//! The limits a scope string is read under, and every way reading one fails.

/// The longest scope string [`ScopeSet::parse`](crate::ScopeSet::parse) reads. A real request is a
/// few hundred bytes.
pub const MAX_SCOPE_BYTES: usize = 16 * 1024;

/// The most scopes a string [`ScopeSet::parse`](crate::ScopeSet::parse) reads may name. An atom
/// that lists several collections or methods names one for each.
/// [`ScopeSet::new`](crate::ScopeSet::new) compares every pair of scopes, so this also bounds its
/// cost.
pub const MAX_SCOPE_ATOMS: usize = 128;

/// The longest grant [`ScopeSet::parse_grant`](crate::ScopeSet::parse_grant) reads: a request with
/// each `include:` replaced by the atoms its permission set grants.
///
/// Four times [`MAX_SCOPE_BYTES`]. `app.bsky.authFullApp` alone grants 115
/// atoms, about 9 KiB of them.
pub const MAX_GRANT_BYTES: usize = 64 * 1024;

/// The most atoms [`ScopeSet::parse_grant`](crate::ScopeSet::parse_grant) reads. Four times
/// [`MAX_SCOPE_ATOMS`], for the same reason as [`MAX_GRANT_BYTES`].
pub const MAX_GRANT_ATOMS: usize = 512;

/// The longest atom [`Scope::parse`](crate::Scope::parse) reads: room for a longest NSID (317
/// bytes) with a longest DID (2048 bytes) as its `aud`.
pub const MAX_ATOM_BYTES: usize = 4096;

/// A failure parsing one scope atom or a whole scope string.
#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
pub enum ScopeParseError {
    /// The scope string is longer than the bound it was read under:
    /// [`MAX_SCOPE_BYTES`] for a request, [`MAX_GRANT_BYTES`] for a grant.
    #[error("scope is {len} bytes, over the limit of {max}")]
    TooLong {
        /// How long the string is.
        len: usize,
        /// The bound it was read under.
        max: usize,
    },
    /// The scope string names more scopes than the bound it was read under:
    /// [`MAX_SCOPE_ATOMS`] for a request, [`MAX_GRANT_ATOMS`] for a grant.
    #[error("scope names {count} scopes, over the limit of {max}")]
    TooManyAtoms {
        /// How many scopes the string names.
        count: usize,
        /// The bound it was read under.
        max: usize,
    },
    /// An atom is longer than [`MAX_ATOM_BYTES`].
    #[error("a scope atom is {0} bytes, over the limit of {MAX_ATOM_BYTES}")]
    AtomTooLong(usize),
    /// An atom holds a character outside RFC 6749's `scope-token`: printable
    /// ASCII except `"` and `\`.
    #[error("a scope atom holds the character {0:?}, which a scope may not")]
    ForbiddenCharacter(char),
    /// The atom was the empty string.
    #[error("empty scope atom")]
    Empty,
    /// The `kind:` prefix is not one this grammar defines.
    #[error("`{0}` is not a recognised scope kind")]
    UnknownKind(String),
    /// The collection or method value is not a valid NSID or NSID wildcard.
    #[error("`{0}` is not a well-formed NSID or NSID wildcard")]
    MalformedNsid(String),
    /// The MIME value is not `type/subtype`, with either half a `*`.
    #[error("`{0}` is not a well-formed MIME type or MIME wildcard")]
    MalformedMime(String),
    /// An `action=` value the atom's kind does not define.
    #[error("`{0}` is not a recognised action")]
    UnknownAction(String),
    /// An `attr` value the atom's kind does not define.
    #[error("`{0}` is not a recognised attribute")]
    UnknownAttribute(String),
    /// [`Scope::parse`](crate::Scope::parse) was given an atom that names
    /// several scopes, one for each collection or method it lists.
    #[error("`{0}` names more than one scope")]
    SeveralScopes(String),
    /// A `transition:` atom named something other than the three defined
    /// legacy scopes.
    #[error("`{0}` is not a recognised transition scope")]
    UnknownTransition(String),
    /// The atom gave no value for the parameter its kind requires, such as
    /// `repo:`'s collection. An `include:` whose value names no permission
    /// set still parses; see [`Include::new`](crate::Include::new).
    #[error("`{0}` is missing the value its kind requires")]
    MissingValue(String),
    /// A `?query` segment had a pair with no `=`.
    #[error("`{0}` in the query string of `{1}` is not `k=v`")]
    MalformedQuery(String, String),
}