//! Crate-wide error type.

use proton_sdk::api::HumanVerification;
use thiserror::Error;

use crate::control::ErrorKind;

#[derive(Debug, Error)]
pub enum Error {
    #[error("proton api: {0}")]
    Proton(#[from] proton_sdk::ProtonError),

    #[error("keyring: {0}")]
    Keyring(#[from] keyring_core::Error),

    #[error("serialization: {0}")]
    Serde(#[from] serde_json::Error),

    #[error("io: {0}")]
    Io(#[from] std::io::Error),

    #[error("database: {0}")]
    Db(#[from] rusqlite::Error),

    /// No persisted session found — caller must run an interactive login.
    #[error("not logged in (no saved session)")]
    NotLoggedIn,

    /// The stored session can no longer unlock the account key chain: reading
    /// the key salts needs the `locked` scope, which a refreshed access token
    /// does not have. Only a fresh password login restores it.
    #[error("saved session can no longer unlock your keys — run `pdfs login` again")]
    ReloginRequired,

    /// The account has a separate mailbox password that has not been entered
    /// since login, so its keys cannot be unlocked. The fix is
    /// [`auth::unlock`](crate::auth::unlock), not a new login.
    #[error("account is locked — enter the mailbox password with `pdfs unlock`")]
    Locked,

    /// The mailbox password was checked against the account and is wrong.
    #[error("that mailbox password does not unlock your account")]
    WrongMailboxPassword,

    /// The login was gated behind human verification. Not a failure the user can
    /// fix by retrying: the challenge has to be solved and the login restarted
    /// with the resulting token (see [`auth::login_verified`](crate::auth::login_verified)).
    ///
    /// Carries the challenge rather than just a message so a front-end can
    /// present it; a front-end that cannot (no webview) still has prose to show.
    #[error("sign-in needs human verification — complete the CAPTCHA to continue")]
    HumanVerificationRequired(Box<HumanVerification>),

    #[error("{0}")]
    Other(String),
}

impl Error {
    /// Whether this is the local disk being full (`ENOSPC`), as opposed to any
    /// other I/O failure.
    ///
    /// Worth distinguishing because it is the one storage failure the user can
    /// act on, and because the caller's response differs: a full disk is met by
    /// evicting cached blobs and answering `ENOSPC`, where `EIO` would read as a
    /// broken file. `std::io::ErrorKind::StorageFull` is still unstable, so this
    /// compares the raw code.
    pub fn is_disk_full(&self) -> bool {
        match self {
            Error::Io(e) => e.raw_os_error() == Some(libc::ENOSPC),
            // SQLite reports it as its own code rather than surfacing the errno.
            Error::Db(rusqlite::Error::SqliteFailure(e, _)) => {
                e.code == rusqlite::ErrorCode::DiskFull
            }
            _ => false,
        }
    }
}

impl Error {
    /// Whether a control-socket round-trip gave up waiting for the reply: the
    /// daemon is running but stuck, as opposed to not running at all.
    pub fn is_timeout(&self) -> bool {
        matches!(
            self,
            Error::Io(e) if matches!(
                e.kind(),
                std::io::ErrorKind::WouldBlock | std::io::ErrorKind::TimedOut
            )
        )
    }
}

pub type Result<T> = std::result::Result<T, Error>;

/// A failure on its way to a front-end: prose for the user, plus the
/// [`ErrorKind`] the front-end actually branches on.
///
/// This is what the daemon's request-serving methods return, as opposed to
/// [`Error`] above, which is the plumbing error of the `pdfs-core` layer. The
/// two meet at the `From` impls below: a `rusqlite` or `io` failure carries no
/// information a user can act on, so it arrives here as
/// [`ErrorKind::Internal`] and keeps its text only for the log.
///
/// Classification happens where the failure is *understood* — at the API
/// boundary that knows a 404 from a 403, at the path resolver that knows an
/// `ENOENT` — never at the call site, which by then has only a string.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct CoreError {
    pub kind: ErrorKind,
    pub message: String,
}

impl CoreError {
    pub fn new(kind: ErrorKind, message: impl Into<String>) -> Self {
        Self {
            kind,
            message: message.into(),
        }
    }

    /// The API is unreachable. Carries fixed wording because there is only ever
    /// one thing to say about it.
    pub fn offline() -> Self {
        Self::new(ErrorKind::Offline, "the Proton Drive API is unreachable")
    }

    pub fn not_found(what: impl Into<String>) -> Self {
        Self::new(ErrorKind::NotFound, what)
    }

    pub fn denied(what: impl Into<String>) -> Self {
        Self::new(ErrorKind::Denied, what)
    }

    pub fn conflict(what: impl Into<String>) -> Self {
        Self::new(ErrorKind::Conflict, what)
    }

    pub fn invalid(what: impl Into<String>) -> Self {
        Self::new(ErrorKind::Invalid, what)
    }

    pub fn remote(what: impl Into<String>) -> Self {
        Self::new(ErrorKind::Remote, what)
    }

    pub fn internal(what: impl Into<String>) -> Self {
        Self::new(ErrorKind::Internal, what)
    }

    /// Classify a failure from an SDK call, prefixing `what` for the log.
    ///
    /// Takes `&dyn Error` rather than `&ProtonError` so it reads the same
    /// through the boxes the drain deals in, where the concrete type survives
    /// but the static one does not.
    ///
    /// A transport error, a timeout or a TLS failure is what being offline
    /// looks like from here, so it classifies as [`ErrorKind::Offline`] rather
    /// than [`ErrorKind::Remote`]: the request never reached Proton, and
    /// telling the user their connection is down beats telling them the
    /// server refused. The SDK's other failures say what went wrong instead
    /// (see [`proton_kind`]).
    ///
    /// Callers also hand it this crate's [`Error`] from the cache and the
    /// database, which is not a transport error at all. Taking those for
    /// "offline" told the user their connection was down when a pin failed on
    /// the database (`docs/BUGS.md` B266), so the source chain is searched for
    /// either type before falling back.
    pub fn from_api(e: &(dyn std::error::Error + 'static), what: &str) -> Self {
        Self::new(api_kind_of(e), format!("{what}: {e}"))
    }

    /// Prefix the message while keeping the classification.
    ///
    /// For adding the caller's context to an already-classified failure — the
    /// kind was decided by whoever understood the error and must survive being
    /// passed up.
    pub fn context(mut self, what: &str) -> Self {
        self.message = format!("{what}: {}", self.message);
        self
    }
}

impl std::fmt::Display for CoreError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.message)
    }
}

impl std::error::Error for CoreError {}

impl From<rusqlite::Error> for CoreError {
    fn from(e: rusqlite::Error) -> Self {
        Self::internal(format!("database: {e}"))
    }
}

impl From<std::io::Error> for CoreError {
    fn from(e: std::io::Error) -> Self {
        Self::internal(format!("io: {e}"))
    }
}

impl From<serde_json::Error> for CoreError {
    fn from(e: serde_json::Error) -> Self {
        Self::internal(format!("serialization: {e}"))
    }
}

impl From<Error> for CoreError {
    fn from(e: Error) -> Self {
        Self::new(core_kind(&e), e.to_string())
    }
}

/// What this crate's [`Error`] means to a front-end.
fn core_kind(e: &Error) -> ErrorKind {
    match e {
        Error::NotLoggedIn
        | Error::ReloginRequired
        | Error::Locked
        | Error::WrongMailboxPassword
        | Error::HumanVerificationRequired(_) => ErrorKind::Denied,
        Error::Proton(proton) => proton_kind(proton),
        _ => ErrorKind::Internal,
    }
}

/// The kind for [`CoreError::from_api`]: the first SDK or crate error in `e`'s
/// source chain decides it.
fn api_kind_of(e: &(dyn std::error::Error + 'static)) -> ErrorKind {
    let mut cause = Some(e);
    while let Some(err) = cause {
        if let Some(proton) = err.downcast_ref::<proton_sdk::ProtonError>() {
            return proton_kind(proton);
        }
        if let Some(core) = err.downcast_ref::<Error>() {
            return core_kind(core);
        }
        cause = err.source();
    }
    // Not the SDK's at all: a timeout around the call, or the socket.
    ErrorKind::Offline
}

/// What a failed SDK call means to a front-end.
///
/// Only a transport failure is the connection. The rest happened on this
/// machine, and calling them "offline" sent the user to check a network that
/// worked (issue #38: a photo upload on an account without a photo library
/// read "You're offline").
fn proton_kind(e: &proton_sdk::ProtonError) -> ErrorKind {
    use proton_sdk::ProtonError as P;
    match e {
        P::Api(api) => api_kind(api.code),
        P::Transport(_) => ErrorKind::Offline,
        // Proton answered, but not with anything this client can read.
        P::Serialization(_) => ErrorKind::Remote,
        // The SDK refused the call before sending it, such as an upload to a
        // photo library the account does not have.
        P::InvalidOperation(_) => ErrorKind::Invalid,
        P::Crypto(_) | P::KeysLocked => ErrorKind::Internal,
    }
}

/// What an API response code means to a front-end.
///
/// The grouping is by *what the user can do about it*, which is what
/// [`ErrorKind`] exists to express — not by HTTP-ish similarity. So a 403 and a
/// `NotEnoughPermissions` land together despite being different numbers, while
/// `AlreadyExists` and `DoesNotExist` stay apart despite both being 25xx.
fn api_kind(code: proton_sdk::api::ResponseCode) -> ErrorKind {
    use proton_sdk::api::ResponseCode as C;
    match code {
        // The account may not do this, and repeating it will not help.
        C::Unauthorized
        | C::Forbidden
        | C::NotEnoughPermissions
        | C::NotEnoughPermissionsToGrantPermissions
        | C::InsufficientScope
        | C::IncorrectLoginCredentials
        | C::InvalidRefreshToken
        | C::AccountDeleted
        | C::AccountDisabled
        | C::NoActiveSubscription => ErrorKind::Denied,

        C::DoesNotExist => ErrorKind::NotFound,

        // The remote moved underneath the request; the caller has to decide.
        C::AlreadyExists | C::IncompatibleState => ErrorKind::Conflict,

        // The request was malformed or asks for something structurally
        // impossible. A bug in the caller, not a condition to retry.
        C::InvalidRequirements
        | C::InvalidValue
        | C::InvalidEncryptedIdFormat
        | C::InvalidApp
        | C::TooManyChildren
        | C::NestingTooDeep => ErrorKind::Invalid,

        C::InsufficientQuota | C::InsufficientSpace | C::InsufficientVolumeQuota => {
            ErrorKind::Quota
        }

        // Reached Proton, but it could not answer *now*. Retrying is exactly
        // the right response, so these are Offline rather than Remote — the
        // front-end already words that as "not right now".
        C::RequestTimeout
        | C::Timeout
        | C::TooManyRequests
        | C::ServiceUnavailable
        | C::Offline => ErrorKind::Offline,

        // Reached Proton and it refused for a reason we have no specific
        // handling for. Retryable, because an unchanged retry can legitimately
        // succeed against a transient server-side condition.
        _ => ErrorKind::Remote,
    }
}

/// Whether `e` says the session itself is gone: its refresh token was refused,
/// or the account was deleted or disabled.
///
/// Nothing but a new login helps then, and no retry will ever succeed, so a
/// caller must not take it for a lost connection and wait for it to come back
/// (issue #35: a revoked session was shown as "offline" for good).
pub fn session_revoked(e: &proton_sdk::ProtonError) -> bool {
    use proton_sdk::api::ResponseCode as C;
    match e {
        proton_sdk::ProtonError::Api(api) => {
            api.is_invalid_refresh_token()
                || matches!(api.code, C::AccountDeleted | C::AccountDisabled)
        }
        _ => false,
    }
}

/// Whether `e` is Proton's temporary block on a sign-in (code 2028).
///
/// Its message says the app version is no longer supported, which is not what
/// happened: the release is current and only waiting helps (issues #28, #39).
/// A front-end must say that instead of passing the message through.
pub fn sign_in_blocked(e: &proton_sdk::ProtonError) -> bool {
    matches!(e, proton_sdk::ProtonError::Api(api) if api.code == proton_sdk::api::ResponseCode::Blocked)
}

/// The result every request-serving method in the daemon returns.
pub type CoreResult<T> = std::result::Result<T, CoreError>;

#[cfg(test)]
mod tests {
    use super::*;
    use proton_sdk::api::ResponseCode as C;
    use proton_sdk::{ProtonApiError, ProtonError};

    fn api(code: C) -> ProtonError {
        ProtonError::Api(ProtonApiError {
            code,
            http_status: 422,
            message: "nope".into(),
            details: None,
        })
    }

    #[test]
    fn api_codes_classify_by_what_the_user_can_do() {
        assert_eq!(api_kind(C::Forbidden), ErrorKind::Denied);
        assert_eq!(api_kind(C::NotEnoughPermissions), ErrorKind::Denied);
        assert_eq!(api_kind(C::DoesNotExist), ErrorKind::NotFound);
        assert_eq!(api_kind(C::AlreadyExists), ErrorKind::Conflict);
        assert_eq!(api_kind(C::InvalidValue), ErrorKind::Invalid);
        assert_eq!(api_kind(C::InsufficientSpace), ErrorKind::Quota);
        assert_eq!(api_kind(C::TooManyRequests), ErrorKind::Offline);
        // Nothing specific known about it, but Proton did answer.
        assert_eq!(api_kind(C::ProtonDriveUnknown), ErrorKind::Remote);
    }

    #[test]
    fn only_a_refused_refresh_or_a_closed_account_revokes_the_session() {
        assert!(session_revoked(&api(C::InvalidRefreshToken)));
        assert!(session_revoked(&api(C::AccountDeleted)));
        assert!(session_revoked(&api(C::AccountDisabled)));
        // One file the account may not touch says nothing about the session.
        assert!(!session_revoked(&api(C::Forbidden)));
        assert!(!session_revoked(&api(C::Timeout)));
        assert!(!session_revoked(&ProtonError::KeysLocked));
    }

    #[test]
    fn only_code_2028_is_a_blocked_sign_in() {
        assert!(sign_in_blocked(&api(C::Blocked)));
        assert!(!sign_in_blocked(&api(C::OutdatedApp)));
        assert!(!sign_in_blocked(&api(C::TooManyRequests)));
        assert!(!sign_in_blocked(&ProtonError::KeysLocked));
    }

    /// The regression this whole pass exists to prevent: before it, every SDK
    /// failure was hardcoded to `Remote`, so a 403 asked the user to retry a
    /// request that could never succeed.
    #[test]
    fn a_forbidden_response_is_not_offered_as_retryable() {
        let e = CoreError::from_api(&api(C::Forbidden), "rename");
        assert_eq!(e.kind, ErrorKind::Denied);
        assert!(!e.kind.retryable());
        assert!(e.message.starts_with("rename: "));
    }

    /// Being full is not a transient condition, so retrying an upload that did
    /// not fit must not be offered as a fix.
    #[test]
    fn running_out_of_space_is_not_retryable() {
        assert!(
            !CoreError::from_api(&api(C::InsufficientQuota), "upload")
                .kind
                .retryable()
        );
    }

    /// A failure that never reached the API is the user's connection, not
    /// Proton refusing — the front-end words those differently.
    #[test]
    fn a_transport_failure_reads_as_offline() {
        let io = std::io::Error::other("connection reset");
        assert_eq!(CoreError::from_api(&io, "list").kind, ErrorKind::Offline);
    }

    /// Issue #38: the SDK refused a photo upload before sending it, and the
    /// app said "You're offline" while every other call went through.
    #[test]
    fn a_call_the_sdk_refuses_to_send_is_not_offline() {
        let refused = ProtonError::invalid_operation("account has no photos volume");
        let e = CoreError::from_api(&refused, "upload photo failed");
        assert_eq!(e.kind, ErrorKind::Invalid);
        assert!(e.message.ends_with("account has no photos volume"));
        let e: CoreError = Error::Proton(ProtonError::KeysLocked).into();
        assert_ne!(e.kind, ErrorKind::Offline);
    }

    /// A pin or a search that fails on the database is not the connection, so
    /// it must not say "You're offline" (`docs/BUGS.md` B266). An SDK error
    /// wrapped in this crate's type classifies as the SDK error does.
    #[test]
    fn a_database_error_handed_to_from_api_is_not_offline() {
        let db = Error::Other("database is locked".into());
        assert_eq!(CoreError::from_api(&db, "pin").kind, ErrorKind::Internal);
        let wrapped = Error::Proton(api(C::DoesNotExist));
        assert_eq!(
            CoreError::from_api(&wrapped, "load node").kind,
            ErrorKind::NotFound
        );
    }

    /// `Error` is the plumbing type; converting it must classify as sharply as
    /// the direct path, or the two disagree about the same failure.
    #[test]
    fn converting_from_the_plumbing_error_classifies_the_api_code() {
        let e: CoreError = Error::Proton(api(C::DoesNotExist)).into();
        assert_eq!(e.kind, ErrorKind::NotFound);
    }
}