// Package datekeys is the reference Go implementation of the DateKeys Protocol
// Specification v0.9 (spec/DateKeys_Protocol_Specification_v0.9.md).
//
// The protocol objects live in subpackages:
//
//   - datekey: DateKey resolution and the canonical dk1_ form (spec §14-§19).
//   - profile: Provider Profiles and the pinned Quicknet profile (spec §10-§13).
//   - provider, provider/drand: release sources and local BLS verification (spec §45-§52).
//   - capsule: the DateKeyCap .dkc container (spec §20-§39, §61-§63).
//   - accesskey: the DateKeys Access Key .dkk credential (spec §40-§44).
//   - extension: the generic extension mechanism (spec §54).
//
// This package holds the normative error catalogue of spec §69. Every protocol
// failure returned by this module wraps exactly one of these sentinels, so
// callers can match them with [errors.Is] and extract the code with [Code].
package datekeys

import "errors"

// Error is a normative DateKeys error (spec §69). Values are compared by
// identity; use [errors.Is] against the exported sentinels.
type Error struct {
	code string
}

// Error returns the normative code, for example "ERR_INVALID_MAGIC".
func (e *Error) Error() string { return e.code }

// Code returns the normative code, for example "ERR_INVALID_MAGIC".
func (e *Error) Code() string { return e.code }

// Normative errors, spec §69.
var (
	// ErrInvalidMagic: the object does not start with DKC1 or DKK1 (spec §22, §40).
	ErrInvalidMagic = &Error{"ERR_INVALID_MAGIC"}
	// ErrUnsupportedVersion: an unknown framing or schema version (spec §22, §70).
	ErrUnsupportedVersion = &Error{"ERR_UNSUPPORTED_VERSION"}
	// ErrInvalidFlags: FLAGS or RESERVED are not zero (spec §22, §40).
	ErrInvalidFlags = &Error{"ERR_INVALID_FLAGS"}
	// ErrNonCanonicalCBOR: the bytes are not the unique deterministic CBOR
	// encoding of a valid instance of the normative schema (spec §58, §58.1).
	ErrNonCanonicalCBOR = &Error{"ERR_NON_CANONICAL_CBOR"}
	// ErrUnknownProfile: the DateKey names a profile that is not pinned locally (spec §13).
	ErrUnknownProfile = &Error{"ERR_UNKNOWN_PROFILE"}
	// ErrProfileMismatch: a chain hash or profile does not match the pinned profile (spec §35, §63).
	ErrProfileMismatch = &Error{"ERR_PROFILE_MISMATCH"}
	// ErrDateKeyInvalid: a DateKey that cannot be decoded or validated (spec §18, §19).
	ErrDateKeyInvalid = &Error{"ERR_DATEKEY_INVALID"}
	// ErrDateKeyNonCanonical: a valid DateKey in a non-canonical encoding (spec §19).
	ErrDateKeyNonCanonical = &Error{"ERR_DATEKEY_NON_CANONICAL"}
	// ErrRoundMismatch: a round that differs from the locally resolved one (spec §17, §63).
	ErrRoundMismatch = &Error{"ERR_ROUND_MISMATCH"}
	// ErrReleaseUnavailable: the release is not published yet or no source delivered it (spec §45-§50).
	ErrReleaseUnavailable = &Error{"ERR_RELEASE_UNAVAILABLE"}
	// ErrReleaseInvalid: a release that fails local verification (spec §51).
	ErrReleaseInvalid = &Error{"ERR_RELEASE_INVALID"}
	// ErrAccessRequired: the policy requires an access credential and none was supplied (spec §33).
	ErrAccessRequired = &Error{"ERR_ACCESS_REQUIRED"}
	// ErrAccessInvalid: the supplied credentials do not open this capsule (spec §33, §38).
	ErrAccessInvalid = &Error{"ERR_ACCESS_INVALID"}
	// ErrPolicyStructureMismatch: the cryptographic structure does not match the
	// declared access policy or the stanza rules of V1 (spec §25, §29, §32, §33, §36).
	ErrPolicyStructureMismatch = &Error{"ERR_POLICY_STRUCTURE_MISMATCH"}
	// ErrHeaderBinding: header_binding does not match PRELUDE || PUBLIC_HEADER (spec §26).
	ErrHeaderBinding = &Error{"ERR_HEADER_BINDING"}
	// ErrIntegrity: truncation, corruption or failed authentication of framing or age data (spec §4, §55).
	ErrIntegrity = &Error{"ERR_INTEGRITY"}
	// ErrExtensionCriticalUnknown: a critical extension this implementation does not know (spec §54).
	ErrExtensionCriticalUnknown = &Error{"ERR_EXTENSION_CRITICAL_UNKNOWN"}
	// ErrExtensionDataInvalid: a known extension whose data does not follow its
	// registered schema. It rejects the object only for a critical extension; a
	// noncritical one is reported as unusable (spec §54, §72).
	ErrExtensionDataInvalid = &Error{"ERR_EXTENSION_DATA_INVALID"}
	// ErrHeadInvalid: the head of a format 3 capsule is well encoded but one
	// of its fields breaks its rules: a path, the comment, the declared author
	// or the layout of the files (spec §29.4 to §29.6). New in v0.10.
	ErrHeadInvalid = &Error{"ERR_HEAD_INVALID"}
)

// All returns every normative error in the order of spec §69.
func All() []*Error {
	return []*Error{
		ErrInvalidMagic, ErrUnsupportedVersion, ErrInvalidFlags, ErrNonCanonicalCBOR,
		ErrUnknownProfile, ErrProfileMismatch, ErrDateKeyInvalid, ErrDateKeyNonCanonical,
		ErrRoundMismatch, ErrReleaseUnavailable, ErrReleaseInvalid, ErrAccessRequired,
		ErrAccessInvalid, ErrPolicyStructureMismatch, ErrHeaderBinding, ErrIntegrity,
		ErrExtensionCriticalUnknown, ErrExtensionDataInvalid, ErrHeadInvalid,
	}
}

// Code returns the normative code of the first DateKeys error in err's tree,
// or "" if err does not wrap one.
func Code(err error) string {
	var e *Error
	if errors.As(err, &e) {
		return e.code
	}
	return ""
}