txscript

const (
	// ErrInternal is returned if internal consistency checks fail.  In
	// practice this error should never be seen as it would mean there is an
	// error in the engine logic.
	ErrInternal ErrorCode = iota

	// ErrInvalidFlags is returned when the passed flags to NewEngine
	// contain an invalid combination.
	ErrInvalidFlags

	// ErrInvalidIndex is returned when an out-of-bounds index is passed to
	// a function.
	ErrInvalidIndex

	// ErrUnsupportedAddress is returned when a concrete type that
	// implements a btcutil.Address is not a supported type.
	ErrUnsupportedAddress

	// ErrNotMultisigScript is returned from CalcMultiSigStats when the
	// provided script is not a multisig script.
	ErrNotMultisigScript

	// ErrTooManyRequiredSigs is returned from MultiSigScript when the
	// specified number of required signatures is larger than the number of
	// provided public keys.
	ErrTooManyRequiredSigs

	// ErrTooMuchNullData is returned from NullDataScript when the length of
	// the provided data exceeds MaxDataCarrierSize.
	ErrTooMuchNullData

	// ErrUnsupportedScriptVersion is returned when an unsupported script
	// version is passed to a function which deals with script analysis.
	ErrUnsupportedScriptVersion

	// ErrEarlyReturn is returned when OP_RETURN is executed in the script.
	ErrEarlyReturn

	// ErrEmptyStack is returned when the script evaluated without error,
	// but terminated with an empty top stack element.
	ErrEmptyStack

	// ErrEvalFalse is returned when the script evaluated without error but
	// terminated with a false top stack element.
	ErrEvalFalse

	// ErrScriptUnfinished is returned when CheckErrorCondition is called on
	// a script that has not finished executing.
	ErrScriptUnfinished

	// ErrScriptDone is returned when an attempt to execute an opcode is
	// made once all of them have already been executed.  This can happen
	// due to things such as a second call to Execute or calling Step after
	// all opcodes have already been executed.
	ErrInvalidProgramCounter

	// ErrScriptTooBig is returned if a script is larger than MaxScriptSize.
	ErrScriptTooBig

	// ErrElementTooBig is returned if the size of an element to be pushed
	// to the stack is over MaxScriptElementSize.
	ErrElementTooBig

	// ErrTooManyOperations is returned if a script has more than
	// MaxOpsPerScript opcodes that do not push data.
	ErrTooManyOperations

	// ErrStackOverflow is returned when stack and altstack combined depth
	// is over the limit.
	ErrStackOverflow

	// ErrInvalidPubKeyCount is returned when the number of public keys
	// specified for a multsig is either negative or greater than
	// MaxPubKeysPerMultiSig.
	ErrInvalidPubKeyCount

	// ErrInvalidSignatureCount is returned when the number of signatures
	// specified for a multisig is either negative or greater than the
	// number of public keys.
	ErrInvalidSignatureCount

	// ErrNumberTooBig is returned when the argument for an opcode that
	// expects numeric input is larger than the expected maximum number of
	// bytes.  For the most part, opcodes that deal with stack manipulation
	// via offsets, arithmetic, numeric comparison, and boolean logic are
	// those that this applies to.  However, any opcode that expects numeric
	// input may fail with this code.
	ErrNumberTooBig

	// ErrVerify is returned when OP_VERIFY is encountered in a script and
	// the top item on the data stack does not evaluate to true.
	ErrVerify

	// ErrEqualVerify is returned when OP_EQUALVERIFY is encountered in a
	// script and the top item on the data stack does not evaluate to true.
	ErrEqualVerify

	// ErrNumEqualVerify is returned when OP_NUMEQUALVERIFY is encountered
	// in a script and the top item on the data stack does not evaluate to
	// true.
	ErrNumEqualVerify

	// ErrCheckSigVerify is returned when OP_CHECKSIGVERIFY is encountered
	// in a script and the top item on the data stack does not evaluate to
	// true.
	ErrCheckSigVerify

	// ErrCheckSigVerify is returned when OP_CHECKMULTISIGVERIFY is
	// encountered in a script and the top item on the data stack does not
	// evaluate to true.
	ErrCheckMultiSigVerify

	// ErrDisabledOpcode is returned when a disabled opcode is encountered
	// in a script.
	ErrDisabledOpcode

	// ErrReservedOpcode is returned when an opcode marked as reserved
	// is encountered in a script.
	ErrReservedOpcode

	// ErrMalformedPush is returned when a data push opcode tries to push
	// more bytes than are left in the script.
	ErrMalformedPush

	// ErrInvalidStackOperation is returned when a stack operation is
	// attempted with a number that is invalid for the current stack size.
	ErrInvalidStackOperation

	// ErrUnbalancedConditional is returned when an OP_ELSE or OP_ENDIF is
	// encountered in a script without first having an OP_IF or OP_NOTIF or
	// the end of script is reached without encountering an OP_ENDIF when
	// an OP_IF or OP_NOTIF was previously encountered.
	ErrUnbalancedConditional

	// ErrMinimalData is returned when the ScriptVerifyMinimalData flag
	// is set and the script contains push operations that do not use
	// the minimal opcode required.
	ErrMinimalData

	// ErrInvalidSigHashType is returned when a signature hash type is not
	// one of the supported types.
	ErrInvalidSigHashType

	// ErrSigTooShort is returned when a signature that should be a
	// canonically-encoded DER signature is too short.
	ErrSigTooShort

	// ErrSigTooLong is returned when a signature that should be a
	// canonically-encoded DER signature is too long.
	ErrSigTooLong

	// ErrSigInvalidSeqID is returned when a signature that should be a
	// canonically-encoded DER signature does not have the expected ASN.1
	// sequence ID.
	ErrSigInvalidSeqID

	// ErrSigInvalidDataLen is returned a signature that should be a
	// canonically-encoded DER signature does not specify the correct number
	// of remaining bytes for the R and S portions.
	ErrSigInvalidDataLen

	// ErrSigMissingSTypeID is returned a signature that should be a
	// canonically-encoded DER signature does not provide the ASN.1 type ID
	// for S.
	ErrSigMissingSTypeID

	// ErrSigMissingSLen is returned when a signature that should be a
	// canonically-encoded DER signature does not provide the length of S.
	ErrSigMissingSLen

	// ErrSigInvalidSLen is returned a signature that should be a
	// canonically-encoded DER signature does not specify the correct number
	// of bytes for the S portion.
	ErrSigInvalidSLen

	// ErrSigInvalidRIntID is returned when a signature that should be a
	// canonically-encoded DER signature does not have the expected ASN.1
	// integer ID for R.
	ErrSigInvalidRIntID

	// ErrSigZeroRLen is returned when a signature that should be a
	// canonically-encoded DER signature has an R length of zero.
	ErrSigZeroRLen

	// ErrSigNegativeR is returned when a signature that should be a
	// canonically-encoded DER signature has a negative value for R.
	ErrSigNegativeR

	// ErrSigTooMuchRPadding is returned when a signature that should be a
	// canonically-encoded DER signature has too much padding for R.
	ErrSigTooMuchRPadding

	// ErrSigInvalidSIntID is returned when a signature that should be a
	// canonically-encoded DER signature does not have the expected ASN.1
	// integer ID for S.
	ErrSigInvalidSIntID

	// ErrSigZeroSLen is returned when a signature that should be a
	// canonically-encoded DER signature has an S length of zero.
	ErrSigZeroSLen

	// ErrSigNegativeS is returned when a signature that should be a
	// canonically-encoded DER signature has a negative value for S.
	ErrSigNegativeS

	// ErrSigTooMuchSPadding is returned when a signature that should be a
	// canonically-encoded DER signature has too much padding for S.
	ErrSigTooMuchSPadding

	// ErrSigHighS is returned when the ScriptVerifyLowS flag is set and the
	// script contains any signatures whose S values are higher than the
	// half order.
	ErrSigHighS

	// ErrNotPushOnly is returned when a script that is required to only
	// push data to the stack performs other operations.  A couple of cases
	// where this applies is for a pay-to-script-hash signature script when
	// bip16 is active and when the ScriptVerifySigPushOnly flag is set.
	ErrNotPushOnly

	// ErrSigNullDummy is returned when the ScriptStrictMultiSig flag is set
	// and a multisig script has anything other than 0 for the extra dummy
	// argument.
	ErrSigNullDummy

	// ErrPubKeyType is returned when the ScriptVerifyStrictEncoding
	// flag is set and the script contains invalid public keys.
	ErrPubKeyType

	// ErrCleanStack is returned when the ScriptVerifyCleanStack flag
	// is set, and after evalution, the stack does not contain only a
	// single element.
	ErrCleanStack

	// ErrNullFail is returned when the ScriptVerifyNullFail flag is
	// set and signatures are not empty on failed checksig or checkmultisig
	// operations.
	ErrNullFail

	// ErrWitnessMalleated is returned if ScriptVerifyWitness is set and a
	// native p2wsh program is encountered which has a non-empty sigScript.
	ErrWitnessMalleated

	// ErrWitnessMalleatedP2SH is returned if ScriptVerifyWitness if set
	// and the validation logic for nested p2sh encounters a sigScript
	// which isn't *exactyl* a datapush of the witness program.
	ErrWitnessMalleatedP2SH

	// ErrDiscourageUpgradableNOPs is returned when the
	// ScriptDiscourageUpgradableNops flag is set and a NOP opcode is
	// encountered in a script.
	ErrDiscourageUpgradableNOPs

	// ErrNegativeLockTime is returned when a script contains an opcode that
	// interprets a negative lock time.
	ErrNegativeLockTime

	// ErrUnsatisfiedLockTime is returned when a script contains an opcode
	// that involves a lock time and the required lock time has not been
	// reached.
	ErrUnsatisfiedLockTime

	// ErrMinimalIf is returned if ScriptVerifyWitness is set and the
	// operand of an OP_IF/OP_NOF_IF are not either an empty vector or
	// [0x01].
	ErrMinimalIf

	// ErrDiscourageUpgradableWitnessProgram is returned if
	// ScriptVerifyWitness is set and the versino of an executing witness
	// program is outside the set of currently defined witness program
	// vesions.
	ErrDiscourageUpgradableWitnessProgram

	// ErrWitnessProgramEmpty is returned if ScriptVerifyWitness is set and
	// the witness stack itself is empty.
	ErrWitnessProgramEmpty

	// ErrWitnessProgramMismatch is returned if ScriptVerifyWitness is set
	// and the witness itself for a p2wkh witness program isn't *exactly* 2
	// items or if the witness for a p2wsh isn't the sha255 of the witness
	// script.
	ErrWitnessProgramMismatch

	// ErrWitnessProgramWrongLength is returned if ScriptVerifyWitness is
	// set and the length of the witness program violates the length as
	// dictated by the current witness version.
	ErrWitnessProgramWrongLength

	// ErrWitnessUnexpected is returned if ScriptVerifyWitness is set and a
	// transaction includes witness data but doesn't spend an which is a
	// witness program (nested or native).
	ErrWitnessUnexpected

	// ErrWitnessPubKeyType is returned if ScriptVerifyWitness is set and
	// the public key used in either a check-sig or check-multi-sig isn't
	// serialized in a compressed format.
	ErrWitnessPubKeyType

	// ErrDiscourageOpSuccess is returned if
	// ScriptVerifyDiscourageOpSuccess is active, and a OP_SUCCESS op code
	// is encountered during tapscript validation.
	ErrDiscourageOpSuccess

	// ErrDiscourageUpgradeableTaprootVersion is returned if
	// ScriptVerifyDiscourageUpgradeableTaprootVersion is active and a leaf
	// version encountered isn't the base leaf version.
	ErrDiscourageUpgradeableTaprootVersion

	// ErrTapscriptCheckMultisig is returned if a script attempts to use
	// OP_CHECKMULTISIGVERIFY or OP_CHECKMULTISIG during tapscript
	// execution.
	ErrTapscriptCheckMultisig

	// ErrDiscourageUpgradeableTaprootVersion is returned if during
	// tapscript execution, we encoutner a public key that isn't 0 or 32
	// bytes.
	ErrDiscourageUpgradeablePubKeyType

	// ErrTaprootSigInvalid is returned when an invalid taproot key spend
	// signature is encountered.
	ErrTaprootSigInvalid

	// ErrTaprootMerkleProofInvalid is returned when the revealed script
	// merkle proof for a taproot spend is found to be invalid.
	ErrTaprootMerkleProofInvalid

	// ErrTaprootOutputKeyParityMismatch is returned when the control block
	// proof is valid, but the parity of the y-coordinate of the derived
	// key doesn't match the value encoded in the control block.
	ErrTaprootOutputKeyParityMismatch

	// ErrControlBlockTooSmall is returned when a parsed control block is
	// less than 33 bytes.
	ErrControlBlockTooSmall

	// ErrControlBlockTooLarge is returned when the control block is larger
	// than the largest possible proof for a merkle script tree.
	ErrControlBlockTooLarge

	// ErrControlBlockInvalidLength is returned when the control block,
	// without the public key isn't a multiple of 32.
	ErrControlBlockInvalidLength

	// ErrWitnessHasNoAnnex is returned when a caller attempts to extract
	// an annex, but the witness has no annex present.
	ErrWitnessHasNoAnnex

	// ErrInvalidTaprootSigLen is returned when taproot signature isn't 64
	// or 65 bytes.
	ErrInvalidTaprootSigLen

	// ErrTaprootPubkeyIsEmpty is returned when a signature checking op
	// code encounters an empty public key.
	ErrTaprootPubkeyIsEmpty

	// ErrTaprootMaxSigOps is returned when the number of allotted sig ops
	// is exceeded during taproot execution.
	ErrTaprootMaxSigOps
)

const (
	NonStandardTy         ScriptClass = iota // None of the recognized forms.
	PubKeyTy                                 // Pay pubkey.
	PubKeyHashTy                             // Pay pubkey hash.
	WitnessV0PubKeyHashTy                    // Pay witness pubkey hash.
	ScriptHashTy                             // Pay to script hash.
	WitnessV0ScriptHashTy                    // Pay to witness script hash.
	MultiSigTy                               // Multi signature.
	NullDataTy                               // Empty data-only (provably prunable).
	WitnessV1TaprootTy                       // Taproot output
	WitnessUnknownTy                         // Witness unknown
)

const (
	// ScriptBip16 defines whether the bip16 threshold has passed and thus
	// pay-to-script hash transactions will be fully validated.
	ScriptBip16 ScriptFlags = 1 << iota

	// ScriptStrictMultiSig defines whether to verify the stack item
	// used by CHECKMULTISIG is zero length.
	ScriptStrictMultiSig

	// ScriptDiscourageUpgradableNops defines whether to verify that
	// NOP1 through NOP10 are reserved for future soft-fork upgrades.  This
	// flag must not be used for consensus critical code nor applied to
	// blocks as this flag is only for stricter standard transaction
	// checks.  This flag is only applied when the above opcodes are
	// executed.
	ScriptDiscourageUpgradableNops

	// ScriptVerifyCheckLockTimeVerify defines whether to verify that
	// a transaction output is spendable based on the locktime.
	// This is BIP0065.
	ScriptVerifyCheckLockTimeVerify

	// ScriptVerifyCheckSequenceVerify defines whether to allow execution
	// pathways of a script to be restricted based on the age of the output
	// being spent.  This is BIP0112.
	ScriptVerifyCheckSequenceVerify

	// ScriptVerifyCleanStack defines that the stack must contain only
	// one stack element after evaluation and that the element must be
	// true if interpreted as a boolean.  This is rule 6 of BIP0062.
	// This flag should never be used without the ScriptBip16 flag nor the
	// ScriptVerifyWitness flag.
	ScriptVerifyCleanStack

	// ScriptVerifyDERSignatures defines that signatures are required
	// to compily with the DER format.
	ScriptVerifyDERSignatures

	// ScriptVerifyLowS defines that signtures are required to comply with
	// the DER format and whose S value is <= order / 2.  This is rule 5
	// of BIP0062.
	ScriptVerifyLowS

	// ScriptVerifyMinimalData defines that signatures must use the smallest
	// push operator. This is both rules 3 and 4 of BIP0062.
	ScriptVerifyMinimalData

	// ScriptVerifyNullFail defines that signatures must be empty if
	// a CHECKSIG or CHECKMULTISIG operation fails.
	ScriptVerifyNullFail

	// ScriptVerifySigPushOnly defines that signature scripts must contain
	// only pushed data.  This is rule 2 of BIP0062.
	ScriptVerifySigPushOnly

	// ScriptVerifyStrictEncoding defines that signature scripts and
	// public keys must follow the strict encoding requirements.
	ScriptVerifyStrictEncoding

	// ScriptVerifyWitness defines whether or not to verify a transaction
	// output using a witness program template.
	ScriptVerifyWitness

	// ScriptVerifyDiscourageUpgradeableWitnessProgram makes witness
	// program with versions 2-16 non-standard.
	ScriptVerifyDiscourageUpgradeableWitnessProgram

	// ScriptVerifyMinimalIf makes a script with an OP_IF/OP_NOTIF whose
	// operand is anything other than empty vector or [0x01] non-standard.
	ScriptVerifyMinimalIf

	// ScriptVerifyWitnessPubKeyType makes a script within a check-sig
	// operation whose public key isn't serialized in a compressed format
	// non-standard.
	ScriptVerifyWitnessPubKeyType

	// ScriptVerifyTaproot defines whether or not to verify a transaction
	// output using the new taproot validation rules.
	ScriptVerifyTaproot

	// ScriptVerifyDiscourageUpgradeableWitnessProgram defines whether or
	// not to consider any new/unknown taproot leaf versions as
	// non-standard.
	ScriptVerifyDiscourageUpgradeableTaprootVersion

	// ScriptVerifyDiscourageOpSuccess defines whether or not to consider
	// usage of OP_SUCCESS op codes during tapscript execution as
	// non-standard.
	ScriptVerifyDiscourageOpSuccess

	// ScriptVerifyDiscourageUpgradeablePubkeyType defines if unknown
	// public key versions (during tapscript execution) is non-standard.
	ScriptVerifyDiscourageUpgradeablePubkeyType
)

const (
	SigHashDefault      SigHashType = 0x00
	SigHashOld          SigHashType = 0x0
	SigHashAll          SigHashType = 0x1
	SigHashNone         SigHashType = 0x2
	SigHashSingle       SigHashType = 0x3
	SigHashAnyOneCanPay SigHashType = 0x80
)

const (
	// BaseLeafVersion is the base tapscript leaf version. The semantics of
	// this version are defined in BIP 342.
	BaseLeafVersion TapscriptLeafVersion = 0xc0
)