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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

//! Support for mocking the Diem data store.

use crate::account::AccountData;
use anyhow::Result;
use diem_state_view::StateView;
use diem_types::{
    access_path::AccessPath,
    on_chain_config::ConfigStorage,
    transaction::ChangeSet,
    write_set::{WriteOp, WriteSet},
};
use diem_vm::data_cache::RemoteStorage;
use move_binary_format::errors::*;
use move_core_types::{
    account_address::AccountAddress,
    language_storage::{ModuleId, StructTag},
    resolver::{ModuleResolver, ResourceResolver},
};
use once_cell::sync::Lazy;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use vm_genesis::{generate_genesis_change_set_for_testing, GenesisOptions};

/// Dummy genesis ChangeSet for testing
pub static GENESIS_CHANGE_SET: Lazy<ChangeSet> =
    Lazy::new(|| generate_genesis_change_set_for_testing(GenesisOptions::Compiled));

pub static GENESIS_CHANGE_SET_FRESH: Lazy<ChangeSet> =
    Lazy::new(|| generate_genesis_change_set_for_testing(GenesisOptions::Fresh));

/// An in-memory implementation of [`StateView`] and [`RemoteCache`] for the VM.
///
/// Tests use this to set up state, and pass in a reference to the cache whenever a `StateView` or
/// `RemoteCache` is needed.
#[derive(Debug, Default, Clone, Serialize, Deserialize)]
pub struct FakeDataStore {
    data: HashMap<AccessPath, Vec<u8>>,
}

impl FakeDataStore {
    /// Creates a new `FakeDataStore` with the provided initial data.
    pub fn new(data: HashMap<AccessPath, Vec<u8>>) -> Self {
        FakeDataStore { data }
    }

    /// Adds a [`WriteSet`] to this data store.
    pub fn add_write_set(&mut self, write_set: &WriteSet) {
        for (access_path, write_op) in write_set {
            match write_op {
                WriteOp::Value(blob) => {
                    self.set(access_path.clone(), blob.clone());
                }
                WriteOp::Deletion => {
                    self.remove(access_path);
                }
            }
        }
    }

    /// Sets a (key, value) pair within this data store.
    ///
    /// Returns the previous data if the key was occupied.
    pub fn set(&mut self, access_path: AccessPath, data_blob: Vec<u8>) -> Option<Vec<u8>> {
        self.data.insert(access_path, data_blob)
    }

    /// Deletes a key from this data store.
    ///
    /// Returns the previous data if the key was occupied.
    pub fn remove(&mut self, access_path: &AccessPath) -> Option<Vec<u8>> {
        self.data.remove(access_path)
    }

    /// Adds an [`AccountData`] to this data store.
    pub fn add_account_data(&mut self, account_data: &AccountData) {
        let write_set = account_data.to_writeset();
        self.add_write_set(&write_set)
    }

    /// Adds a [`CompiledModule`] to this data store.
    ///
    /// Does not do any sort of verification on the module.
    pub fn add_module(&mut self, module_id: &ModuleId, blob: Vec<u8>) {
        let access_path = AccessPath::from(module_id);
        self.set(access_path, blob);
    }

    /// Yields a reference to the internal data structure of the global state
    pub fn inner(&self) -> &HashMap<AccessPath, Vec<u8>> {
        &self.data
    }
}

impl ConfigStorage for FakeDataStore {
    fn fetch_config(&self, access_path: AccessPath) -> Option<Vec<u8>> {
        StateView::get(self, &access_path).unwrap_or_default()
    }
}

// This is used by the `execute_block` API.
// TODO: only the "sync" get is implemented
impl StateView for FakeDataStore {
    fn get(&self, access_path: &AccessPath) -> Result<Option<Vec<u8>>> {
        // Since the data is in-memory, it can't fail.
        Ok(self.data.get(access_path).cloned())
    }

    fn is_genesis(&self) -> bool {
        self.data.is_empty()
    }
}

impl ModuleResolver for FakeDataStore {
    type Error = VMError;

    fn get_module(&self, module_id: &ModuleId) -> Result<Option<Vec<u8>>, Self::Error> {
        RemoteStorage::new(self).get_module(module_id)
    }
}

impl ResourceResolver for FakeDataStore {
    type Error = VMError;

    fn get_resource(
        &self,
        address: &AccountAddress,
        tag: &StructTag,
    ) -> Result<Option<Vec<u8>>, Self::Error> {
        RemoteStorage::new(self).get_resource(address, tag)
    }
}