//! Use cases for ephemeral AI ticket editing assistants.

use std::sync::Arc;

use domain::ports::{AgentSessionFactory, SessionPlan};
use domain::AgentProfile;
use domain::{
    AgentToolPolicy, AgentToolPolicyStore, AssistantContextProvider, DomainEvent, EventBus,
    IssueRef, IssueStore, ProfileId, ProfileStore, Project, SessionId,
};

use crate::terminal::StructuredSessions;
use crate::AppError;

/// Opens an ephemeral ticket assistant chat session.
pub struct OpenTicketAssistant {
    issues: Arc<dyn IssueStore>,
    profiles: Arc<dyn ProfileStore>,
    contexts: Arc<dyn AssistantContextProvider>,
    factory: Arc<dyn AgentSessionFactory>,
    structured: Arc<StructuredSessions>,
    policies: Arc<dyn AgentToolPolicyStore>,
    events: Arc<dyn EventBus>,
}

/// Input for [`OpenTicketAssistant`].
pub struct OpenTicketAssistantInput {
    /// Project owning the ticket.
    pub project: Project,
    /// Ticket reference to bind.
    pub issue_ref: IssueRef,
    /// Structured profile to use.
    pub profile_id: ProfileId,
}

/// Output of [`OpenTicketAssistant`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct OpenTicketAssistantOutput {
    /// Live structured session id, to be driven by `agent_send`.
    pub session_id: SessionId,
    /// MCP requester identity bound to this assistant.
    pub requester: String,
    /// Bound ticket reference.
    pub issue_ref: IssueRef,
}

impl OpenTicketAssistant {
    /// Builds the use case.
    #[allow(clippy::too_many_arguments)]
    #[must_use]
    pub fn new(
        issues: Arc<dyn IssueStore>,
        profiles: Arc<dyn ProfileStore>,
        contexts: Arc<dyn AssistantContextProvider>,
        factory: Arc<dyn AgentSessionFactory>,
        structured: Arc<StructuredSessions>,
        policies: Arc<dyn AgentToolPolicyStore>,
        events: Arc<dyn EventBus>,
    ) -> Self {
        Self {
            issues,
            profiles,
            contexts,
            factory,
            structured,
            policies,
            events,
        }
    }

    /// Executes the open flow.
    ///
    /// Reopening an already-live assistant for the same ticket replaces the old
    /// session after the fresh one has started. This guarantees the assistant sees
    /// the latest ticket content/profile and keeps the invariant "one assistant per
    /// ticket" without leaving a gap if the new launch fails.
    pub async fn execute(
        &self,
        input: OpenTicketAssistantInput,
    ) -> Result<OpenTicketAssistantOutput, AppError> {
        let issue = self
            .issues
            .get_by_ref(&input.project.root, input.issue_ref)
            .await?;
        let profile = find_profile(&self.profiles, input.profile_id).await?;
        if !self.factory.supports(&profile) {
            return Err(AppError::Invalid(format!(
                "profile {} cannot start a structured ticket assistant",
                input.profile_id
            )));
        }
        let prepared = self
            .contexts
            .prepare_ticket_assistant_context(&input.project, &issue)
            .await
            .map_err(|e| AppError::Store(e.to_string()))?;
        let session = self
            .factory
            .start(
                &profile,
                &prepared,
                &input.project.root,
                &SessionPlan::None,
                &[],
                None,
            )
            .await
            .map_err(AppError::from)?;
        let session_id = session.id();
        let requester = session_id.to_string();
        let policy = AgentToolPolicy::new(
            vec![
                "idea_ticket_read".to_owned(),
                "idea_ticket_update".to_owned(),
                "idea_ticket_update_carnet".to_owned(),
            ],
            Some(input.issue_ref),
            true,
        );

        if let Some(old_requester) = self.structured.ticket_assistant_requester(input.issue_ref) {
            self.policies.clear_policy(&old_requester);
        }
        let replaced = self.structured.insert_ticket_assistant(
            input.issue_ref,
            requester.clone(),
            Arc::clone(&session),
        );
        self.policies.set_policy(requester.clone(), policy);
        if let Some(old) = replaced {
            let _ = old.shutdown().await;
        }
        self.events.publish(DomainEvent::TicketAssistantOpened {
            issue_ref: input.issue_ref,
            profile_id: input.profile_id,
        });

        Ok(OpenTicketAssistantOutput {
            session_id,
            requester,
            issue_ref: input.issue_ref,
        })
    }
}

/// Closes an ephemeral ticket assistant chat session.
pub struct CloseTicketAssistant {
    structured: Arc<StructuredSessions>,
    policies: Arc<dyn AgentToolPolicyStore>,
    events: Arc<dyn EventBus>,
}

/// Input for [`CloseTicketAssistant`].
pub struct CloseTicketAssistantInput {
    /// Ticket reference whose assistant should be closed.
    pub issue_ref: IssueRef,
}

impl CloseTicketAssistant {
    /// Builds the use case.
    #[must_use]
    pub fn new(
        structured: Arc<StructuredSessions>,
        policies: Arc<dyn AgentToolPolicyStore>,
        events: Arc<dyn EventBus>,
    ) -> Self {
        Self {
            structured,
            policies,
            events,
        }
    }

    /// Executes the close flow.
    pub async fn execute(&self, input: CloseTicketAssistantInput) -> Result<(), AppError> {
        let (session, requester) = self
            .structured
            .remove_ticket_assistant(input.issue_ref)
            .ok_or_else(|| AppError::NotFound(format!("ticket assistant {}", input.issue_ref)))?;
        self.policies.clear_policy(&requester);
        session.shutdown().await.map_err(AppError::from)?;
        self.events.publish(DomainEvent::TicketAssistantClosed {
            issue_ref: input.issue_ref,
        });
        Ok(())
    }
}

async fn find_profile(
    profiles: &Arc<dyn ProfileStore>,
    profile_id: ProfileId,
) -> Result<AgentProfile, AppError> {
    profiles
        .list()
        .await?
        .into_iter()
        .find(|profile| profile.id == profile_id)
        .ok_or_else(|| AppError::NotFound(format!("profile {profile_id}")))
}