//! Managed temporary storage use cases.

use std::sync::Arc;

use domain::ports::{Clock, IdGenerator, ManagedTempStore};
use domain::{
    ManagedTempAllocation, ManagedTempGcReport, ManagedTempHandle, ManagedTempKind,
    ManagedTempLease, ProjectId,
};

use crate::error::AppError;

/// Default lease TTL for managed temp allocations: 24 hours.
pub const MANAGED_TEMP_DEFAULT_TTL_MS: u64 = 24 * 60 * 60 * 1_000;
/// Maximum purpose length retained in metadata.
pub const MANAGED_TEMP_PURPOSE_MAX_CHARS: usize = 120;

/// Input for [`AllocateManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct AllocateManagedTempInput {
    /// Optional project that requested this allocation.
    pub owner_project_id: Option<ProjectId>,
    /// Physical allocation kind.
    pub kind: ManagedTempKind,
    /// Short human/debug purpose.
    pub purpose: String,
    /// Optional TTL override in milliseconds. `None` uses the default.
    pub ttl_ms: Option<u64>,
}

/// Output for [`AllocateManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct AllocateManagedTempOutput {
    /// Allocated lease.
    pub lease: ManagedTempLease,
}

/// Allocates an IdeA-managed temporary file/directory.
pub struct AllocateManagedTemp {
    store: Arc<dyn ManagedTempStore>,
    ids: Arc<dyn IdGenerator>,
    clock: Arc<dyn Clock>,
}

impl AllocateManagedTemp {
    /// Builds the use case.
    #[must_use]
    pub fn new(
        store: Arc<dyn ManagedTempStore>,
        ids: Arc<dyn IdGenerator>,
        clock: Arc<dyn Clock>,
    ) -> Self {
        Self { store, ids, clock }
    }

    /// Executes allocation.
    pub async fn execute(
        &self,
        input: AllocateManagedTempInput,
    ) -> Result<AllocateManagedTempOutput, AppError> {
        let purpose = bounded_purpose(input.purpose)?;
        let now = now_ms(&self.clock);
        let ttl_ms = input.ttl_ms.unwrap_or(MANAGED_TEMP_DEFAULT_TTL_MS);
        if ttl_ms == 0 {
            return Err(AppError::Invalid(
                "managed temp ttl must be positive".to_owned(),
            ));
        }
        let expires_at_ms = now.checked_add(ttl_ms).ok_or_else(|| {
            AppError::Invalid("managed temp ttl exceeds timestamp range".to_owned())
        })?;
        let handle = ManagedTempHandle::new(self.ids.new_uuid().to_string())
            .map_err(|err| AppError::Invalid(err.to_string()))?;
        let lease = self
            .store
            .allocate(ManagedTempAllocation {
                handle,
                kind: input.kind,
                owner_project_id: input.owner_project_id,
                purpose,
                created_at_ms: now,
                expires_at_ms: Some(expires_at_ms),
            })
            .await?;
        Ok(AllocateManagedTempOutput { lease })
    }
}

/// Input for [`ResolveManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ResolveManagedTempInput {
    /// Opaque handle to resolve.
    pub handle: String,
}

/// Output for [`ResolveManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ResolveManagedTempOutput {
    /// Resolved active lease.
    pub lease: ManagedTempLease,
}

/// Resolves a managed temp handle.
pub struct ResolveManagedTemp {
    store: Arc<dyn ManagedTempStore>,
    clock: Arc<dyn Clock>,
}

impl ResolveManagedTemp {
    /// Builds the use case.
    #[must_use]
    pub fn new(store: Arc<dyn ManagedTempStore>, clock: Arc<dyn Clock>) -> Self {
        Self { store, clock }
    }

    /// Executes resolution.
    pub async fn execute(
        &self,
        input: ResolveManagedTempInput,
    ) -> Result<ResolveManagedTempOutput, AppError> {
        let handle = ManagedTempHandle::new(input.handle)
            .map_err(|err| AppError::Invalid(err.to_string()))?;
        let lease = self.store.resolve(&handle, now_ms(&self.clock)).await?;
        Ok(ResolveManagedTempOutput { lease })
    }
}

/// Input for [`ReleaseManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ReleaseManagedTempInput {
    /// Opaque handle to release.
    pub handle: String,
}

/// Output for [`ReleaseManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ReleaseManagedTempOutput {
    /// Released lease.
    pub lease: ManagedTempLease,
}

/// Releases a managed temp handle.
pub struct ReleaseManagedTemp {
    store: Arc<dyn ManagedTempStore>,
    clock: Arc<dyn Clock>,
}

impl ReleaseManagedTemp {
    /// Builds the use case.
    #[must_use]
    pub fn new(store: Arc<dyn ManagedTempStore>, clock: Arc<dyn Clock>) -> Self {
        Self { store, clock }
    }

    /// Executes release.
    pub async fn execute(
        &self,
        input: ReleaseManagedTempInput,
    ) -> Result<ReleaseManagedTempOutput, AppError> {
        let handle = ManagedTempHandle::new(input.handle)
            .map_err(|err| AppError::Invalid(err.to_string()))?;
        let lease = self.store.release(&handle, now_ms(&self.clock)).await?;
        Ok(ReleaseManagedTempOutput { lease })
    }
}

/// Output for [`GcManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct GcManagedTempOutput {
    /// GC report.
    pub report: ManagedTempGcReport,
}

/// Runs managed temp garbage collection.
pub struct GcManagedTemp {
    store: Arc<dyn ManagedTempStore>,
    clock: Arc<dyn Clock>,
}

impl GcManagedTemp {
    /// Builds the use case.
    #[must_use]
    pub fn new(store: Arc<dyn ManagedTempStore>, clock: Arc<dyn Clock>) -> Self {
        Self { store, clock }
    }

    /// Executes GC.
    pub async fn execute(&self) -> Result<GcManagedTempOutput, AppError> {
        let report = self.store.gc(now_ms(&self.clock)).await?;
        Ok(GcManagedTempOutput { report })
    }
}

/// Output for [`PurgeManagedTemp`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PurgeManagedTempOutput {
    /// Purge report.
    pub report: ManagedTempGcReport,
}

/// Eagerly purges all managed temporary allocations.
pub struct PurgeManagedTemp {
    store: Arc<dyn ManagedTempStore>,
}

impl PurgeManagedTemp {
    /// Builds the use case.
    #[must_use]
    pub fn new(store: Arc<dyn ManagedTempStore>) -> Self {
        Self { store }
    }

    /// Executes the purge.
    pub async fn execute(&self) -> Result<PurgeManagedTempOutput, AppError> {
        let report = self.store.purge_all().await?;
        Ok(PurgeManagedTempOutput { report })
    }
}

fn now_ms(clock: &Arc<dyn Clock>) -> u64 {
    u64::try_from(clock.now_millis()).unwrap_or(0)
}

fn bounded_purpose(raw: String) -> Result<String, AppError> {
    let trimmed = raw.trim();
    if trimmed.is_empty() {
        return Err(AppError::Invalid(
            "managed temp purpose must not be empty".to_owned(),
        ));
    }
    Ok(trimmed
        .chars()
        .take(MANAGED_TEMP_PURPOSE_MAX_CHARS)
        .collect())
}