//! Chunked Upload Handler - TUS-like Protocol Endpoints
//!
//! Provides HTTP endpoints for resumable, parallel chunk uploads:
//! - POST   /api/uploads          → Create upload session
//! - PATCH  /api/uploads/:id      → Upload a chunk
//! - HEAD   /api/uploads/:id      → Get upload status
//! - POST   /api/uploads/:id/complete → Assemble and finalize
//! - DELETE /api/uploads/:id      → Cancel upload

use axum::{
    Json,
    extract::{Path, Query, State},
    http::{HeaderMap, StatusCode, header},
    response::{IntoResponse, Response},
};
use bytes::Bytes;
use serde::{Deserialize, Serialize};
use std::sync::Arc;

use crate::application::ports::chunked_upload_ports::ChunkedUploadPort;
use crate::application::ports::chunked_upload_ports::DEFAULT_CHUNK_SIZE;
use crate::application::ports::file_ports::FileUploadUseCase;
use crate::application::ports::storage_ports::StorageUsagePort;
use crate::common::di::AppState;
use crate::interfaces::errors::AppError;
use crate::interfaces::middleware::auth::AuthUser;

/// Request body for creating an upload session
#[derive(Debug, Deserialize)]
pub struct CreateUploadRequest {
    pub filename: String,
    pub folder_id: Option<String>,
    pub content_type: Option<String>,
    pub total_size: u64,
    pub chunk_size: Option<usize>,
}

/// Query params for chunk upload
#[derive(Debug, Deserialize)]
pub struct ChunkUploadParams {
    pub chunk_index: usize,
    pub checksum: Option<String>,
}

/// Final response after completing upload
#[derive(Debug, Serialize)]
pub struct CompleteUploadResponse {
    pub file_id: String,
    pub filename: String,
    pub size: u64,
    pub path: String,
}

/// Chunked Upload Handler
pub struct ChunkedUploadHandler;

impl ChunkedUploadHandler {
    /// POST /api/uploads - Create a new upload session
    ///
    /// Request body:
    /// ```json
    /// {
    ///   "filename": "large-video.mp4",
    ///   "folder_id": "optional-folder-id",
    ///   "content_type": "video/mp4",
    ///   "total_size": 104857600,
    ///   "chunk_size": 5242880
    /// }
    /// ```
    ///
    /// Response:
    /// ```json
    /// {
    ///   "upload_id": "uuid",
    ///   "chunk_size": 5242880,
    ///   "total_chunks": 20,
    ///   "expires_at": 86400
    /// }
    /// ```
    pub async fn create_upload(
        State(state): State<Arc<AppState>>,
        auth_user: AuthUser,
        Json(request): Json<CreateUploadRequest>,
    ) -> impl IntoResponse {
        let chunked_service = &state.core.chunked_upload_service;

        // Validate request
        if request.filename.is_empty() {
            return (
                StatusCode::BAD_REQUEST,
                Json(serde_json::json!({
                    "error": "Filename is required"
                })),
            )
                .into_response();
        }

        if request.total_size == 0 {
            return (
                StatusCode::BAD_REQUEST,
                Json(serde_json::json!({
                    "error": "Total size must be greater than 0"
                })),
            )
                .into_response();
        }

        // ── Quota enforcement ────────────────────────────────────
        if let Some(storage_svc) = state.storage_usage_service.as_ref()
            && let Err(err) = storage_svc
                .check_storage_quota(auth_user.id, request.total_size)
                .await
        {
            tracing::warn!(
                "⛔ CHUNKED UPLOAD REJECTED (quota): user={}, file={}, size={} — {}",
                auth_user.username,
                request.filename,
                request.total_size,
                err.message
            );
            return (
                StatusCode::INSUFFICIENT_STORAGE,
                Json(serde_json::json!({
                    "error": err.message,
                    "error_type": "QuotaExceeded"
                })),
            )
                .into_response();
        }

        // Validate chunk size if provided
        let chunk_size = request.chunk_size.unwrap_or(DEFAULT_CHUNK_SIZE);
        if chunk_size < 1024 * 1024 {
            return (
                StatusCode::BAD_REQUEST,
                Json(serde_json::json!({
                    "error": "Chunk size must be at least 1MB"
                })),
            )
                .into_response();
        }

        let content_type = request
            .content_type
            .unwrap_or_else(|| "application/octet-stream".to_string());

        match chunked_service
            .create_session(
                auth_user.id,
                request.filename,
                request.folder_id,
                content_type,
                request.total_size,
                Some(chunk_size),
            )
            .await
        {
            Ok(response) => (StatusCode::CREATED, Json(response)).into_response(),
            Err(e) => {
                tracing::error!("Failed to create upload session: {}", e);
                AppError::internal_error(format!("Failed to create upload session: {}", e))
                    .into_response()
            }
        }
    }

    /// PATCH /api/uploads/:upload_id - Upload a chunk
    ///
    /// Query params:
    /// - chunk_index: The index of the chunk (0-based)
    /// - checksum: Optional MD5 checksum for verification
    ///
    /// Body: Raw bytes of the chunk
    pub async fn upload_chunk(
        State(state): State<Arc<AppState>>,
        auth_user: AuthUser,
        Path(upload_id): Path<String>,
        Query(params): Query<ChunkUploadParams>,
        headers: HeaderMap,
        body: Bytes,
    ) -> impl IntoResponse {
        let chunked_service = &state.core.chunked_upload_service;

        // Extract checksum from header or query param
        let checksum = params.checksum.or_else(|| {
            headers
                .get("Content-MD5")
                .and_then(|v| v.to_str().ok())
                .map(|s| s.to_string())
        });

        match chunked_service
            .upload_chunk(&upload_id, auth_user.id, params.chunk_index, body, checksum)
            .await
        {
            Ok(response) => {
                let mut resp = Response::builder()
                    .status(StatusCode::OK)
                    .header(header::CONTENT_TYPE, "application/json")
                    .header("Upload-Offset", response.bytes_received.to_string())
                    .header(
                        "Upload-Progress",
                        format!("{:.2}", response.progress * 100.0),
                    );

                if response.is_complete {
                    resp = resp.header("Upload-Complete", "true");
                }

                resp.body(axum::body::Body::from(
                    serde_json::to_string(&response).unwrap(),
                ))
                .unwrap()
                .into_response()
            }
            Err(e) => AppError::from(e).into_response(),
        }
    }

    /// HEAD /api/uploads/:upload_id - Get upload status
    ///
    /// Returns upload progress and pending chunks
    pub async fn get_upload_status(
        State(state): State<Arc<AppState>>,
        auth_user: AuthUser,
        Path(upload_id): Path<String>,
    ) -> impl IntoResponse {
        let chunked_service = &state.core.chunked_upload_service;

        match chunked_service.get_status(&upload_id, auth_user.id).await {
            Ok(status) => Response::builder()
                .status(StatusCode::OK)
                .header(header::CONTENT_TYPE, "application/json")
                .header("Upload-Offset", status.bytes_received.to_string())
                .header("Upload-Length", status.total_size.to_string())
                .header("Upload-Progress", format!("{:.2}", status.progress * 100.0))
                .header("Upload-Chunks-Total", status.total_chunks.to_string())
                .header(
                    "Upload-Chunks-Complete",
                    status.completed_chunks.to_string(),
                )
                .body(axum::body::Body::from(
                    serde_json::to_string(&status).unwrap(),
                ))
                .unwrap()
                .into_response(),
            Err(e) => AppError::from(e).into_response(),
        }
    }

    /// POST /api/uploads/:upload_id/complete - Finalize upload
    ///
    /// Assembles all chunks into the final file and creates the file record
    pub async fn complete_upload(
        State(state): State<Arc<AppState>>,
        auth_user: AuthUser,
        Path(upload_id): Path<String>,
    ) -> impl IntoResponse {
        let chunked_service = &state.core.chunked_upload_service;
        let upload_service = &state.applications.file_upload_service;

        // Assemble chunks (hash-on-write: SHA-256 computed during assembly)
        let (assembled_path, filename, folder_id, content_type, total_size, hash) =
            match chunked_service
                .complete_upload(&upload_id, auth_user.id)
                .await
            {
                Ok(result) => result,
                Err(e) => {
                    return AppError::from(e).into_response();
                }
            };

        // ── MIME detection (magic bytes + extension fallback) ─────
        let content_type = crate::common::mime_detect::refine_content_type_from_file(
            &assembled_path,
            &filename,
            &content_type,
        )
        .await;

        // Upload from assembled file on disk — zero extra RAM copies, hash pre-computed
        match upload_service
            .upload_file_from_path(
                filename.clone(),
                folder_id.clone(),
                content_type,
                &assembled_path,
                Some(hash),
            )
            .await
        {
            Ok(file) => {
                // Cleanup session
                let _ = chunked_service
                    .finalize_upload(&upload_id, auth_user.id)
                    .await;

                tracing::info!(
                    "✅ CHUNKED UPLOAD COMPLETE: {} (ID: {}, {} bytes)",
                    filename,
                    file.id,
                    total_size
                );

                (
                    StatusCode::CREATED,
                    Json(CompleteUploadResponse {
                        file_id: file.id,
                        filename: file.name,
                        size: total_size,
                        path: file.path,
                    }),
                )
                    .into_response()
            }
            Err(e) => {
                tracing::error!("Failed to create file from assembled upload: {:?}", e);
                AppError::internal_error(format!("Failed to create file: {}", e)).into_response()
            }
        }
    }

    /// DELETE /api/uploads/:upload_id - Cancel upload
    ///
    /// Cancels an in-progress upload and cleans up temp files
    pub async fn cancel_upload(
        State(state): State<Arc<AppState>>,
        auth_user: AuthUser,
        Path(upload_id): Path<String>,
    ) -> impl IntoResponse {
        let chunked_service = &state.core.chunked_upload_service;

        match chunked_service
            .cancel_upload(&upload_id, auth_user.id)
            .await
        {
            Ok(_) => StatusCode::NO_CONTENT.into_response(),
            Err(e) => {
                AppError::internal_error(format!("Failed to cancel upload: {}", e)).into_response()
            }
        }
    }
}
