package handler

import (
	"context"
	"io"
	"strconv"

	"gcy_hpc_server/internal/model"
	"gcy_hpc_server/internal/server"
	"gcy_hpc_server/internal/service"

	"github.com/gin-gonic/gin"
	"go.uber.org/zap"
)

// uploadServiceProvider defines the interface for upload operations.
type uploadServiceProvider interface {
	InitUpload(ctx context.Context, req model.InitUploadRequest) (interface{}, error)
	UploadChunk(ctx context.Context, sessionID int64, chunkIndex int, reader io.Reader, size int64) error
	CompleteUpload(ctx context.Context, sessionID int64) (*model.FileResponse, error)
	GetUploadStatus(ctx context.Context, sessionID int64) (*model.UploadSessionResponse, error)
	CancelUpload(ctx context.Context, sessionID int64) error
}

// UploadHandler handles HTTP requests for chunked file uploads.
type UploadHandler struct {
	svc    uploadServiceProvider
	logger *zap.Logger
}

// NewUploadHandler creates a new UploadHandler.
func NewUploadHandler(svc *service.UploadService, logger *zap.Logger) *UploadHandler {
	return &UploadHandler{svc: svc, logger: logger}
}

// InitUpload initiates a new chunked upload session.
// POST /api/v1/files/uploads
func (h *UploadHandler) InitUpload(c *gin.Context) {
	var req model.InitUploadRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		h.logger.Warn("invalid request body for init upload", zap.Error(err))
		server.BadRequest(c, err.Error())
		return
	}

	result, err := h.svc.InitUpload(c.Request.Context(), req)
	if err != nil {
		h.logger.Error("failed to init upload", zap.Error(err))
		server.BadRequest(c, err.Error())
		return
	}

	switch resp := result.(type) {
	case model.FileResponse:
		server.OK(c, resp)
	case model.UploadSessionResponse:
		server.Created(c, resp)
	default:
		server.Created(c, resp)
	}
}

// UploadChunk uploads a single chunk of an upload session.
// PUT /api/v1/files/uploads/:id/chunks/:index
func (h *UploadHandler) UploadChunk(c *gin.Context) {
	sessionID, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		h.logger.Warn("invalid session id", zap.String("id", c.Param("id")))
		server.BadRequest(c, "invalid session id")
		return
	}

	chunkIndex, err := strconv.Atoi(c.Param("index"))
	if err != nil {
		h.logger.Warn("invalid chunk index", zap.String("index", c.Param("index")))
		server.BadRequest(c, "invalid chunk index")
		return
	}

	file, header, err := c.Request.FormFile("chunk")
	if err != nil {
		h.logger.Warn("missing chunk file in request", zap.Error(err))
		server.BadRequest(c, "missing chunk file")
		return
	}
	defer file.Close()

	if err := h.svc.UploadChunk(c.Request.Context(), sessionID, chunkIndex, file, header.Size); err != nil {
		h.logger.Error("failed to upload chunk", zap.Int64("session_id", sessionID), zap.Int("chunk_index", chunkIndex), zap.Error(err))
		server.BadRequest(c, err.Error())
		return
	}

	server.OK(c, gin.H{"message": "chunk uploaded"})
}

// CompleteUpload finalizes an upload session and assembles the file.
// POST /api/v1/files/uploads/:id/complete
func (h *UploadHandler) CompleteUpload(c *gin.Context) {
	sessionID, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		h.logger.Warn("invalid session id for complete", zap.String("id", c.Param("id")))
		server.BadRequest(c, "invalid session id")
		return
	}

	resp, err := h.svc.CompleteUpload(c.Request.Context(), sessionID)
	if err != nil {
		h.logger.Error("failed to complete upload", zap.Int64("session_id", sessionID), zap.Error(err))
		server.InternalError(c, err.Error())
		return
	}

	server.Created(c, resp)
}

// GetUploadStatus returns the current status of an upload session.
// GET /api/v1/files/uploads/:id
func (h *UploadHandler) GetUploadStatus(c *gin.Context) {
	sessionID, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		h.logger.Warn("invalid session id for status", zap.String("id", c.Param("id")))
		server.BadRequest(c, "invalid session id")
		return
	}

	resp, err := h.svc.GetUploadStatus(c.Request.Context(), sessionID)
	if err != nil {
		h.logger.Error("failed to get upload status", zap.Int64("session_id", sessionID), zap.Error(err))
		server.InternalError(c, err.Error())
		return
	}

	server.OK(c, resp)
}

// CancelUpload cancels and cleans up an upload session.
// DELETE /api/v1/files/uploads/:id
func (h *UploadHandler) CancelUpload(c *gin.Context) {
	sessionID, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		h.logger.Warn("invalid session id for cancel", zap.String("id", c.Param("id")))
		server.BadRequest(c, "invalid session id")
		return
	}

	if err := h.svc.CancelUpload(c.Request.Context(), sessionID); err != nil {
		h.logger.Error("failed to cancel upload", zap.Int64("session_id", sessionID), zap.Error(err))
		server.InternalError(c, err.Error())
		return
	}

	server.OK(c, gin.H{"message": "upload cancelled"})
}