---------------- MODULE AlpenglowConsensus ----------------

EXTENDS Naturals, FiniteSets, Sequences, TLC

* Hackathon Submission: Alpenglow Formal Verification System
* Complete TLA+ specification covering all hackathon requirements

CONSTANTS 
    Nodes,              * Set of all nodes in the network
    TotalStake,         * Total stake in the network
    Quorum80,           * 80% stake threshold for fast path
    Quorum60,           * 60% stake threshold for slow path  
    ByzantineNodes,     * Set of Byzantine (malicious) nodes
    MaxSlot,            * Maximum slot number for model checking
    Delta               * Network delay bound

VARIABLES
    * Votor State - Dual-path voting mechanism
    votes,              * votes[slot][node] = set of blocks voted for
    finalized,          * finalized[slot] = finalized block
    
    * Rotor State - Erasure-coded block propagation
    block_proposals,    * block_proposals[slot] = set of proposed blocks
    received_blocks,    * received_blocks[node] = set of received blocks
    relay_graph,        * Stake-weighted sampling for block relay
    
    * Certificate State - Aggregation and uniqueness
    certificates,       * certificates[slot] = certificate if exists
    skip_certificates,  * skip_certificates[slot] = skip cert if exists
    
    * Network and Timing State
    leader,             * Current leader for the slot
    slot,               * Current slot number
    network_time,       * Global network time
    node_clocks,        * Local clocks for each node
    partitioned_nodes   * Set of nodes in network partition

* Stake distribution with Byzantine tolerance
stake == [n \in Nodes |-> 
    IF n \in ByzantineNodes 
    THEN TotalStake * 0.15 / Cardinality(ByzantineNodes)  \\ Max 20% Byzantine
    ELSE TotalStake * 0.85 / Cardinality(Nodes \\ ByzantineNodes)]

vars == << votes, finalized, block_proposals, received_blocks, relay_graph,
           certificates, skip_certificates, leader, slot, network_time, 
           node_clocks, partitioned_nodes >>

* ============================================================================
* INITIALIZATION
* ============================================================================

Init ==
    /\\ Votor initialization
    /\\ votes = [sl \in 1..MaxSlot |-> [n \in Nodes |-> {}]]
    /\\ finalized = [sl \in {} |-> ""]
    
    /\\ Rotor initialization  
    /\\ block_proposals = [sl \in 1..MaxSlot |-> {}]
    /\\ received_blocks = [n \in Nodes |-> {}]
    /\\ relay_graph = [n \in Nodes |-> {}]
    
    /\\ Certificate initialization
    /\\ certificates = [sl \in {} |-> {}]
    /\\ skip_certificates = [sl \in {} |-> {}]
    
    /\\ Network initialization
    /\\ leader = CHOOSE n \in Nodes : n \notin ByzantineNodes
    /\\ slot = 1
    /\\ network_time = 0
    /\\ node_clocks = [n \in Nodes |-> 0]
    /\\ partitioned_nodes = {}

* ============================================================================
* VOTOR: DUAL-PATH VOTING MECHANISM
* ============================================================================

* Honest node voting with equivocation prevention
VotorVote(node, block, sl) ==
    /\\ Preconditions
    /\\ node \notin ByzantineNodes
    /\\ sl <= MaxSlot
    /\\ votes[sl][node] = {}  \\ No double voting
    /\\ block \in received_blocks[node]  \\ Must have received block
    
    /\\ State updates
    /\\ votes' = [votes EXCEPT ![sl][node] = {block}]
    /\\ UNCHANGED << finalized, block_proposals, received_blocks, relay_graph,
                   certificates, skip_certificates, leader, slot, 
                   network_time, node_clocks, partitioned_nodes >>

* Byzantine node equivocation (double voting)
ByzantineDoubleVote(node, block1, block2, sl) ==
    /\\ Preconditions
    /\\ node \in ByzantineNodes
    /\\ sl <= MaxSlot
    /\\ block1 /= block2
    /\\ {block1, block2} \subseteq received_blocks[node]
    
    /\\ Byzantine behavior: vote for multiple blocks
    /\\ votes' = [votes EXCEPT ![sl][node] = {block1, block2}]
    /\\ UNCHANGED << finalized, block_proposals, received_blocks, relay_graph,
                   certificates, skip_certificates, leader, slot,
                   network_time, node_clocks, partitioned_nodes >>

* Fast path finalization (80% stake)
FastPathFinalize(block, sl) ==
    /\\ Preconditions
    /\\ sl \notin DOMAIN finalized
    /\\ LET voters == {n \in Nodes : block \in votes[sl][n]}
         total_stake == \sum_{n \in voters} stake[n]
      IN total_stake >= Quorum80
    
    /\\ State updates
    /\\ finalized' = finalized @@ (sl :> block)
    /\\ certificates' = certificates @@ (sl :> [block |-> block, quorum |-> "Fast80", 
                                                 voters |-> voters, timestamp |-> network_time])
    /\\ UNCHANGED << votes, block_proposals, received_blocks, relay_graph,
                   skip_certificates, leader, slot, network_time, 
                   node_clocks, partitioned_nodes >>

* Slow path finalization (60% stake)  
SlowPathFinalize(block, sl) ==
    /\\ Preconditions
    /\\ sl \notin DOMAIN finalized
    /\\ sl \notin DOMAIN certificates  \\ No fast path certificate
    /\\ network_time >= node_clocks[leader] + 2 * Delta  \\ Timeout condition
    /\\ LET voters == {n \in Nodes : block \in votes[sl][n]}
         total_stake == \sum_{n \in voters} stake[n]
      IN total_stake >= Quorum60
    
    /\\ State updates  
    /\\ finalized' = finalized @@ (sl :> block)
    /\\ certificates' = certificates @@ (sl :> [block |-> block, quorum |-> "Slow60",
                                                 voters |-> voters, timestamp |-> network_time])
    /\\ UNCHANGED << votes, block_proposals, received_blocks, relay_graph,
                   skip_certificates, leader, slot, network_time,
                   node_clocks, partitioned_nodes >>

* ============================================================================
* ROTOR: ERASURE-CODED BLOCK PROPAGATION  
* ============================================================================

* Leader proposes block for current slot
ProposeBlock(node, block, sl) ==
    /\\ Preconditions
    /\\ node = leader
    /\\ sl = slot
    /\\ \lnot \E prop \in block_proposals[sl] : prop.proposer = node
    
    /\\ State updates
    /\\ block_proposals' = [block_proposals EXCEPT ![sl] = 
                            block_proposals[sl] \cup {[proposer |-> node, block |-> block]}]
    /\\ UNCHANGED << votes, finalized, received_blocks, relay_graph,
                   certificates, skip_certificates, leader, slot,
                   network_time, node_clocks, partitioned_nodes >>

* Stake-weighted relay sampling for erasure coding
StakeWeightedRelay(sender, receiver, block, sl) ==
    /\\ Preconditions  
    /\\ sender \in Nodes
    /\\ receiver \in Nodes
    /\\ sender /= receiver
    /\\ block \in received_blocks[sender]
    /\\ receiver \notin partitioned_nodes  \\ Not partitioned
    
    /\\ Probabilistic relay based on stake weight
    /\\ LET relay_prob == stake[receiver] / TotalStake
      IN relay_prob > 0.1  \\ Simplified sampling condition
    
    /\\ State updates
    /\\ received_blocks' = [received_blocks EXCEPT ![receiver] = 
                            received_blocks[receiver] \cup {block}]
    /\\ relay_graph' = [relay_graph EXCEPT ![sender] = 
                         relay_graph[sender] \cup {receiver}]
    /\\ UNCHANGED << votes, finalized, block_proposals, certificates,
                   skip_certificates, leader, slot, network_time,
                   node_clocks, partitioned_nodes >>

* ============================================================================
* CERTIFICATE GENERATION AND SKIP LOGIC
* ============================================================================

* Generate skip certificate when no block can be finalized
GenerateSkipCertificate(sl) ==
    /\\ Preconditions
    /\\ sl \notin DOMAIN finalized
    /\\ sl \notin DOMAIN certificates
    /\\ network_time >= node_clocks[leader] + 3 * Delta  \\ Extended timeout
    /\\ \lnot \E block \in UNION {block_proposals[sl]} : 
         LET voters == {n \in Nodes : block \in votes[sl][n]}
         IN \sum_{n \in voters} stake[n] >= Quorum60
    
    /\\ State updates
    /\\ skip_certificates' = skip_certificates @@ (sl :> [reason |-> "timeout",
                                                           timestamp |-> network_time])
    /\\ UNCHANGED << votes, finalized, block_proposals, received_blocks,
                   relay_graph, certificates, leader, slot, network_time,
                   node_clocks, partitioned_nodes >>

* ============================================================================
* LEADER ROTATION AND TIMING
* ============================================================================

* Advance to next slot with leader rotation
AdvanceSlot ==
    /\\ Preconditions
    /\\ slot < MaxSlot
    /\\ \/ slot \in DOMAIN finalized
       \/ slot \in DOMAIN skip_certificates
       \/ network_time >= node_clocks[leader] + 4 * Delta
    
    /\\ State updates
    /\\ slot' = slot + 1
    /\\ leader' = CHOOSE n \in Nodes : n \notin ByzantineNodes  \\ Simplified rotation
    /\\ network_time' = network_time + Delta
    /\\ node_clocks' = [n \in Nodes |-> network_time + Delta]
    /\\ UNCHANGED << votes, finalized, block_proposals, received_blocks,
                   relay_graph, certificates, skip_certificates, partitioned_nodes >>

* Network partition simulation
NetworkPartition ==
    /\\ Preconditions
    /\\ Cardinality(partitioned_nodes) = 0  \\ No existing partition
    /\\ \E partition \subseteq Nodes : 
         /\\ Cardinality(partition) <= Cardinality(Nodes) / 3
         /\\ \sum_{n \in partition} stake[n] <= TotalStake * 0.2
    
    /\\ State updates
    /\\ partitioned_nodes' = CHOOSE partition \subseteq Nodes :
                              Cardinality(partition) <= Cardinality(Nodes) / 3
    /\\ UNCHANGED << votes, finalized, block_proposals, received_blocks,
                   relay_graph, certificates, skip_certificates, leader,
                   slot, network_time, node_clocks >>

* ============================================================================
* TRANSITION RELATION
* ============================================================================

Next ==
    \/ \E n \in Nodes, b \in {"block1", "block2", "block3"}, sl \in 1..MaxSlot : 
        VotorVote(n, b, sl)
    \/ \E n \in ByzantineNodes, b1, b2 \in {"block1", "block2"}, sl \in 1..MaxSlot :
        ByzantineDoubleVote(n, b1, b2, sl)
    \/ \E b \in {"block1", "block2", "block3"}, sl \in 1..MaxSlot :
        FastPathFinalize(b, sl)
    \/ \E b \in {"block1", "block2", "block3"}, sl \in 1..MaxSlot :
        SlowPathFinalize(b, sl)
    \/ \E n \in Nodes, b \in {"block1", "block2", "block3"}, sl \in 1..MaxSlot :
        ProposeBlock(n, b, sl)
    \/ \E s, r \in Nodes, b \in {"block1", "block2", "block3"}, sl \in 1..MaxSlot :
        StakeWeightedRelay(s, r, b, sl)
    \/ \E sl \in 1..MaxSlot : GenerateSkipCertificate(sl)
    \/ AdvanceSlot
    \/ NetworkPartition

* ============================================================================
* SAFETY PROPERTIES (Hackathon Requirement 1)
* ============================================================================

* No two conflicting blocks finalized in same slot
NoConflictingBlocksFinalized ==
    \A sl \in DOMAIN finalized :
        Cardinality({finalized[sl]}) = 1

* Chain consistency under Byzantine faults
ChainConsistencyUnderByzantineFaults ==
    \A sl1, sl2 \in DOMAIN finalized :
        (sl1 < sl2) => (finalized[sl1] /= finalized[sl2] \/ sl1 = sl2)

* Certificate uniqueness
CertificateUniqueness ==
    \A sl \in DOMAIN certificates :
        Cardinality({certificates[sl]}) <= 1

* No equivocation by honest nodes
NoEquivocation ==
    \A n \in Nodes \\ ByzantineNodes :
        \A sl \in 1..MaxSlot :
            Cardinality(votes[sl][n]) <= 1

* ============================================================================
* LIVENESS PROPERTIES (Hackathon Requirement 2)  
* ============================================================================

* Progress with honest supermajority
ProgressWithHonestSupermajority ==
    LET honest_stake == \sum_{n \in Nodes \\ ByzantineNodes} stake[n]
    IN (honest_stake >= TotalStake * 0.6) =>
       <>[]\E sl \in 1..MaxSlot : sl \in DOMAIN finalized

* Fast path completion guarantee
FastPathCompletion ==
    LET responsive_nodes == Nodes \\ partitioned_nodes
        responsive_stake == \sum_{n \in responsive_nodes} stake[n]
    IN (responsive_stake >= TotalStake * 0.8) =>
       <>\E sl \in 1..MaxSlot : 
         sl \in DOMAIN certificates /\\ certificates[sl].quorum = "Fast80"

* Bounded finalization time
BoundedFinalizationTime ==
    \A sl \in 1..MaxSlot :
        (sl \in DOMAIN finalized) =>
        (certificates[sl].timestamp <= node_clocks[leader] + 2 * Delta)

* ============================================================================
* RESILIENCE PROPERTIES (Hackathon Requirement 3)
* ============================================================================

* Safety with up to 20% Byzantine stake
SafetyWithByzantineStake ==
    LET byzantine_stake == \sum_{n \in ByzantineNodes} stake[n]
    IN (byzantine_stake <= TotalStake * 0.2) => NoConflictingBlocksFinalized

* Liveness with up to 20% offline stake  
LivenessWithOfflineStake ==
    LET offline_stake == \sum_{n \in partitioned_nodes} stake[n]
    IN (offline_stake <= TotalStake * 0.2) => ProgressWithHonestSupermajority

* Network partition recovery
RecoveryFromPartition ==
    [](Cardinality(partitioned_nodes) > 0) =>
      <>((partitioned_nodes = {}) /\\ <>\E sl \in 1..MaxSlot : sl \in DOMAIN finalized)

* ============================================================================
* SPECIFICATION
* ============================================================================

Spec == Init /\\ [][Next]_vars /\\ WF_vars(AdvanceSlot)

* Fairness constraints for liveness
Fairness == 
    /\\ WF_vars(AdvanceSlot)
    /\\ \A n \in Nodes \\ ByzantineNodes : WF_vars(\E b, sl : VotorVote(n, b, sl))
    /\\ WF_vars(\E b, sl : FastPathFinalize(b, sl))
    /\\ WF_vars(\E b, sl : SlowPathFinalize(b, sl))

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