From 4e7dd4e0b4cd8dcb5342d8caaa57db033b7d1fba Mon Sep 17 00:00:00 2001
From: Sosthene <contact@sosthene.net>
Date: Tue, 12 Nov 2024 23:22:20 +0100
Subject: [PATCH] Refactor states update

---
 src/process.rs | 91 ++++++++++++++++++++++++++------------------------
 1 file changed, 47 insertions(+), 44 deletions(-)

diff --git a/src/process.rs b/src/process.rs
index ac83ac6..a70763f 100644
--- a/src/process.rs
+++ b/src/process.rs
@@ -174,28 +174,46 @@ impl Process {
         Ok(last_state.commited_in)
     }
 
-    /// We want to always keep an empty state with only the latest unspent commited_in value at the last position
-    pub fn insert_state(&mut self, prd_update: &Prd) -> anyhow::Result<()> {
-        if prd_update.prd_type != PrdType::Update { return Err(anyhow::Error::msg("Only update prd allowed")) }
+    pub fn update_states_tip(&mut self, new_commitment: OutPoint) -> anyhow::Result<()> {
         if self.states.is_empty() { return Err(anyhow::Error::msg("Empty Process")); }
-        let new_encrypted_pcd: Value = serde_json::from_str(&prd_update.payload).unwrap();
-        let last_index = self.states.len() - 1;
-        let last_value = self.states.get(last_index).unwrap();
-        if last_value.encrypted_pcd != Value::Null || 
-            last_value.keys != Map::new() ||
-            last_value.pcd_commitment != Value::Null ||
-            last_value.validation_tokens != vec![]
-        {
-            return Err(anyhow::Error::msg("Last state is not empty"));
+        let last_value = self.states.last().unwrap();
+        if !last_value.is_empty() {
+            return Err(anyhow::Error::msg("Last value should be empty"));
         }
-        let empty_state = self.states.remove(last_index);
-        let new_state = ProcessState {
-            commited_in: empty_state.commited_in,
-            pcd_commitment: prd_update.pcd_commitments.clone(),
-            encrypted_pcd: new_encrypted_pcd,
-            keys: prd_update.keys.clone(),
-            validation_tokens: vec![]
+        if last_value.commited_in == new_commitment {
+            return Err(anyhow::Error::msg("new_commitment is the same than existing tip"));
+        }
+
+        // Before updating we make sure that we only have one concurrent state
+        let concurrent_states = self.get_latest_concurrent_states()?;
+        if concurrent_states.len() != 2 {
+            return Err(anyhow::Error::msg("We must have exactly one state for the current tip"));
+        }
+
+        // Replace the existing tip
+        let new_tip = ProcessState {
+            commited_in: new_commitment,
+            ..Default::default()
         };
+        let _ = self.states.pop().unwrap();
+        self.states.push(new_tip);
+
+        Ok(())
+    }
+
+    /// We want to insert a new state that would be commited by the last UTXO
+    /// The new state *must* have the same commited_in than the last empty one
+    /// We want to always keep an empty state with only the latest unspent commited_in value at the last position
+    pub fn insert_concurrent_state(&mut self, new_state: ProcessState) -> anyhow::Result<()> {
+        if self.states.is_empty() { return Err(anyhow::Error::msg("Empty Process")); }
+        let last_value = self.states.last().unwrap();
+        if !last_value.is_empty() {
+            return Err(anyhow::Error::msg("Last value should be empty"));
+        }
+        if last_value.commited_in != new_state.commited_in {
+            return Err(anyhow::Error::msg("A concurrent state must have the same commited in than the tip of the states"));
+        }
+        let empty_state = self.states.pop().unwrap();
         self.states.push(new_state);
         // We always keep an empty state at the end
         self.states.push(empty_state);
@@ -281,36 +299,22 @@ impl Process {
         Ok(states)
     }
 
-    pub fn remove_latest_concurrent_states(&mut self) -> anyhow::Result<Vec<ProcessState>> {
+    pub fn remove_all_concurrent_states(&mut self) -> anyhow::Result<Vec<ProcessState>> {
         if self.get_number_of_states() == 0 {
             // This should never happen, but we better get rid of it now
             return Err(anyhow::Error::msg("process is empty".to_owned()));
         }
 
-        let mut previous_commited_in = OutPoint::null();
-        // Iterate backwards, find the reverse position, and adjust to forward position
-        let reverse_position = self.states.iter().rev().position(|state| {
-            if previous_commited_in == OutPoint::null() {
-                previous_commited_in = state.commited_in;
-                false // Continue iterating
-            } else if previous_commited_in != state.commited_in {
-                true // Stop when a different commited_in is found
-            } else {
-                false // Continue iterating
-            }
-        });
+        let empty_state = self.states.pop().unwrap();
+        let last_commitment_outpoint = empty_state.commited_in;
+        let split_index = self.states.iter().position(|state| state.commited_in == last_commitment_outpoint).unwrap();
 
-        let forward_position = reverse_position.map(|pos| self.states.len() - pos - 1);
+        let removed = self.states.split_off(split_index);
 
-        match forward_position {
-            Some(pos) => Ok(self.states.split_off(pos)),
-            None => {
-                // We take everything out
-                let res = self.states.to_vec();
-                self.states = vec![];
-                Ok(res)
-            }
-        }
+        // We make sure we always have an empty state at the end
+        self.states.push(empty_state);
+
+        Ok(removed)
     }
 
     pub fn get_latest_commited_state(&self) -> Option<&ProcessState> {
@@ -379,8 +383,7 @@ mod tests {
 
     use serde_json::json;
     use sp_client::{
-        bitcoin::{secp256k1::SecretKey, Network},
-        spclient::{SpClient, SpWallet, SpendKey},
+        bitcoin::{secp256k1::SecretKey, Network}, silentpayments::utils::SilentPaymentAddress, spclient::{SpClient, SpWallet, SpendKey}
     };
 
     use crate::pcd::{Member, ValidationRule};