIT
    | PRIV_DATASTORE_AUDIT;

#[rustfmt::skip]
/// Datastore.Admin can do anything on the datastore.
pub const ROLE_DATASTORE_ADMIN: u64 = 0
    | PRIV_DATASTORE_AUDIT
    | PRIV_DATASTORE_MODIFY
    | PRIV_DATASTORE_READ
    | PRIV_DATASTORE_VERIFY
    | PRIV_DATASTORE_BACKUP
    | PRIV_DATASTORE_PRUNE;

#[rustfmt::skip]
/// Datastore.Reader can read/verify datastore content and do restore
pub const ROLE_DATASTORE_READER: u64 = 0
    | PRIV_DATASTORE_AUDIT
    | PRIV_DATASTORE_VERIFY
    | PRIV_DATASTORE_READ;

#[rustfmt::skip]
/// Datastore.Backup can do backup and restore, but no prune.
pub const ROLE_DATASTORE_BACKUP: u64 = 0
    | PRIV_DATASTORE_BACKUP;

#[rustfmt::skip]
/// Datastore.PowerUser can do backup, restore, and prune.
pub const ROLE_DATASTORE_POWERUSER: u64 = 0
    | PRIV_DATASTORE_PRUNE
    | PRIV_DATASTORE_BACKUP;

#[rustfmt::skip]
/// Datastore.Audit can audit the datastore.
pub const ROLE_DATASTORE_AUDIT: u64 = 0
    | PRIV_DATASTORE_AUDIT;

#[rustfmt::skip]
/// Remote.Audit can audit the remote
pub const ROLE_REMOTE_AUDIT: u64 = 0
    | PRIV_REMOTE_AUDIT;

#[rustfmt::skip]
/// Remote.Admin can do anything on the remote.
pub const ROLE_REMOTE_ADMIN: u64 = 0
    | PRIV_REMOTE_AUDIT
    | PRIV_REMOTE_MODIFY
    | PRIV_REMOTE_READ;

#[rustfmt::skip]
/// Remote.SyncOperator can do read and prune on the remote.
pub const ROLE_REMOTE_SYNC_OPERATOR: u64 = 0
    | PRIV_REMOTE_AUDIT
    | PRIV_REMOTE_READ;

/// NoAccess can be used to remove privileges from specific (sub-)paths
pub const ROLE_NAME_NO_ACCESS: &str = "NoAccess";

#[api()]
#[repr(u64)]
#[derive(Serialize, Deserialize)]
/// Enum representing roles via their [PRIVILEGES] combination.
///
/// Since privileges are implemented as bitflags, each unique combination of privileges maps to a
/// single, unique `u64` value that is used in this enum definition.
pub enum Role {
    /// Administrator
    Admin = ROLE_ADMIN,
    /// Auditor
    Audit = ROLE_AUDIT,
    /// Disable Access
    NoAccess = ROLE_NO_ACCESS,
    /// Datastore Administrator
    DatastoreAdmin = ROLE_DATASTORE_ADMIN,
    /// Datastore Reader (inspect datastore content and do restores)
    DatastoreReader = ROLE_DATASTORE_READER,
    /// Datastore Backup (backup and restore owned backups)
    DatastoreBackup = ROLE_DATASTORE_BACKUP,
    /// Datastore PowerUser (backup, restore and prune owned backup)
    DatastorePowerUser = ROLE_DATASTORE_POWERUSER,
    /// Datastore Auditor
    DatastoreAudit = ROLE_DATASTORE_AUDIT,
    /// Remote Auditor
    RemoteAudit = ROLE_REMOTE_AUDIT,
    /// Remote Administrator
    RemoteAdmin = ROLE_REMOTE_ADMIN,
    /// Syncronisation Opertator
    RemoteSyncOperator = ROLE_REMOTE_SYNC_OPERATOR,
}

impl FromStr for Role {
    type Err = value::Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Self::deserialize(s.into_deserializer())
    }
}

lazy_static! {
    /// Map of pre-defined [Roles](Role) to their associated [privileges](PRIVILEGES) combination and
    /// description.
    pub static ref ROLE_NAMES: HashMap<&'static str, (u64, &'static str)> = {
        let mut map = HashMap::new();

        let list = match Role::API_SCHEMA {
            Schema::String(StringSchema { format: Some(ApiStringFormat::Enum(list)), .. }) => list,
            _ => unreachable!(),
        };

        for entry in list.iter() {
            let privs: u64 = Role::from_str(entry.value).unwrap() as u64;
            map.insert(entry.value, (privs, entry.description));
        }

        map
    };
}

pub(crate) fn split_acl_path(path: &str) -> Vec<&str> {
    let items = path.split('/');

    let mut components = vec![];

    for name in items {
        if name.is_empty() {
            continue;
        }
        components.push(name);
    }

    components
}

/// Check whether a given ACL `path` conforms to the expected schema.
///
/// Currently this just checks for the number of components for various sub-trees.
pub fn check_acl_path(path: &str) -> Result<(), Error> {
    let components = split_acl_path(path);

    let components_len = components.len();

    if components_len == 0 {
        return Ok(());
    }
    match components[0] {
        "access" => {
            if components_len == 1 {
                return Ok(());
            }
            match components[1] {
                "acl" | "users" => {
                    if components_len == 2 {
                        return Ok(());
                    }
                }
                _ => {}
            }
        }
        "datastore" => {
            // /datastore/{store}
            if components_len <= 2 {
                return Ok(());
            }
        }
        "remote" => {
            // /remote/{remote}/{store}
            if components_len <= 3 {
                return Ok(());
            }
        }
        "system" => {
            if components_len == 1 {
                return Ok(());
            }
            match components[1] {
                "disks" | "log" | "status" | "tasks" | "time" => {
                    if components_len == 2 {
                        return Ok(());
                    }
                }
                "services" => {
                    // /system/services/{service}
                    if components_len <= 3 {
                        return Ok(());
                    }
                }
                "network" => {
                    if components_len == 2 {
                        return Ok(());
                    }
                    match components[2] {
                        "dns" => {
                            if components_len == 3 {
                                return Ok(());
                            }
                        }
                        "interfaces" => {
                            // /system/network/interfaces/{iface}
                            if components_len <= 4 {
                                return Ok(());
                            }
                        }
                        _ => {}
                    }
                }
                _ => {}
            }
        }
        _ => {}
    }

    bail!("invalid acl path '{}'.", path);
}

/// Tree representing a parsed acl.cfg
pub struct AclTree {
    /// Root node of the tree.
    ///
    /// The rest of the tree is available via [find_node()](AclTree::find_node()) or an
    /// [AclTreeNode]'s [children](AclTreeNode::children) member.
    pub root: AclTreeNode,
}

/// Node representing ACLs for a certain ACL path.
pub struct AclTreeNode {
    /// [User](crate::config::user::User) or
    /// [Token](crate::config::user::ApiToken) ACLs for this node.
    pub users: HashMap<Authid, HashMap<String, bool>>,
    /// `Group` ACLs for this node (not yet implemented)
    pub groups: HashMap<String, HashMap<String, bool>>,
    /// `AclTreeNodes` representing ACL paths directly below the current one.
    pub children: BTreeMap<String, AclTreeNode>,
}

impl AclTreeNode {
    /// Creates a new, empty AclTreeNode.
    pub fn new() -> Self {
        Self {
            users: HashMap::new(),
            groups: HashMap::new(),
            children: BTreeMap::new(),
        }
    }

    /// Returns applicable [Role] and their propagation status for a given
    /// [Authid](crate::api2::types::Authid).
    ///
    /// If the `Authid` is a [User](crate::config::user::User) that has no specific `Roles` configured on this node,
    /// applicable `Group` roles will be returned instead.
    ///
    /// If `leaf` is `false`, only those roles where the propagate flag in the ACL is set to `true`
    /// are returned. Otherwise, all roles will be returned.
    pub fn extract_roles(&self, auth_id: &Authid, leaf: bool) -> HashMap<String, bool> {
        let user_roles = self.extract_user_roles(auth_id, leaf);
        if !user_roles.is_empty() || auth_id.is_token() {
            // user privs always override group privs
            return user_roles;
        };

        self.extract_group_roles(auth_id.user(), leaf)
    }

    fn extract_user_roles(&self, auth_id: &Authid, leaf: bool) -> HashMap<String, bool> {
        let mut map = HashMap::new();

        let roles = match self.users.get(auth_id) {
            Some(m) => m,
            None => return map,
        };

        for (role, propagate) in roles {
            if *propagate || leaf {
                if role == ROLE_NAME_NO_ACCESS {
                    // return a map with a single role 'NoAccess'
                    let mut map = HashMap::new();
                    map.insert(role.to_string(), false);
                    return map;
                }
                map.insert(role.to_string(), *propagate);
            }
        }

        map
    }

    fn extract_group_roles(&self, _user: &Userid, leaf: bool) -> HashMap<String, bool> {
        let mut map = HashMap::new();

        for (_group, roles) in &self.groups {
            let is_member = false; // fixme: check if user is member of the group
            if !is_member {
                continue;
            }

            for (role, propagate) in roles {
                if *propagate || leaf {
                    if role == ROLE_NAME_NO_ACCESS {
                        // return a map with a single role 'NoAccess'
                        let mut map = HashMap::new();
                        map.insert(role.to_string(), false);
                        return map;
                    }
                    map.insert(role.to_string(), *propagate);
                }
            }
        }

        map
    }

    fn delete_group_role(&mut self, group: &str, role: &str) {
        let roles = match self.groups.get_mut(group) {
            Some(r) => r,
            None => return,
        };
        roles.remove(role);
    }

    fn delete_user_role(&mut self, auth_id: &Authid, role: &str) {
        let roles = match self.users.get_mut(auth_id) {
            Some(r) => r,
            None => return,
        };
        roles.remove(role);
    }

    fn insert_group_role(&mut self, group: String, role: String, propagate: bool) {
        let map = self.groups.entry(group).or_insert_with(|| HashMap::new());
        if role == ROLE_NAME_NO_ACCESS {
            map.clear();
            map.insert(role, propagate);
        } else {
            map.remove(ROLE_NAME_NO_ACCESS);
            map.insert(role, propagate);
        }
    }

    fn insert_user_role(&mut self, auth_id: Authid, role: String, propagate: bool) {
        let map = self.users.entry(auth_id).or_insert_with(|| HashMap::new());
        if role == ROLE_NAME_NO_ACCESS {
            map.clear();
            map.insert(role, propagate);
        } else {
            map.remove(ROLE_NAME_NO_ACCESS);
            map.insert(role, propagate);
        }
    }
}

impl AclTree {
    /// Create a new, empty ACL tree with a single, empty root [node](AclTreeNode)
    pub fn new() -> Self {
        Self {
            root: AclTreeNode::new(),
        }
    }

    /// Iterates over the tree looking for a node matching `path`.
    pub fn find_node(&mut self, path: &str) -> Option<&mut AclTreeNode> {
        let path = split_acl_path(path);
        return self.get_node(&path);
    }

    fn get_node(&mut self, path: &[&str]) -> Option<&mut AclTreeNode> {
        let mut node = &mut self.root;
        for comp in path {
            node = match node.children.get_mut(*comp) {
                Some(n) => n,
                None => return None,
            };
        }
        Some(node)
    }

    fn get_or_insert_node(&mut self, path: &[&str]) -> &mut AclTreeNode {
        let mut node = &mut self.root;
        for comp in path {
            node = node
                .children
                .entry(String::from(*comp))
                .or_insert_with(|| AclTreeNode::new());
        }
        node
    }

    /// Deletes the specified `role` from the `group`'s ACL on `path`.
    ///
    /// Never fails, even if the `path` has no ACLs configured, or the `group`/`role` combination
    /// does not exist on `path`.
    pub fn delete_group_role(&mut self, path: &str, group: &str, role: &str) {
        let path = split_acl_path(path);
        let node = match self.get_node(&path) {
            Some(n) => n,
            None => return,
        };
        node.delete_group_role(group, role);
    }

    /// Deletes the specified `role` from the `user`'s ACL on `path`.
    ///
    /// Never fails, even if the `path` has no ACLs configured, or the `user`/`role` combination
    /// does not exist on `path`.
    pub fn delete_user_role(&mut self, path: &str, auth_id: &Authid, role: &str) {
        let path = split_acl_path(path);
        let node = match self.get_node(&path) {
            Some(n) => n,
            None => return,
        };
        node.delete_user_role(auth_id, role);
    }

    /// Inserts the specified `role` into the `group` ACL on `path`.
    ///
    /// The [AclTreeNode] representing `path` will be created and inserted into the tree if
    /// necessary.
    pub fn insert_group_role(&mut self, path: &str, group: &str, role: &str, propagate: bool) {
        let path = split_acl_path(path);
        let node = self.get_or_insert_node(&path);
        node.insert_group_role(group.to_string(), role.to_string(), propagate);
    }

    /// Inserts the specified `role` into the `user` ACL on `path`.
    ///
    /// The [AclTreeNode] representing `path` will be created and inserted into the tree if
    /// necessary.
    pub fn insert_user_role(&mut self, path: &str, auth_id: &Authid, role: &str, propagate: bool) {
        let path = split_acl_path(path);
        let node = self.get_or_insert_node(&path);
        node.insert_user_role(auth_id.to_owned(), role.to_string(), propagate);
    }

    fn write_node_config(node: &AclTreeNode, path: &str, w: &mut dyn Write) -> Result<(), Error> {
        let mut role_ug_map0 = HashMap::new();
        let mut role_ug_map1 = HashMap::new();

        for (auth_id, roles) in &node.users {
            // no need to save, because root is always 'Administrator'
            if !auth_id.is_token() && auth_id.user() == "root@pam" {
                continue;
            }
            for (role, propagate) in roles {
                let role = role.as_str();
                let auth_id = auth_id.to_string();
                if *propagate {
                    role_ug_map1
                        .entry(role)
                        .or_insert_with(|| BTreeSet::new())
                        .insert(auth_id);
                } else {
                    role_ug_map0
                        .entry(role)
                        .or_insert_with(|| BTreeSet::new())
                        .insert(auth_id);
                }
            }
        }

        for (group, roles) in &node.groups {
            for (role, propagate) in roles {
                let group = format!("@{}", group);
                if *propagate {
                    role_ug_map1
                        .entry(role)
                        .or_insert_with(|| BTreeSet::new())
                        .insert(group);
                } else {
                    role_ug_map0
                        .entry(role)
                        .or_insert_with(|| BTreeSet::new())
                        .insert(group);
                }
            }
        }

        fn group_by_property_list(
            item_property_map: &HashMap<&str, BTreeSet<String>>,
        ) -> BTreeMap<String, BTreeSet<String>> {
            let mut result_map = BTreeMap::new();
            for (item, property_map) in item_property_map {
                let item_list = property_map.iter().fold(String::new(), |mut acc, v| {
                    if !acc.is_empty() {
                        acc.push(',');
                    }
                    acc.push_str(v);
                    acc
                });
                result_map
                    .entry(item_list)
                    .or_insert_with(|| BTreeSet::new())
                    .insert(item.to_string());
            }
            result_map
        }

        let uglist_role_map0 = group_by_property_list(&role_ug_map0);
        let uglist_role_map1 = group_by_property_list(&role_ug_map1);

        fn role_list(roles: &BTreeSet<String>) -> String {
            if roles.contains(ROLE_NAME_NO_ACCESS) {
                return String::from(ROLE_NAME_NO_ACCESS);
            }
            roles.iter().fold(String::new(), |mut acc, v| {
                if !acc.is_empty() {
                    acc.push(',');
                }
                acc.push_str(v);
                acc
            })
        }

        for (uglist, roles) in &uglist_role_map0 {
            let role_list = role_list(roles);
            writeln!(
                w,
                "acl:0:{}:{}:{}",
                if path.is_empty() { "/" } else { path },
                uglist,
                role_list
            )?;
        }

        for (uglist, roles) in &uglist_role_map1 {
            let role_list = role_list(roles);
            writeln!(
                w,
                "acl:1:{}:{}:{}",
                if path.is_empty() { "/" } else { path },
                uglist,
                role_list
            )?;
        }

        for (name, child) in node.children.iter() {
            let child_path = format!("{}/{}", path, name);
            Self::write_node_config(child, &child_path, w)?;
        }

        Ok(())
    }

    fn write_config(&self, w: &mut dyn Write) -> Result<(), Error> {
        Self::write_node_config(&self.root, "", w)
    }

    fn parse_acl_line(&mut self, line: &str) -> Result<(), Error> {
        let items: Vec<&str> = line.split(':').collect();

        if items.len() != 5 {
            bail!("wrong number of items.");
        }

        if items[0] != "acl" {
            bail!("line does not start with 'acl'.");
        }

        let propagate = if items[1] == "0" {
            false
        } else if items[1] == "1" {
            true
        } else {
            bail!("expected '0' or '1' for propagate flag.");
        };

        let path_str = items[2];
        let path = split_acl_path(path_str);
        let node = self.get_or_insert_node(&path);

        let uglist: Vec<&str> = items[3].split(',').map(|v| v.trim()).collect();

        let rolelist: Vec<&str> = items[4].split(',').map(|v| v.trim()).collect();

        for user_or_group in &uglist {
            for role in &rolelist {
                if !ROLE_NAMES.contains_key(role) {
                    bail!("unknown role '{}'", role);
                }
                if user_or_group.starts_with('@') {
                    let group = &user_or_group[1..];
                    node.insert_group_role(group.to_string(), role.to_string(), propagate);
                } else {
                    node.insert_user_role(user_or_group.parse()?, role.to_string(), propagate);
                }
            }
        }

        Ok(())
    }

    fn load(filename: &Path) -> Result<(Self, [u8; 32]), Error> {
        let mut tree = Self::new();

        let raw = match std::fs::read_to_string(filename) {
            Ok(v) => v,
            Err(err) => {
                if err.kind() == std::io::ErrorKind::NotFound {
                    String::new()
                } else {
                    bail!("unable to read acl config {:?} - {}", filename, err);
                }
            }
        };

        let digest = openssl::sha::sha256(raw.as_bytes());

        for (linenr, line) in raw.lines().enumerate() {
            let line = line.trim();
            if line.is_empty() {
                continue;
            }
            if let Err(err) = tree.parse_acl_line(line) {
                bail!(
                    "unable to parse acl config {:?}, line {} - {}",
                    filename,
                    linenr + 1,
                    err
                );
            }
        }

        Ok((tree, digest))
    }

    #[cfg(test)]
    pub(crate) fn from_raw(raw: &str) -> Result<Self, Error> {
        let mut tree = Self::new();
        for (linenr, line) in raw.lines().enumerate() {
            let line = line.trim();
            if line.is_empty() {
                continue;
            }
            if let Err(err) = tree.parse_acl_line(line) {
                bail!(
                    "unable to parse acl config data, line {} - {}",
                    linenr + 1,
                    err
                );
            }
        }
        Ok(tree)
    }

    /// Returns a map of role name and propagation status for a given `auth_id` and `path`.
    ///
    /// This will collect role mappings according to the following algorithm:
    /// - iterate over all intermediate nodes along `path` and collect roles with `propagate` set
    /// - get all (propagating and non-propagating) roles for last component of path
    /// - more specific role maps replace less specific role maps
    /// -- user/token is more specific than group at each level
    /// -- roles lower in the tree are more specific than those higher up along the path
    pub fn roles(&self, auth_id: &Authid, path: &[&str]) -> HashMap<String, bool> {
        let mut node = &self.root;
        let mut role_map = node.extract_roles(auth_id, path.is_empty());

        for (pos, comp) in path.iter().enumerate() {
            let last_comp = (pos + 1) == path.len();
            node = match node.children.get(*comp) {
                Some(n) => n,
                None => return role_map, // path not found
            };

            let new_map = node.extract_roles(auth_id, last_comp);
            if !new_map.is_empty() {
                // overwrite previous maptings
                role_map = new_map;
            }
        }

        role_map
    }
}

/// Filename where [AclTree] is stored.
pub const ACL_CFG_FILENAME: &str = "/etc/proxmox-backup/acl.cfg";
/// Path used to lock the [AclTree] when modifying.
pub const ACL_CFG_LOCKFILE: &str = "/etc/proxmox-backup/.acl.lck";

/// Reads the [AclTree] from the [default path](ACL_CFG_FILENAME).
pub fn config() -> Result<(AclTree, [u8; 32]), Error> {
    let path = PathBuf::from(ACL_CFG_FILENAME);
    AclTree::load(&path)
}

/// Returns a cached [AclTree] or fresh copy read directly from the [default path](ACL_CFG_FILENAME)
///
/// Since the AclTree is used for every API request's permission check, this caching mechanism
/// allows to skip reading and parsing the file again if it is unchanged.
pub fn cached_config() -> Result<Arc<AclTree>, Error> {
    struct ConfigCache {
        data: Option<Arc<AclTree>>,
        last_mtime: i64,
        last_mtime_nsec: i64,
    }

    lazy_static! {
        static ref CACHED_CONFIG: RwLock<ConfigCache> = RwLock::new(ConfigCache {
            data: None,
            last_mtime: 0,
            last_mtime_nsec: 0
        });
    }

    let stat = match nix::sys::stat::stat(ACL_CFG_FILENAME) {
        Ok(stat) => Some(stat),
        Err(nix::Error::Sys(nix::errno::Errno::ENOENT)) => None,
        Err(err) => bail!("unable to stat '{}' - {}", ACL_CFG_FILENAME, err),
    };

    {
        // limit scope
        let cache = CACHED_CONFIG.read().unwrap();
        if let Some(ref config) = cache.data {
            if let Some(stat) = stat {
                if stat.st_mtime == cache.last_mtime && stat.st_mtime_nsec == cache.last_mtime_nsec
                {
                    return Ok(config.clone());
                }
            } else if cache.last_mtime == 0 && cache.last_mtime_nsec == 0 {
                return Ok(config.clone());
            }
        }
    }

    let (config, _digest) = config()?;
    let config = Arc::new(config);

    let mut cache = CACHED_CONFIG.write().unwrap();
    if let Some(stat) = stat {
        cache.last_mtime = stat.st_mtime;
        cache.last_mtime_nsec = stat.st_mtime_nsec;
    }
    cache.data = Some(config.clone());

    Ok(config)
}

/// Saves an [AclTree] to the [default path](ACL_CFG_FILENAME), ensuring proper ownership and
/// file permissions.
pub fn save_config(acl: &AclTree) -> Result<(), Error> {
    let mut raw: Vec<u8> = Vec::new();

    acl.write_config(&mut raw)?;

    let backup_user = crate::backup::backup_user()?;
    let mode = nix::sys::stat::Mode::from_bits_truncate(0o0640);
    // set the correct owner/group/permissions while saving file
    // owner(rw) = root, group(r)= backup
    let options = CreateOptions::new()
        .perm(mode)
        .owner(nix::unistd::ROOT)
        .group(backup_user.gid);

    replace_file(ACL_CFG_FILENAME, &raw, options)?;

    Ok(())
}

#[cfg(test)]
mod test {
    use super::AclTree;
    use anyhow::Error;

    use crate::api2::types::Authid;

    fn check_roles(tree: &AclTree, auth_id: &Authid, path: &str, expected_roles: &str) {
        let path_vec = super::split_acl_path(path);
        let mut roles = tree
            .roles(auth_id, &path_vec)
            .iter()
            .map(|(v, _)| v.clone())
            .collect::<Vec<String>>();
        roles.sort();
        let roles = roles.join(",");

        assert_eq!(
            roles, expected_roles,
            "\nat check_roles for '{}' on '{}'",
            auth_id, path
        );
    }

    #[test]
    fn test_acl_line_compression() {
        let tree = AclTree::from_raw(
            "\
            acl:0:/store/store2:user1@pbs:Admin\n\
            acl:0:/store/store2:user2@pbs:Admin\n\
            acl:0:/store/store2:user1@pbs:DatastoreBackup\n\
            acl:0:/store/store2:user2@pbs:DatastoreBackup\n\
            ",
        )
        .expect("failed to parse acl tree");

        let mut raw: Vec<u8> = Vec::new();
        tree.write_config(&mut raw)
            .expect("failed to write acl tree");
        let raw = std::str::from_utf8(&raw).expect("acl tree is not valid utf8");

        assert_eq!(
            raw,
            "acl:0:/store/store2:user1@pbs,user2@pbs:Admin,DatastoreBackup\n"
        );
    }

    #[test]
    fn test_roles_1() -> Result<(), Error> {
        let tree = AclTree::from_raw(
            r###"
acl:1:/storage:user1@pbs:Admin
acl:1:/storage/store1:user1@pbs:DatastoreBackup
acl:1:/storage/store2:user2@pbs:DatastoreBackup
"###,
        )?;
        let user1: Authid = "user1@pbs".parse()?;
        check_roles(&tree, &user1, "/", "");
        check_roles(&tree, &user1, "/storage", "Admin");
        check_roles(&tree, &user1, "/storage/store1", "DatastoreBackup");
        check_roles(&tree, &user1, "/storage/store2", "Admin");

        let user2: Authid = "user2@pbs".parse()?;
        check_roles(&tree, &user2, "/", "");
        check_roles(&tree, &user2, "/storage", "");
        check_roles(&tree, &user2, "/storage/store1", "");
        check_roles(&tree, &user2, "/storage/store2", "DatastoreBackup");

        Ok(())
    }

    #[test]
    fn test_role_no_access() -> Result<(), Error> {
        let tree = AclTree::from_raw(
            r###"
acl:1:/:user1@pbs:Admin
acl:1:/storage:user1@pbs:NoAccess
acl:1:/storage/store1:user1@pbs:DatastoreBackup
"###,
        )?;
        let user1: Authid = "user1@pbs".parse()?;
        check_roles(&tree, &user1, "/", "Admin");
        check_roles(&tree, &user1, "/storage", "NoAccess");
        check_roles(&tree, &user1, "/storage/store1", "DatastoreBackup");
        check_roles(&tree, &user1, "/storage/store2", "NoAccess");
        check_roles(&tree, &user1, "/system", "Admin");

        let tree = AclTree::from_raw(
            r###"
acl:1:/:user1@pbs:Admin
acl:0:/storage:user1@pbs:NoAccess
acl:1:/storage/store1:user1@pbs:DatastoreBackup
"###,
        )?;
        check_roles(&tree, &user1, "/", "Admin");
        check_roles(&tree, &user1, "/storage", "NoAccess");
        check_roles(&tree, &user1, "/storage/store1", "DatastoreBackup");
        check_roles(&tree, &user1, "/storage/store2", "Admin");
        check_roles(&tree, &user1, "/system", "Admin");

        Ok(())
    }

    #[test]
    fn test_role_add_delete() -> Result<(), Error> {
        let mut tree = AclTree::new();

        let user1: Authid = "user1@pbs".parse()?;

        tree.insert_user_role("/", &user1, "Admin", true);
        tree.insert_user_role("/", &user1, "Audit", true);

        check_roles(&tree, &user1, "/", "Admin,Audit");

        tree.insert_user_role("/", &user1, "NoAccess", true);
        check_roles(&tree, &user1, "/", "NoAccess");

        let mut raw: Vec<u8> = Vec::new();
        tree.write_config(&mut raw)?;
        let raw = std::str::from_utf8(&raw)?;

        assert_eq!(raw, "acl:1:/:user1@pbs:NoAccess\n");

        Ok(())
    }

    #[test]
    fn test_no_access_overwrite() -> Result<(), Error> {
        let mut tree = AclTree::new();

        let user1: Authid = "user1@pbs".parse()?;

        tree.insert_user_role("/storage", &user1, "NoAccess", true);

        check_roles(&tree, &user1, "/storage", "NoAccess");

        tree.insert_user_role("/storage", &user1, "Admin", true);
        tree.insert_user_role("/storage", &user1, "Audit", true);

        check_roles(&tree, &user1, "/storage", "Admin,Audit");

        tree.insert_user_role("/storage", &user1, "NoAccess", true);

        check_roles(&tree, &user1, "/storage", "NoAccess");

        Ok(())
    }
}