Capstone.idr

-- SPDX-License-Identifier: MPL-2.0
-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
--
||| Layer 5 — END-TO-END ABI SOUNDNESS CERTIFICATE for Affinescriptiser.
|||
||| This capstone does NOT prove a new domain theorem. It ASSEMBLES the proofs
||| already discharged in the lower layers into ONE inhabited record value. The
||| certificate ties the whole ABI contract together:
|||
|||   manifest (the affine-usage model: `Trace` / `AffineOk`)
|||     -> Layer 2 FLAGSHIP property : a single program fragment uses every
|||        variable at most once  (`AffineOk`, witnessed on the canonical
|||        positive-control instance `safeTraceAffineOk : AffineOk [0,1,2]`).
|||     -> Layer 3 INVARIANT : the composition law — sequencing two affine,
|||        variable-disjoint fragments stays affine  (`concatAffine`, witnessed
|||        on the canonical positive control `composedOk : AffineOk [0,1,2,3]`).
|||     -> Layer 4 FFI SEAM : the ABI<->C `Result` encoding is unambiguous, so
|||        distinct ABI outcomes never collide on the wire
|||        (`resultToIntInjective`).
|||
||| Each field below is filled ONLY from an already-`export`ed witness/theorem of
||| the modules it imports — nothing is re-proved or fabricated here. The single
||| value `abiContractDischarged : ABISound` is therefore the capstone: if ANY
||| prior layer were unsound (the flagship witness, the invariant witness, or the
||| seam injectivity), this value would fail to typecheck and the certificate
||| could not be issued. Genuine composition only: no believe_me, no idris_crash,
||| no assert_total, no postulate, no sorry, no %hint hacks, no asserted equality.

module Affinescriptiser.ABI.Capstone

import Affinescriptiser.ABI.Types
import Affinescriptiser.ABI.Semantics
import Affinescriptiser.ABI.Invariants
import Affinescriptiser.ABI.FfiSeam

%default total

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-- The certificate type
--------------------------------------------------------------------------------

||| `ABISound` records the KEY proven facts of the Affinescriptiser ABI, one
||| field per proof layer. Inhabiting it requires a genuine witness of each.
public export
record ABISound where
  constructor MkABISound
  ||| Layer 2 (flagship): the canonical positive-control program fragment
  ||| [0,1,2] is affine-safe — every variable used at most once.
  flagship : AffineOk [0, 1, 2]
  ||| Layer 3 (invariant): the composition law applied to the canonical
  ||| disjoint fragments yields an affine-safe sequenced fragment [0,1,2,3].
  invariant : AffineOk ([0, 1] ++ [2, 3])
  ||| Layer 4 (FFI seam): the ABI<->C `Result` encoding is injective, i.e.
  ||| equal wire integers imply equal ABI outcomes (distinct outcomes never
  ||| collide). Carried as the full injectivity theorem.
  seamInjective : (a, b : Result) -> resultToInt a = resultToInt b -> a = b

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-- The capstone value: the whole ABI contract, discharged together
--------------------------------------------------------------------------------

||| THE CAPSTONE. A single inhabited certificate built entirely from the
||| lower-layer exported witnesses:
|||   * `flagship`      = `safeTraceAffineOk` (Layer 2 positive control)
|||   * `invariant`     = `composedOk`        (Layer 3 composition control)
|||   * `seamInjective` = `resultToIntInjective` (Layer 4 seam theorem)
||| Typechecking this value is exactly the end-to-end soundness statement.
public export
abiContractDischarged : ABISound
abiContractDischarged =
  MkABISound safeTraceAffineOk composedOk resultToIntInjective