use serde::Deserialize;

#[derive(Debug, Deserialize)]
pub struct Config {
    pub uplink: Uplink,
    pub server: Server,
    // Node-to-node replication. Absent = single node, no gossip.
    #[serde(default)]
    pub gossip: Option<Gossip>,
    #[serde(default)]
    pub peer: Vec<Peer>,
    // Outbound email (password resets). Absent = email features are off.
    #[serde(default)]
    pub email: Option<Email>,
    // Directory replication (gRPC), for websites mirroring the account/channel
    // directory. Absent = the RPC server does not start.
    #[serde(default)]
    pub grpc: Option<Grpc>,
    // JSON-RPC stats endpoint (plain HTTP+JSON) for a website's stats pages.
    // Absent = it does not start. Bind to localhost; a token is required.
    #[serde(default)]
    pub jsonrpc: Option<JsonRpc>,
    // Which service modules to start. Absent = the full standard suite (all the
    // pseudo-clients); listing it trims that set. Every service is first-class.
    #[serde(default)]
    pub modules: Modules,
    // Services operators: accounts granted privileges. Absent = no opers.
    #[serde(default)]
    pub oper: Vec<Oper>,
    // Staff audit feed. Absent = no audit log is emitted.
    #[serde(default)]
    pub log: Option<Log>,
    // Inactivity-expiry. Absent = accounts and channels never expire.
    #[serde(default)]
    pub expire: Option<Expire>,
    // Per-IP session limiting. Absent = unlimited.
    #[serde(default)]
    pub session: Option<Session>,
    // Account authority. Absent = built-in (echo owns accounts). With
    // `external = true`, an outside authority (e.g. the website) owns identity
    // and pushes accounts in; IRC can only authenticate.
    #[serde(default)]
    pub auth: Option<Auth>,
    // Website single-use keycards (passwordless web login). Absent = keycard
    // credentials (`kc_…` over SASL) are not honoured.
    #[serde(default)]
    pub keycard: Option<Keycard>,
    // DictServ dictionary lookups (dict.org / RFC 2229). Absent = the service does
    // not load and echo makes no outbound lookup requests. Opt-in on purpose.
    #[serde(default)]
    pub dictserv: Option<Dict>,
    // Registration policy. Absent = defaults (the look-alike guard is on).
    #[serde(default)]
    pub register: Register,
    // Which InspIRCd matching-extbans AKICK may use. Absent = every extban echo
    // knows (full compatibility). List `enabled` to restrict it — e.g. drop the
    // ones your ircd doesn't provide.
    #[serde(default)]
    pub extban: Option<Extban>,
}

#[derive(Debug, Deserialize, Clone)]
pub struct Extban {
    // Enabled extban names ("account", "realname", "country", …). Empty = all.
    #[serde(default)]
    pub enabled: Vec<String>,
}

// Redeeming a website login keycard: a member already authenticated on the
// website connects with a one-time `kc_…` token instead of their password. We
// hand it to Django's localhost login-token endpoint, which redeems it and
// confirms the account. `url` is that endpoint; `api_key` matches its X-API-Key.
#[derive(Debug, Deserialize, Clone)]
pub struct Keycard {
    pub url: String,
    pub api_key: String,
}

// DictServ. `server` is a DICT-protocol endpoint (RFC 2229); dict.org hosts the
// standard databases (WordNet, GCIDE, thesaurus, …).
#[derive(Debug, Deserialize, Clone)]
pub struct Dict {
    #[serde(default = "default_dict_server")]
    pub server: String,
}

fn default_dict_server() -> String {
    "dict.org:2628".to_string()
}

// Registration policy.
#[derive(Debug, Deserialize, Clone)]
#[serde(default)]
pub struct Register {
    // Reject look-alike / mixed-script / invisible registration names. On by
    // default; turn it off for a community that legitimately uses mixed or
    // non-Latin names. Reloadable with REHASH.
    pub confusable_check: bool,
}

impl Default for Register {
    fn default() -> Self {
        Self { confusable_check: true }
    }
}

// Account-authority configuration.
#[derive(Debug, Deserialize, Clone)]
pub struct Auth {
    #[serde(default)]
    pub external: bool,
}

// Session limiting: the default connections allowed per IP (0/absent = off),
// which OperServ EXCEPTION entries can raise or lower per IP-mask.
#[derive(Debug, Deserialize, Clone)]
pub struct Session {
    #[serde(default)]
    pub default_limit: u32,
}

impl Session {
    pub fn limit(&self) -> Option<u32> {
        (self.default_limit > 0).then_some(self.default_limit)
    }
}

// Inactivity-expiry thresholds, in days. A zero (or omitted) field leaves that
// kind never expiring, so an operator can expire only accounts, only channels,
// or both.
#[derive(Debug, Deserialize, Clone)]
pub struct Expire {
    #[serde(default)]
    pub accounts_days: u64,
    #[serde(default)]
    pub channels_days: u64,
    // Days before expiry to email a warning to the owner (0 = no warning email).
    #[serde(default)]
    pub warn_days: u64,
}

impl Expire {
    // The thresholds in seconds, or None where that kind is disabled (zero days).
    pub fn account_ttl(&self) -> Option<u64> {
        (self.accounts_days > 0).then(|| self.accounts_days * 86_400)
    }
    pub fn channel_ttl(&self) -> Option<u64> {
        (self.channels_days > 0).then(|| self.channels_days * 86_400)
    }
    // The warning lead time in seconds, or None if warnings are off.
    pub fn warn_ttl(&self) -> Option<u64> {
        (self.warn_days > 0).then(|| self.warn_days * 86_400)
    }
}

// The staff audit feed: notable service actions are announced to this channel
// so operators can see who did what.
#[derive(Debug, Deserialize, Clone)]
pub struct Log {
    pub channel: String,
    // Masks NOTIFY never announces, three kinds: `#channel` mutes that channel,
    // `server:<glob>` (or `via:`) mutes everyone on a matching server — the handle
    // on a relay whose users have clean nicks — and any other mask (nick glob /
    // user@host / extban) mutes a user. E.g. "*/*" silences PyLink relays that
    // suffix nicks, "server:chatnova.relay" a relay that doesn't, "#staff" keeps a
    // broad `#*` watch out of a channel. Reloadable with REHASH.
    #[serde(default)]
    pub notify_exclude: Vec<String>,
}

// One services operator: an account and the privileges it holds.
#[derive(Debug, Deserialize, Clone)]
pub struct Oper {
    pub account: String,
    #[serde(default)]
    pub privs: Vec<String>, // fine-grained: auspex, oper, suspend, admin, root
    // A tier shortcut: "operator", "administrator", or "root" — expands to the
    // matching privilege (which implies the lower tiers). Combined with `privs`.
    #[serde(default, rename = "type")]
    pub oper_type: Option<String>,
}

impl Oper {
    // Every privilege-name granted, from both the `type` shortcut and the explicit
    // `privs` list.
    fn all_priv_names(&self) -> Vec<String> {
        let mut names = self.privs.clone();
        if let Some(t) = &self.oper_type {
            names.push(t.clone());
        }
        names
    }
}

impl Config {
    // The account -> privileges table (casefolded keys) built from [[oper]].
    pub fn opers(&self) -> std::collections::HashMap<String, echo_api::Privs> {
        let mut map = std::collections::HashMap::new();
        for o in &self.oper {
            map.insert(o.account.to_ascii_lowercase(), echo_api::Privs::from_names(&o.all_priv_names()));
        }
        map
    }

    // (account, unrecognised-privilege-name) pairs across all [[oper]] blocks, so
    // the caller can warn about a typo that would otherwise silently grant nothing.
    pub fn oper_priv_warnings(&self) -> Vec<(String, String)> {
        self.oper
            .iter()
            .flat_map(|o| {
                let (_, unknown) = echo_api::Privs::parse_names(&o.all_priv_names());
                unknown.into_iter().map(move |name| (o.account.clone(), name))
            })
            .collect()
    }
}

// The service modules to bring up at burst. Each name maps to a compiled-in
// module crate the daemon knows how to construct (see main.rs). Names not built
// in are ignored.
#[derive(Debug, Deserialize)]
pub struct Modules {
    #[serde(default = "default_services")]
    pub services: Vec<String>,
}

impl Default for Modules {
    fn default() -> Self {
        Modules { services: default_services() }
    }
}

// The full standard suite: every pseudo-client is a first-class service and
// comes up by default. An admin trims the list; there is no second tier.
fn default_services() -> Vec<String> {
    [
        "nickserv", "chanserv", "botserv", "hostserv", "memoserv", "operserv", "statserv",
        "groupserv", "infoserv", "reportserv", "helpserv", "chanfix", "diceserv", "gameserv", "debugserv",
    ]
    .iter()
    .map(|s| s.to_string())
    .collect()
}

#[derive(Debug, Deserialize, Clone)]
pub struct Grpc {
    // Address to accept client connections on, e.g. "127.0.0.1:50051".
    pub bind: String,
    // Bearer token every RPC must present (`authorization: Bearer <token>`).
    pub token: String,
    // Optional server-side TLS (no client cert required, unlike gossip's mTLS —
    // a subscriber is a website backend, not a federation peer).
    #[serde(default)]
    pub tls: Option<ServerTls>,
}

#[derive(Debug, Deserialize, Clone)]
pub struct ServerTls {
    pub cert: String, // certificate chain (PEM)
    pub key: String,  // private key (PEM)
}

#[derive(Debug, Deserialize, Clone)]
pub struct JsonRpc {
    // Address to accept HTTP on, e.g. "127.0.0.1:5601". Keep it on localhost and
    // let a reverse proxy terminate TLS / HTTP-2 / HTTP-3.
    pub bind: String,
    // Bearer token every request must present (`authorization: Bearer <token>`).
    pub token: String,
    // Browser origins allowed to call this cross-site (CORS), e.g.
    // ["https://tchatou.fr", "https://swaygo.fr"]. Empty = no browser access.
    #[serde(default)]
    pub origins: Vec<String>,
    // Terminate TLS here (enabling HTTP/2). Absent = plain HTTP, for when a
    // reverse proxy does TLS. Reuses the same cert/key shape as [grpc].
    #[serde(default)]
    pub tls: Option<ServerTls>,
}

#[derive(Debug, Deserialize, Clone)]
pub struct Email {
    // Sender address stamped on outgoing mail.
    pub from: String,
    // A shell command the message is piped to on stdin, e.g. "sendmail -t" or
    // "msmtp -t". Run via `sh -c`, so redirection and pipes work.
    pub command: String,
    // Display name shown in email templates (header/footer).
    #[serde(default = "default_brand")]
    pub brand: String,
    // Accent colour (any CSS colour) for the email template.
    #[serde(default = "default_accent")]
    pub accent: String,
    // Optional logo image URL shown in the email header (must be a hosted image;
    // email clients don't render inline SVG or data URIs).
    #[serde(default)]
    pub logo: String,
}

fn default_brand() -> String {
    "Network Services".to_string()
}

fn default_accent() -> String {
    "#4f46e5".to_string()
}

#[derive(Debug, Deserialize, Clone)]
pub struct Gossip {
    // Address to accept peer connections on. Absent = dial-only node.
    pub bind: Option<String>,
    // Shared secret both nodes must present.
    pub secret: String,
    // Mutual-TLS for the peer link. Absent = plaintext.
    #[serde(default)]
    pub tls: Option<Tls>,
}

#[derive(Debug, Deserialize, Clone)]
pub struct Tls {
    pub cert: String, // our certificate chain (PEM)
    pub key: String,  // our private key (PEM)
    pub ca: String,   // CA bundle that must have signed a peer's certificate (PEM)
}

#[derive(Debug, Deserialize, Clone)]
pub struct Peer {
    pub addr: String,
    // TLS server name to expect from this peer; must match its certificate.
    #[serde(default = "default_peer_name")]
    pub name: String,
}

fn default_peer_name() -> String {
    "echo".to_string()
}

#[derive(Debug, Deserialize)]
pub struct Uplink {
    pub host: String,
    pub port: u16,
    pub password: String,
}

#[derive(Debug, Deserialize)]
pub struct Server {
    pub name: String,
    pub sid: String,
    pub description: String,
    #[serde(default = "default_protocol")]
    pub protocol: u32,
    // PBKDF2 cost baked into new SCRAM verifiers at registration. High by
    // default for offline-attack resistance; lower it if registration latency
    // on the single-threaded link matters more than verifier strength.
    #[serde(default = "default_scram_iterations")]
    pub scram_iterations: u32,
    // Nick prefix a user is renamed to on NickServ LOGOUT (they keep the ircd's
    // guest number appended, e.g. Guest12345). Must start with a letter — the
    // ircd rejects a digit-leading SVSNICK and falls back to the raw uuid.
    #[serde(default = "default_guest_nick")]
    pub guest_nick: String,
    // Hostname the service pseudo-clients wear (NickServ!services@<here>). Empty
    // falls back to the server name, so NickServ shows as ...@services.tchatou.fr
    // rather than the generic default.
    #[serde(default)]
    pub service_host: String,
    // User modes the service pseudo-clients (services + bots) are introduced with.
    // Default "iHkBT": invisible, hideoper, servprotect (unkillable — needs the
    // services server U-lined), bot, block-CTCP. Set per the ircd's loaded modules.
    #[serde(default = "default_service_modes")]
    pub service_modes: String,
    // Oper type the service pseudo-clients are flagged with, so WHOIS shows
    // "is a <this>". Default "Network Service". Empty leaves them non-opers.
    #[serde(default = "default_service_oper_type")]
    pub service_oper_type: String,
    // Channel every service pseudo-client (NickServ, ChanServ, …) joins at
    // startup. Default "#services"; empty leaves them out of any channel.
    #[serde(default = "default_services_channel")]
    pub services_channel: String,
    // Emit IRCv3 standard replies (FAIL/WARN/NOTE) for service errors instead of
    // plain notices. Needs m_services_stdrpl loaded on the ircd; off until then,
    // otherwise the replies are dropped. Off = today's notice behaviour.
    #[serde(default)]
    pub standard_replies: bool,
}

fn default_services_channel() -> String {
    "#services".to_string()
}

fn default_service_modes() -> String {
    "ikBT".to_string()
}

fn default_service_oper_type() -> String {
    "Network Service".to_string()
}

fn default_protocol() -> u32 {
    1206 // InspIRCd 4 spanning-tree protocol (1205 = insp3)
}

fn default_guest_nick() -> String {
    "Guest".to_string()
}

fn default_scram_iterations() -> u32 {
    crate::engine::scram::DEFAULT_ITERATIONS
}

impl Config {
    pub fn load(path: &str) -> anyhow::Result<Self> {
        let raw = std::fs::read_to_string(path)?;
        let cfg: Config = toml::from_str(&raw)?;
        cfg.validate()?;
        Ok(cfg)
    }

    // Catch the common misconfigurations up front with a clear message, rather
    // than failing cryptically at link time.
    fn validate(&self) -> anyhow::Result<()> {
        let sid = &self.server.sid;
        if sid.len() != 3 || !sid.chars().all(|c| c.is_ascii_alphanumeric()) {
            anyhow::bail!("server.sid must be exactly 3 alphanumeric characters (got {sid:?})");
        }
        if self.server.name.trim().is_empty() {
            anyhow::bail!("server.name must not be empty");
        }
        if self.uplink.host.trim().is_empty() {
            anyhow::bail!("uplink.host must not be empty");
        }
        Ok(())
    }
}