/- Copyright (c) 2026 Sovereign Research Stack. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Research Stack Team

ENEDistributedNode.lean — ENE Distributed Node Gossip Protocol & Consensus

Replaces infra/ene_distributed_node.py gossip protocol and consensus logic with a formal Lean module.
Defines gossip message structure, consensus voting, and node identity.

Per AGENTS.md:
  - Q16_16 for scoring (§1.4)
  - PascalCase types, camelCase functions (§2)
  - Theorems for correctness (§4)
  - No proof placeholders in committed code (§1.6)
-/

import Mathlib.Data.Nat.Basic
import Mathlib.Data.List.Basic
import Std

namespace Semantics.ENEDistributedNode

-- ═══════════════════════════════════════════════════════════════════════════
-- §0  Q16_16 Fixed-Point Arithmetic
-- ═══════════════════════════════════════════════════════════════════════════

structure Q16_16 where
  raw : Int
  deriving Repr, DecidableEq, Inhabited

namespace Q16_16
  def zero : Q16_16 := ⟨0⟩
  def one : Q16_16 := ⟨65536⟩
  def ofFrac (num denom : Nat) : Q16_16 :=
    if denom = 0 then zero else ⟨(num * 65536) / denom⟩
end Q16_16

-- ═══════════════════════════════════════════════════════════════════════════
-- §1  Gossip Message Type Enumeration
-- ═══════════════════════════════════════════════════════════════════════════

inductive GossipMessageType where
  | discovery : GossipMessageType
  | heartbeat : GossipMessageType
  | credentialSync : GossipMessageType
  | replicate : GossipMessageType
  | credentialRotationProposal : GossipMessageType
  deriving Repr, DecidableEq, Inhabited

-- ═══════════════════════════════════════════════════════════════════════════
-- ═══════════════════════════════════════════════════════════════════════════
-- §2  Node Identity Structure
-- ═══════════════════════════════════════════════════════════════════════════

structure NodeIdentity where
  nodeId : String
  publicKey : String
  ipAddress : Option String
  port : Nat
  firstSeen : Nat
  lastSeen : Nat
  replicationVersion : String
  capabilities : List String
  healthScore : Q16_16
  isActive : Bool
  deriving Repr, Inhabited

/-- Initialize node identity -/
def initNodeIdentity (nodeId publicKey : String) (port : Nat) (currentTime : Nat) : NodeIdentity :=
  {
    nodeId := nodeId,
    publicKey := publicKey,
    ipAddress := none,
    port := port,
    firstSeen := currentTime,
    lastSeen := currentTime,
    replicationVersion := "2.0.0-Cambrian-Bind",
    capabilities := ["storage", "compute", "relay"],
    healthScore := Q16_16.one,
    isActive := true
  }

-- ═══════════════════════════════════════════════════════════════════════════
-- ═══════════════════════════════════════════════════════════════════════════
-- §3  Gossip Message Structure
-- ═══════════════════════════════════════════════════════════════════════════

structure GossipMessage where
  messageId : String
  senderNode : String
  messageType : GossipMessageType
  payload : String  -- JSON-encoded payload
  timestamp : Nat
  ttl : Nat  -- Time-to-live hops
  signature : Option String
  deriving Repr, Inhabited

/-- Create gossip message -/
def createGossipMessage (senderNode : String) (messageType : GossipMessageType) 
    (payload : String) (timestamp : Nat) : GossipMessage :=
  {
    messageId := s!"gossip_{timestamp}",
    senderNode := senderNode,
    messageType := messageType,
    payload := payload,
    timestamp := timestamp,
    ttl := 10,
    signature := none
  }

-- ═══════════════════════════════════════════════════════════════════════════
-- ═══════════════════════════════════════════════════════════════════════════
-- §4  Consensus Voting
-- ═══════════════════════════════════════════════════════════════════════════

structure ConsensusVote where
  proposalId : String
  voterId : String
  approve : Bool
  timestamp : Nat
  deriving Repr, Inhabited

structure ConsensusState where
  proposalId : String
  credentialId : String
  proposer : String
  votes : List ConsensusVote
  totalNodes : Nat
  createdAt : Nat
  deriving Repr, Inhabited

/-- Initialize consensus state -/
def initConsensusState (proposalId credentialId proposer : String) (totalNodes : Nat) (currentTime : Nat) : ConsensusState :=
  {
    proposalId := proposalId,
    credentialId := credentialId,
    proposer := proposer,
    votes := [],
    totalNodes := totalNodes,
    createdAt := currentTime
  }

/-- Add vote to consensus state -/
def addVote (state : ConsensusState) (vote : ConsensusVote) : ConsensusState :=
  { state with votes := vote :: state.votes }

/-- Check if consensus is reached (2/3 majority) -/
def isConsensusReached (state : ConsensusState) : Bool :=
  let approveCount := state.votes.foldl (fun acc (v : ConsensusVote) => 
    if v.approve then acc + 1 else acc
  ) 0
  let required := (state.totalNodes * 2) / 3
  approveCount ≥ required

-- ═══════════════════════════════════════════════════════════════════════════
-- ═════════════════════════════════════════════════════════════════════════════
-- §5  Mesh Health
-- ═══════════════════════════════════════════════════════════════════════════

structure MeshHealth where
  meshSize : Nat
  healthyNodes : Nat
  replicatedNodes : Nat
  gossipBacklog : Nat
  meshStatus : String
  deriving Repr, Inhabited

/-- Calculate mesh health from node identities -/
def calculateMeshHealth (nodes : List NodeIdentity) (replicatedNodes gossipBacklog : Nat) : MeshHealth :=
  let healthyNodes := nodes.foldl (fun acc (n : NodeIdentity) =>
    if n.healthScore.raw ≥ 32768 then acc + 1 else acc  -- health > 0.5
  ) 0
  let meshSize := nodes.length
  let meshStatus := if healthyNodes ≥ meshSize / 2 then "healthy" else "degraded"
  
  {
    meshSize := meshSize,
    healthyNodes := healthyNodes,
    replicatedNodes := replicatedNodes,
    gossipBacklog := gossipBacklog,
    meshStatus := meshStatus
  }

-- ═══════════════════════════════════════════════════════════════════════════
-- §6  Theorems
-- ═══════════════════════════════════════════════════════════════════════════

/-- Initial node identity has full health score -/
theorem initNodeIdentityFullHealth (nodeId publicKey : String) (port currentTime : Nat) :
    (initNodeIdentity nodeId publicKey port currentTime).healthScore = Q16_16.one := by
  rfl

/-- Empty consensus state has no votes -/
theorem emptyConsensusHasNoVotes (proposalId credentialId proposer : String) (totalNodes currentTime : Nat) :
    (initConsensusState proposalId credentialId proposer totalNodes currentTime).votes.length = 0 := by
  rfl

-- ═══════════════════════════════════════════════════════════════════════════
-- ═══════════════════════════════════════════════════════════════════════════
-- §7  Example Usage
-- ═══════════════════════════════════════════════════════════════════════════

#eval let identity := initNodeIdentity "node_001" "pubkey_abc123" 7947 1000
      identity.healthScore

#eval let msg := createGossipMessage "node_001" GossipMessageType.discovery "{\"node_id\":\"node_002\"}" 1000
      msg.messageType

#eval let state := initConsensusState "prop_001" "cred_001" "node_001" 3 1000
      let vote1 := { proposalId := "prop_001", voterId := "node_001", approve := true, timestamp := 1000 }
      let vote2 := { proposalId := "prop_001", voterId := "node_002", approve := true, timestamp := 1000 }
      let state2 := addVote state vote1
      let state3 := addVote state2 vote2
      isConsensusReached state3

#eval let node1 := initNodeIdentity "node_001" "pubkey1" 7947 1000
      let node2 := initNodeIdentity "node_002" "pubkey2" 7947 1000
      let health := calculateMeshHealth [node1, node2] 1 0
      health.meshStatus

end Semantics.ENEDistributedNode
