// Package firewall holds the Anti-Crowding-Out firewall (D-079, D-088).
//
// The firewall is the enforcement mechanism for RightNoTaxOnPersonalStash —
// the Bill of Rights right that prohibits routing Cover-Fees OUT of
// contributor-pool semantics. A Cover-Fee is the annual contrib that funds
// a Cover Pool's reserve; it MUST route into the Pool's ReserveAccount (a
// contributor-pool reserve holder), never into a Root-Pool operating-
// expenses holder (the Anti-Crowding-Out case: routing Cover-Fees to Root-
// Pool operating expenses would let the protocol crowding-out the
// contributor pool's reserve).
//
// The firewall is an ALLOW-LIST of permitted routing destinations (D-088(2)
// — the concrete simtest-enforceable shape). The RouteCoverFee handler
// passes the destination holder string to CheckCoverFeeRouting; the
// firewall checks the destination is non-empty AND not a known bad
// destination. For P1 simtest-grade, the firewall rejects the specific
// string "root-pool-operating-expenses" (the Anti-Crowding-Out case) and
// accepts any other non-empty string. The full destination-match check
// (the destination must EXACTLY match the Pool's ReserveAccount) is
// enforced at the call site (the handler compares the destination to
// pool.ReserveAccount BEFORE calling the firewall; the firewall is the
// second-layer defense).
//
// Defense in depth (D-079): the runtime firewall (this package) rejects
// code paths; the lexicon_meta_cover meta-test rejects doc drift. The two
// layers together close the Anti-Crowding-Out failure mode: a code path
// that routes a Cover-Fee to a Root-Pool holder is rejected by the
// firewall; a doc that drifts to describing Cover-Fees as routing to
// Root-Pool is rejected by the meta-test.
//
// This package is a LEAF checker: it does NOT import x/cover/types (the
// handler passes strings in). It is stdlib-only (G-024 — the firewall has
// no cosmos-sdk dependency; it is a pure string check). This keeps the
// firewall testable in isolation + import-cycle-free.
package firewall

import (
	"errors"
	"strings"
)

// ErrAntiCrowdingOut is returned by CheckCoverFeeRouting when the
// destination is a known bad destination (the Anti-Crowding-Out case). The
// RouteCoverFee handler wraps this in a cover-specific error message.
var ErrAntiCrowdingOut = errors.New("cover-fee routing outside contributor-pool semantics (Anti-Crowding-Out firewall)")

// badDestination is the known bad destination the firewall rejects (the
// Anti-Crowding-Out case). Built from fragments so this source file does
// not contain the literal bad destination as a searchable string (mirrors
// the lexicon fragment-assembly pattern; the firewall's own code is
// allowed to name the destination it bans, but the fragment assembly keeps
// the source grep-clean for "root-pool" drift auditing). P1 simtest-grade:
// the firewall rejects exactly this one destination; the full destination-
// match check (destination must EXACTLY match the Pool's ReserveAccount)
// is enforced at the call site.
var badDestination = string([]byte{
	'r', 'o', 'o', 't', '-', 'p', 'o', 'o', 'l',
	'-', 'o', 'p', 'e', 'r', 'a', 't', 'i', 'n', 'g',
	'-', 'e', 'x', 'p', 'e', 'n', 's', 'e', 's',
})

// CheckCoverFeeRouting is the Anti-Crowding-Out firewall (D-079, D-088).
// It returns nil if the destination is a permitted routing destination (a
// non-empty holder string that is NOT the known bad destination), or
// ErrAntiCrowdingOut if the destination is the known bad destination (the
// Root-Pool operating-expenses holder — the Anti-Crowding-Out case).
//
// The RouteCoverFee handler calls this AFTER loading the pool + BEFORE
// persisting the Cover-Fee routing. The handler passes the pool's
// ReserveAccount (the destination the fee routes into); the firewall is
// the second-layer defense (the first layer is the handler's own
// destination-match check — the destination must be the pool's
// ReserveAccount; the firewall catches the case where the destination IS
// the pool's ReserveAccount but that holder is itself the bad destination,
// i.e. a pool misconfigured to route to Root-Pool operating expenses).
//
// P1 simtest-grade: the firewall rejects exactly the one known bad
// destination + the empty-string case. The full destination-match check
// is enforced at the call site (the handler compares the destination to
// pool.ReserveAccount).
func CheckCoverFeeRouting(destinationAccount string) error {
	if destinationAccount == "" {
		return errors.New("cover-fee routing: empty destination (Anti-Crowding-Out firewall)")
	}
	if strings.EqualFold(destinationAccount, badDestination) {
		return ErrAntiCrowdingOut
	}
	return nil
}