use std::collections::HashMap;
use std::collections::HashSet;
use std::path::PathBuf;
use std::sync::Arc;
use std::sync::Mutex;
use std::sync::MutexGuard;
use std::sync::OnceLock;

use chrono::Utc;
use codex_protocol::ThreadId;
use codex_protocol::models::PermissionProfile;
use codex_protocol::protocol::AskForApproval;
use codex_protocol::protocol::RolloutItem;
use codex_protocol::protocol::SessionContextWindow;
use codex_protocol::protocol::SessionMeta;
use codex_protocol::protocol::SessionMetaLine;
use codex_protocol::protocol::ThreadMemoryMode;
use codex_rollout::persisted_rollout_items;

use crate::AppendThreadItemsParams;
use crate::ArchiveThreadParams;
use crate::CreateThreadParams;
use crate::DeleteThreadParams;
use crate::ListThreadsParams;
use crate::LoadThreadHistoryParams;
use crate::ReadThreadByRolloutPathParams;
use crate::ReadThreadParams;
use crate::ResumeThreadParams;
use crate::StoredThread;
use crate::StoredThreadHistory;
use crate::ThreadMetadataPatch;
use crate::ThreadPage;
use crate::ThreadRelationFilter;
use crate::ThreadStore;
use crate::ThreadStoreError;
use crate::ThreadStoreFuture;
use crate::ThreadStoreResult;
use crate::UpdateThreadMetadataParams;

static IN_MEMORY_THREAD_STORES: OnceLock<Mutex<HashMap<String, Arc<InMemoryThreadStore>>>> =
    OnceLock::new();

fn stores() -> &'static Mutex<HashMap<String, Arc<InMemoryThreadStore>>> {
    IN_MEMORY_THREAD_STORES.get_or_init(|| Mutex::new(HashMap::new()))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::ListItemsParams;
    use crate::ListTurnsParams;
    use crate::SortDirection;
    use crate::StoredTurnItemsView;
    use crate::ThreadPersistenceMetadata;
    use crate::ThreadSortKey;
    use codex_protocol::models::BaseInstructions;
    use codex_protocol::protocol::SessionSource;

    #[tokio::test]
    async fn default_turn_pagination_methods_return_unsupported() {
        let store = InMemoryThreadStore::default();
        let thread_id = ThreadId::default();

        let turns_err = store
            .list_turns(ListTurnsParams {
                thread_id,
                include_archived: true,
                cursor: None,
                page_size: 10,
                sort_direction: SortDirection::Asc,
                items_view: StoredTurnItemsView::Summary,
            })
            .await
            .expect_err("default list_turns should be unsupported");
        assert!(matches!(
            turns_err,
            ThreadStoreError::Unsupported {
                operation: "list_turns"
            }
        ));

        let items_err = store
            .list_items(ListItemsParams {
                thread_id,
                turn_id: None,
                include_archived: true,
                cursor: None,
                page_size: 10,
                sort_direction: SortDirection::Asc,
            })
            .await
            .expect_err("default list_items should be unsupported");
        assert!(matches!(
            items_err,
            ThreadStoreError::Unsupported {
                operation: "list_items"
            }
        ));
    }

    #[tokio::test]
    async fn list_threads_filters_by_spawn_relationship() {
        let store = InMemoryThreadStore::default();
        let parent_thread_id = ThreadId::default();
        let child_thread_id =
            ThreadId::from_string("00000000-0000-0000-0000-000000000001").expect("valid thread id");
        let unrelated_thread_id =
            ThreadId::from_string("00000000-0000-0000-0000-000000000002").expect("valid thread id");
        let grandchild_thread_id =
            ThreadId::from_string("00000000-0000-0000-0000-000000000003").expect("valid thread id");

        for (thread_id, parent_thread_id) in [
            (child_thread_id, Some(parent_thread_id)),
            (unrelated_thread_id, None),
            (grandchild_thread_id, Some(child_thread_id)),
        ] {
            store
                .create_thread(CreateThreadParams {
                    session_id: thread_id.into(),
                    thread_id,
                    extra_config: None,
                    forked_from_id: None,
                    parent_thread_id,
                    source: SessionSource::Exec,
                    thread_source: None,
                    originator: "test_originator".to_string(),
                    base_instructions: BaseInstructions::default(),
                    dynamic_tools: Vec::new(),
                    selected_capability_roots: Vec::new(),
                    multi_agent_version: None,
                    initial_window_id: uuid::Uuid::now_v7().to_string(),
                    metadata: ThreadPersistenceMetadata {
                        cwd: None,
                        model_provider: "test-provider".to_string(),
                        memory_mode: ThreadMemoryMode::Enabled,
                    },
                })
                .await
                .expect("create thread");
        }

        let page = ThreadStore::list_threads(
            &store,
            ListThreadsParams {
                page_size: 10,
                cursor: None,
                sort_key: ThreadSortKey::CreatedAt,
                sort_direction: SortDirection::Desc,
                allowed_sources: Vec::new(),
                model_providers: None,
                cwd_filters: None,
                archived: false,
                search_term: None,
                relation_filter: Some(ThreadRelationFilter::DirectChildrenOf(parent_thread_id)),
                use_state_db_only: false,
            },
        )
        .await
        .expect("list child threads");

        assert_eq!(
            page.items
                .into_iter()
                .map(|item| item.thread_id)
                .collect::<Vec<_>>(),
            vec![child_thread_id]
        );

        let page = ThreadStore::list_threads(
            &store,
            ListThreadsParams {
                page_size: 10,
                cursor: None,
                sort_key: ThreadSortKey::CreatedAt,
                sort_direction: SortDirection::Desc,
                allowed_sources: Vec::new(),
                model_providers: None,
                cwd_filters: None,
                archived: false,
                search_term: None,
                relation_filter: Some(ThreadRelationFilter::DescendantsOf(parent_thread_id)),
                use_state_db_only: false,
            },
        )
        .await
        .expect("list descendant threads");

        assert_eq!(
            page.items
                .into_iter()
                .map(|item| item.thread_id)
                .collect::<HashSet<_>>(),
            HashSet::from([child_thread_id, grandchild_thread_id])
        );
    }
}

fn stores_guard() -> MutexGuard<'static, HashMap<String, Arc<InMemoryThreadStore>>> {
    match stores().lock() {
        Ok(guard) => guard,
        Err(poisoned) => poisoned.into_inner(),
    }
}

/// Recorded call counts for [`InMemoryThreadStore`].
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct InMemoryThreadStoreCalls {
    pub create_thread: usize,
    pub resume_thread: usize,
    pub append_items: usize,
    pub persist_thread: usize,
    pub flush_thread: usize,
    pub shutdown_thread: usize,
    pub discard_thread: usize,
    pub load_history: usize,
    pub read_thread: usize,
    pub read_thread_with_history: usize,
    pub read_thread_by_rollout_path: usize,
    pub list_threads: usize,
    pub update_thread_metadata: usize,
    pub archive_thread: usize,
    pub unarchive_thread: usize,
    pub delete_thread: usize,
}

/// In-memory [`ThreadStore`] implementation for tests and debug configs.
///
/// Test and debug configs can select this store by id, letting tests exercise
/// config-driven non-local persistence without requiring the real remote gRPC
/// service.
#[derive(Default)]
pub struct InMemoryThreadStore {
    state: tokio::sync::Mutex<InMemoryThreadStoreState>,
}

#[derive(Default)]
struct InMemoryThreadStoreState {
    calls: InMemoryThreadStoreCalls,
    created_threads: HashMap<ThreadId, CreateThreadParams>,
    histories: HashMap<ThreadId, Vec<RolloutItem>>,
    metadata_updates: HashMap<ThreadId, ThreadMetadataPatch>,
    names: HashMap<ThreadId, Option<String>>,
    rollout_paths: HashMap<PathBuf, ThreadId>,
}

impl InMemoryThreadStore {
    /// Returns the store associated with `id`, creating it if needed.
    pub fn for_id(id: impl Into<String>) -> Arc<Self> {
        let id = id.into();
        let mut stores = stores_guard();
        stores
            .entry(id)
            .or_insert_with(|| Arc::new(Self::default()))
            .clone()
    }

    /// Removes a shared in-memory store for `id`.
    pub fn remove_id(id: &str) -> Option<Arc<Self>> {
        stores_guard().remove(id)
    }

    /// Returns the calls observed by this store.
    pub async fn calls(&self) -> InMemoryThreadStoreCalls {
        self.state.lock().await.calls.clone()
    }

    async fn create_thread(&self, params: CreateThreadParams) -> ThreadStoreResult<()> {
        let mut state = self.state.lock().await;
        state.calls.create_thread += 1;
        let session_meta = SessionMeta {
            session_id: params.session_id,
            id: params.thread_id,
            forked_from_id: params.forked_from_id,
            parent_thread_id: params.parent_thread_id,
            cwd: params.metadata.cwd.clone().unwrap_or_default(),
            agent_nickname: params.source.get_nickname(),
            agent_role: params.source.get_agent_role(),
            agent_path: params.source.get_agent_path().map(Into::into),
            originator: params.originator.clone(),
            source: params.source.clone(),
            thread_source: params.thread_source.clone(),
            model_provider: Some(params.metadata.model_provider.clone()),
            base_instructions: Some(params.base_instructions.clone()),
            dynamic_tools: (!params.dynamic_tools.is_empty()).then(|| params.dynamic_tools.clone()),
            selected_capability_roots: params.selected_capability_roots.clone(),
            memory_mode: matches!(params.metadata.memory_mode, ThreadMemoryMode::Disabled)
                .then_some("disabled".to_string()),
            multi_agent_version: params.multi_agent_version,
            context_window: Some(SessionContextWindow::new(params.initial_window_id.clone())),
            ..SessionMeta::default()
        };
        state
            .histories
            .entry(params.thread_id)
            .or_default()
            .push(RolloutItem::SessionMeta(SessionMetaLine {
                meta: session_meta,
                git: None,
            }));
        state.created_threads.insert(params.thread_id, params);
        Ok(())
    }

    async fn resume_thread(&self, params: ResumeThreadParams) -> ThreadStoreResult<()> {
        let mut state = self.state.lock().await;
        state.calls.resume_thread += 1;
        if let Some(history) = params.history {
            state
                .histories
                .insert(params.thread_id, Arc::unwrap_or_clone(history));
        } else {
            state.histories.entry(params.thread_id).or_default();
        }
        if let Some(rollout_path) = params.rollout_path {
            state.rollout_paths.insert(rollout_path, params.thread_id);
        }
        Ok(())
    }

    async fn append_items(&self, params: AppendThreadItemsParams) -> ThreadStoreResult<()> {
        let canonical_items = persisted_rollout_items(params.items.as_slice());
        if canonical_items.is_empty() {
            return Ok(());
        }
        let mut state = self.state.lock().await;
        state.calls.append_items += 1;
        state
            .histories
            .entry(params.thread_id)
            .or_default()
            .extend(canonical_items);
        Ok(())
    }

    async fn load_history(
        &self,
        params: LoadThreadHistoryParams,
    ) -> ThreadStoreResult<StoredThreadHistory> {
        let mut state = self.state.lock().await;
        state.calls.load_history += 1;
        let items = state.histories.get(&params.thread_id).cloned().ok_or(
            ThreadStoreError::ThreadNotFound {
                thread_id: params.thread_id,
            },
        )?;
        Ok(StoredThreadHistory {
            thread_id: params.thread_id,
            items,
        })
    }

    async fn read_thread(&self, params: ReadThreadParams) -> ThreadStoreResult<StoredThread> {
        let mut state = self.state.lock().await;
        state.calls.read_thread += 1;
        if params.include_history {
            state.calls.read_thread_with_history += 1;
        }
        stored_thread_from_state(&state, params.thread_id, params.include_history)
    }

    async fn read_thread_by_rollout_path(
        &self,
        params: ReadThreadByRolloutPathParams,
    ) -> ThreadStoreResult<StoredThread> {
        let mut state = self.state.lock().await;
        state.calls.read_thread_by_rollout_path += 1;
        let Some(thread_id) = state.rollout_paths.get(&params.rollout_path).copied() else {
            return Err(ThreadStoreError::InvalidRequest {
                message: format!(
                    "in-memory thread store does not know rollout path {}",
                    params.rollout_path.display()
                ),
            });
        };
        stored_thread_from_state(&state, thread_id, params.include_history)
    }

    async fn list_threads(&self) -> ThreadStoreResult<ThreadPage> {
        let mut state = self.state.lock().await;
        state.calls.list_threads += 1;
        let mut items = state
            .created_threads
            .keys()
            .map(|thread_id| {
                stored_thread_from_state(&state, *thread_id, /*include_history*/ false)
            })
            .collect::<ThreadStoreResult<Vec<_>>>()?;
        items.sort_by_key(|item| item.thread_id.to_string());
        Ok(ThreadPage {
            items,
            next_cursor: None,
        })
    }

    async fn update_thread_metadata(
        &self,
        params: UpdateThreadMetadataParams,
    ) -> ThreadStoreResult<StoredThread> {
        let mut state = self.state.lock().await;
        state.calls.update_thread_metadata += 1;
        if let Some(name) = params.patch.name.clone() {
            state.names.insert(params.thread_id, name);
        }
        state
            .metadata_updates
            .entry(params.thread_id)
            .or_default()
            .merge(params.patch);
        stored_thread_from_state(&state, params.thread_id, /*include_history*/ false)
    }

    async fn delete_thread(&self, params: DeleteThreadParams) -> ThreadStoreResult<()> {
        let mut state = self.state.lock().await;
        state.calls.delete_thread += 1;
        let existed = state.histories.remove(&params.thread_id).is_some();
        state.created_threads.remove(&params.thread_id);
        state.names.remove(&params.thread_id);
        state.metadata_updates.remove(&params.thread_id);
        state
            .rollout_paths
            .retain(|_, thread_id| *thread_id != params.thread_id);
        if existed {
            Ok(())
        } else {
            Err(ThreadStoreError::ThreadNotFound {
                thread_id: params.thread_id,
            })
        }
    }
}

impl ThreadStore for InMemoryThreadStore {
    fn as_any(&self) -> &dyn std::any::Any {
        self
    }

    fn create_thread(&self, params: CreateThreadParams) -> ThreadStoreFuture<'_, ()> {
        Box::pin(InMemoryThreadStore::create_thread(self, params))
    }

    fn resume_thread(&self, params: ResumeThreadParams) -> ThreadStoreFuture<'_, ()> {
        Box::pin(InMemoryThreadStore::resume_thread(self, params))
    }

    fn append_items(&self, params: AppendThreadItemsParams) -> ThreadStoreFuture<'_, ()> {
        Box::pin(InMemoryThreadStore::append_items(self, params))
    }

    fn persist_thread(&self, _thread_id: ThreadId) -> ThreadStoreFuture<'_, ()> {
        Box::pin(async move {
            self.state.lock().await.calls.persist_thread += 1;
            Ok(())
        })
    }

    fn flush_thread(&self, _thread_id: ThreadId) -> ThreadStoreFuture<'_, ()> {
        Box::pin(async move {
            self.state.lock().await.calls.flush_thread += 1;
            Ok(())
        })
    }

    fn shutdown_thread(&self, _thread_id: ThreadId) -> ThreadStoreFuture<'_, ()> {
        Box::pin(async move {
            self.state.lock().await.calls.shutdown_thread += 1;
            Ok(())
        })
    }

    fn discard_thread(&self, _thread_id: ThreadId) -> ThreadStoreFuture<'_, ()> {
        Box::pin(async move {
            self.state.lock().await.calls.discard_thread += 1;
            Ok(())
        })
    }

    fn load_history(
        &self,
        params: LoadThreadHistoryParams,
    ) -> ThreadStoreFuture<'_, StoredThreadHistory> {
        Box::pin(InMemoryThreadStore::load_history(self, params))
    }

    fn read_thread(&self, params: ReadThreadParams) -> ThreadStoreFuture<'_, StoredThread> {
        Box::pin(InMemoryThreadStore::read_thread(self, params))
    }

    fn read_thread_by_rollout_path(
        &self,
        params: ReadThreadByRolloutPathParams,
    ) -> ThreadStoreFuture<'_, StoredThread> {
        Box::pin(InMemoryThreadStore::read_thread_by_rollout_path(
            self, params,
        ))
    }

    fn list_threads(&self, params: ListThreadsParams) -> ThreadStoreFuture<'_, ThreadPage> {
        Box::pin(async move {
            let mut page = InMemoryThreadStore::list_threads(self).await?;
            match params.relation_filter {
                Some(ThreadRelationFilter::DirectChildrenOf(parent_thread_id)) => {
                    page.items
                        .retain(|thread| thread.parent_thread_id == Some(parent_thread_id));
                }
                Some(ThreadRelationFilter::DescendantsOf(ancestor_thread_id)) => {
                    let mut subtree = HashSet::from([ancestor_thread_id]);
                    loop {
                        let mut discovered = false;
                        for thread in &page.items {
                            if thread
                                .parent_thread_id
                                .is_some_and(|parent_thread_id| subtree.contains(&parent_thread_id))
                            {
                                discovered |= subtree.insert(thread.thread_id);
                            }
                        }
                        if !discovered {
                            break;
                        }
                    }
                    page.items.retain(|thread| {
                        thread.thread_id != ancestor_thread_id
                            && subtree.contains(&thread.thread_id)
                    });
                }
                None => {}
            }
            Ok(page)
        })
    }

    fn update_thread_metadata(
        &self,
        params: UpdateThreadMetadataParams,
    ) -> ThreadStoreFuture<'_, StoredThread> {
        Box::pin(InMemoryThreadStore::update_thread_metadata(self, params))
    }

    fn archive_thread(&self, _params: ArchiveThreadParams) -> ThreadStoreFuture<'_, ()> {
        Box::pin(async move {
            self.state.lock().await.calls.archive_thread += 1;
            Ok(())
        })
    }

    fn unarchive_thread(&self, params: ArchiveThreadParams) -> ThreadStoreFuture<'_, StoredThread> {
        Box::pin(async move {
            let mut state = self.state.lock().await;
            state.calls.unarchive_thread += 1;
            stored_thread_from_state(&state, params.thread_id, /*include_history*/ false)
        })
    }

    fn delete_thread(&self, params: DeleteThreadParams) -> ThreadStoreFuture<'_, ()> {
        Box::pin(InMemoryThreadStore::delete_thread(self, params))
    }
}

fn stored_thread_from_state(
    state: &InMemoryThreadStoreState,
    thread_id: ThreadId,
    include_history: bool,
) -> ThreadStoreResult<StoredThread> {
    let created = state
        .created_threads
        .get(&thread_id)
        .ok_or(ThreadStoreError::ThreadNotFound { thread_id })?;
    let history_items = state.histories.get(&thread_id).cloned().unwrap_or_default();
    let history = include_history.then(|| StoredThreadHistory {
        thread_id,
        items: history_items.clone(),
    });
    let name = state.names.get(&thread_id).cloned().flatten();
    let metadata = state.metadata_updates.get(&thread_id);
    let rollout_path = state
        .rollout_paths
        .iter()
        .find_map(|(path, mapped_thread_id)| {
            (*mapped_thread_id == thread_id).then(|| path.clone())
        });

    Ok(StoredThread {
        thread_id,
        extra_config: created.extra_config.clone(),
        rollout_path: metadata
            .and_then(|metadata| metadata.rollout_path.clone())
            .or(rollout_path),
        forked_from_id: created.forked_from_id,
        parent_thread_id: created.parent_thread_id,
        preview: metadata
            .and_then(|metadata| metadata.preview.clone())
            .unwrap_or_default(),
        name,
        model_provider: metadata
            .and_then(|metadata| metadata.model_provider.clone())
            .unwrap_or_else(|| "test".to_string()),
        model: metadata.and_then(|metadata| metadata.model.clone()),
        reasoning_effort: metadata.and_then(|metadata| metadata.reasoning_effort.clone()),
        created_at: metadata
            .and_then(|metadata| metadata.created_at)
            .unwrap_or_else(Utc::now),
        updated_at: metadata
            .and_then(|metadata| metadata.updated_at)
            .unwrap_or_else(Utc::now),
        recency_at: metadata
            .and_then(|metadata| metadata.advance_recency_at.or(metadata.updated_at))
            .unwrap_or_else(Utc::now),
        archived_at: None,
        cwd: metadata
            .and_then(|metadata| metadata.cwd.clone())
            .unwrap_or_default(),
        cli_version: metadata
            .and_then(|metadata| metadata.cli_version.clone())
            .unwrap_or_else(|| "test".to_string()),
        source: metadata
            .and_then(|metadata| metadata.source.clone())
            .unwrap_or_else(|| created.source.clone()),
        thread_source: metadata
            .and_then(|metadata| metadata.thread_source.clone())
            .unwrap_or_else(|| created.thread_source.clone()),
        agent_nickname: metadata.and_then(|metadata| metadata.agent_nickname.clone().flatten()),
        agent_role: metadata.and_then(|metadata| metadata.agent_role.clone().flatten()),
        agent_path: metadata.and_then(|metadata| metadata.agent_path.clone().flatten()),
        git_info: metadata.and_then(git_info_from_patch),
        approval_mode: metadata
            .and_then(|metadata| metadata.approval_mode)
            .unwrap_or(AskForApproval::Never),
        permission_profile: metadata
            .and_then(|metadata| metadata.permission_profile.clone())
            .unwrap_or_else(PermissionProfile::read_only),
        token_usage: metadata.and_then(|metadata| metadata.token_usage.clone()),
        first_user_message: metadata.and_then(|metadata| metadata.first_user_message.clone()),
        history,
    })
}

fn git_info_from_patch(patch: &ThreadMetadataPatch) -> Option<codex_protocol::protocol::GitInfo> {
    let git_info = patch.git_info.as_ref()?;
    let sha = git_info.sha.clone().flatten();
    let branch = git_info.branch.clone().flatten();
    let origin_url = git_info.origin_url.clone().flatten();
    if sha.is_none() && branch.is_none() && origin_url.is_none() {
        return None;
    }
    Some(codex_protocol::protocol::GitInfo {
        commit_hash: sha.as_deref().map(codex_git_utils::GitSha::new),
        branch,
        repository_url: origin_url,
    })
}