// Package checker implements a TLS checker for happyDomain. See README for
// the payload shape and consumer contract.
package checker

import "time"

// ObservationKeyTLSProbes is the observation key this checker writes.
const ObservationKeyTLSProbes = "tls_probes"

// Option ids on CheckerOptions.
const (
	OptionEndpoints      = "endpoints"
	OptionProbeTimeoutMs = "probeTimeoutMs"
)

// Defaults shared between the definition's Default field and the runtime
// fallback when probeTimeoutMs is unset or invalid.
const (
	DefaultProbeTimeoutMs = 10000
	// MaxConcurrentProbes caps parallel probes per collect run to avoid
	// exhausting file descriptors on domains with many endpoints.
	MaxConcurrentProbes = 32
)

// TLSData is the full collected payload written under ObservationKeyTLSProbes.
type TLSData struct {
	Probes      map[string]TLSProbe `json:"probes"`
	CollectedAt time.Time           `json:"collected_at"`
}

// TLSProbe captures the outcome of probing a single endpoint.
//
// Only raw observation fields live here. Judgement (severity, pass/fail,
// human-facing messages) is derived from these fields by CheckRules.
type TLSProbe struct {
	Host     string `json:"host"`
	Port     uint16 `json:"port"`
	Endpoint string `json:"endpoint"`
	Type     string `json:"type"`
	SNI      string `json:"sni,omitempty"`

	// RequireSTARTTLS is copied from the discovery entry so rules can tell
	// whether a missing STARTTLS advertisement is a hard or soft failure.
	RequireSTARTTLS bool `json:"require_starttls,omitempty"`

	// STARTTLSDialect mirrors contract.TLSEndpoint.STARTTLS verbatim. An
	// empty value means direct TLS.
	STARTTLSDialect string `json:"starttls_dialect,omitempty"`

	// Raw error strings. Exactly one of TCPError or HandshakeError is set
	// when the probe failed before gathering handshake data.
	TCPError       string `json:"tcp_error,omitempty"`
	HandshakeError string `json:"handshake_error,omitempty"`

	// STARTTLSNotOffered is true when HandshakeError was produced because
	// the server did not advertise STARTTLS (errStartTLSNotOffered).
	STARTTLSNotOffered bool `json:"starttls_not_offered,omitempty"`

	// STARTTLSUnsupportedProto is true when the STARTTLS dialect is not
	// implemented by this checker.
	STARTTLSUnsupportedProto bool `json:"starttls_unsupported_proto,omitempty"`

	// TLSHandshakeOK is true when a TLS handshake completed. It is
	// independent from chain validity.
	TLSHandshakeOK bool `json:"tls_handshake_ok,omitempty"`

	// TLSVersionNum is the numeric TLS version negotiated (uint16 from
	// crypto/tls). Zero means no handshake occurred. Kept as an unsigned
	// integer so rules can compare against tls.VersionTLS12 without
	// re-parsing a string.
	TLSVersionNum uint16 `json:"tls_version_num,omitempty"`

	TLSVersion    string `json:"tls_version,omitempty"`
	CipherSuite   string `json:"cipher_suite,omitempty"`
	CipherSuiteID uint16 `json:"cipher_suite_id,omitempty"`

	// NoPeerCert is true when the handshake succeeded but the server sent
	// no certificate.
	NoPeerCert bool `json:"no_peer_cert,omitempty"`

	HostnameMatch  *bool     `json:"hostname_match,omitempty"`
	ChainValid     *bool     `json:"chain_valid,omitempty"`
	ChainVerifyErr string    `json:"chain_verify_err,omitempty"`
	NotAfter       time.Time `json:"not_after,omitempty"`
	Issuer         string    `json:"issuer,omitempty"`
	// IssuerDN is the leaf's issuer as an RFC 2253 DN string, suitable for
	// matching the CCADB CAA Identifiers CSV "Subject" column when the AKI
	// lookup misses.
	IssuerDN string `json:"issuer_dn,omitempty"`
	// IssuerAKI is the uppercase hex of the leaf's Authority Key Identifier
	// extension (i.e. the issuer cert's SKI). This is the primary lookup key
	// into the CCADB CAA Identifiers CSV ("Subject Key Identifier (Hex)").
	IssuerAKI string   `json:"issuer_aki,omitempty"`
	Subject   string   `json:"subject,omitempty"`
	DNSNames  []string `json:"dns_names,omitempty"`
	// Chain carries one entry per certificate presented by the server
	// (leaf first, then intermediates in order). Each entry precomputes
	// the four TLSA selector×matching_type hashes plus the raw DER so
	// DANE consumers can match without re-handshaking or re-parsing.
	Chain     []CertInfo `json:"chain,omitempty"`
	ElapsedMS int64      `json:"elapsed_ms,omitempty"`

	// Error is a compatibility summary of whichever raw error applies.
	// Left for any external consumer still inspecting it; rules should
	// look at TCPError / HandshakeError instead.
	Error string `json:"error,omitempty"`
}

// CertInfo describes one certificate in the presented chain together with
// pre-hashed forms suitable for DANE/TLSA matching (RFC 6698 §2.1).
//
// Hex fields are lowercase, matching the representation emitted by
// miekg/dns for TLSA RR Certificate fields.
type CertInfo struct {
	// DERBase64 is the standard base64 encoding of the certificate's DER
	// form. Carried so consumers can do matching-type 0 (Full) without
	// requiring a precomputed "full" hash and for fallback inspection.
	DERBase64 string `json:"der_base64,omitempty"`

	// Subject / Issuer are short human-readable DNs for the HTML report.
	Subject string `json:"subject,omitempty"`
	Issuer  string `json:"issuer,omitempty"`

	// NotAfter is the certificate's expiry. Carried so editors can show
	// "expires on …" without re-parsing the DER.
	NotAfter time.Time `json:"not_after,omitempty"`

	// Selector 0 = full certificate.
	CertSHA256 string `json:"cert_sha256,omitempty"`
	CertSHA512 string `json:"cert_sha512,omitempty"`

	// Selector 1 = SubjectPublicKeyInfo.
	SPKISHA256 string `json:"spki_sha256,omitempty"`
	SPKISHA512 string `json:"spki_sha512,omitempty"`

	// SPKIDERBase64 lets consumers handle (selector=1, matching=0) without
	// re-parsing the certificate.
	SPKIDERBase64 string `json:"spki_der_base64,omitempty"`
}

// Expiry thresholds shared by rules.
const (
	ExpiringSoonThreshold = 14 * 24 * time.Hour
)