package documents

import (
	"bufio"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"mime"
	"mime/multipart"
	"net/http"
	"strings"
	"time"

	"github.com/google/uuid"

	"project/internal/api"
	"project/internal/auth"
)

type Handler struct {
	svc *Service
}

func NewHandler(svc *Service) *Handler {
	return &Handler{svc: svc}
}

// ListDocTypes godoc
//
//	@Summary		List tipe dokumen yang didukung
//	@Tags			documents
//	@Produce		json
//	@Success		200	{object}	api.APIResponse{data=[]DocTypeInfo}
//	@Security		BearerAuth
//	@Router			/api/v1/documents/doctypes [get]
func (h *Handler) ListDocTypes(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, api.APIResponse{
		Status:  "success",
		Message: "supported document types",
		Data:    h.svc.ListDocTypes(),
	})
}

// ListByUser godoc
//
//	@Summary		List dokumen milik user
//	@Tags			documents
//	@Produce		json
//	@Param			user_id	path		string	true	"User ID"
//	@Success		200		{object}	api.APIResponse{data=[]Document}
//	@Failure		500		{object}	api.APIResponse
//	@Security		BearerAuth
//	@Router			/api/v1/documents/{user_id} [get]
func (h *Handler) ListByUser(w http.ResponseWriter, r *http.Request) {
	userID := r.PathValue("user_id")
	if rejectUserMismatch(w, r, userID) {
		return
	}
	docs, err := h.svc.ListByUser(r.Context(), userID)
	if err != nil {
		slog.Error("list documents", "user_id", userID, "err", err)
		writeJSON(w, http.StatusInternalServerError, api.APIResponse{Status: "error", Message: "internal server error"})
		return
	}
	writeJSON(w, http.StatusOK, api.APIResponse{Status: "success", Message: "documents", Data: docs})
}

// Upload godoc
//
//	@Summary		Upload dokumen ke private object storage
//	@Description	Mendukung pdf, docx, txt, csv, xlsx. Maksimum 10 MB. Stream ke private object storage tanpa mengubah kontrak upload frontend.
//	@Tags			documents
//	@Accept			multipart/form-data
//	@Produce		json
//	@Param			user_id	formData	string	true	"User ID"
//	@Param			file	formData	file	true	"File dokumen"
//	@Success		201		{object}	api.APIResponse{data=Document}
//	@Failure		400		{object}	api.APIResponse
//	@Failure		500		{object}	api.APIResponse
//	@Security		BearerAuth
//	@Router			/api/v1/document/upload [post]
func (h *Handler) Upload(w http.ResponseWriter, r *http.Request) {
	reqStart := time.Now()
	requestID := r.Header.Get("X-Request-Id")
	if requestID == "" {
		requestID = uuid.New().String()
	}
	slog.Info("upload: request received",
		"request_id", requestID,
		"remote_addr", r.RemoteAddr,
		"content_length", r.ContentLength,
		"user_agent", r.UserAgent(),
	)

	// r.MultipartReader() uses Go's default 4 KB socket read buffer, causing
	// ~675 syscalls for a 2.7 MB file. On Windows each syscall hits the TCP
	// delayed-ACK timer (~26 ms), adding up to ~17 s. Wrapping r.Body with a
	// 1 MB bufio.Reader reduces that to ~3 syscalls.
	mediaType, params, parseErr := mime.ParseMediaType(r.Header.Get("Content-Type"))
	if parseErr != nil || mediaType != "multipart/form-data" || params["boundary"] == "" {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "multipart/form-data required"})
		return
	}
	mr := multipart.NewReader(bufio.NewReaderSize(r.Body, 1*1024*1024), params["boundary"])

	var userID string
	var filename string
	var fileSize int64
	var filePart io.Reader

	for {
		part, err := mr.NextPart()
		if err == io.EOF {
			break
		}
		if err != nil {
			writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "failed to parse form"})
			return
		}

		switch part.FormName() {
		case "user_id":
			data, _ := io.ReadAll(io.LimitReader(part, 512))
			userID = strings.TrimSpace(string(data))
		case "file":
			filename = part.FileName()
			fileSize = r.ContentLength
			filePart = part
		}

		if userID != "" && filePart != nil {
			break
		}
	}

	if userID == "" {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "user_id is required"})
		return
	}
	if rejectUserMismatch(w, r, userID) {
		return
	}
	if filePart == nil {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "file is required"})
		return
	}

	slog.Info("upload: multipart parsed",
		"request_id", requestID,
		"user_id", userID,
		"filename", filename,
		"content_length", fileSize,
		"elapsed_ms", time.Since(reqStart).Milliseconds(),
	)

	doc, err := h.svc.Upload(r.Context(), userID, filename, filePart, fileSize, requestID)
	if err != nil {
		elapsed := time.Since(reqStart).Milliseconds()
		switch {
		case errors.Is(err, ErrUnsupportedType):
			slog.Warn("upload: unsupported file type", "request_id", requestID, "filename", filename, "elapsed_ms", elapsed)
			writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "unsupported file type"})
		case errors.Is(err, ErrFileTooLarge):
			slog.Warn("upload: file too large", "request_id", requestID, "filename", filename, "elapsed_ms", elapsed)
			writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "file too large (max 10 MB)"})
		default:
			slog.Error("upload: failed", "request_id", requestID, "err", err, "elapsed_ms", elapsed)
			writeJSON(w, http.StatusInternalServerError, api.APIResponse{Status: "error", Message: "upload failed"})
		}
		return
	}
	slog.Info("upload: completed",
		"request_id", requestID,
		"doc_id", doc.ID,
		"user_id", userID,
		"filename", filename,
		"file_size_bytes", doc.FileSize,
		"elapsed_ms", time.Since(reqStart).Milliseconds(),
	)
	writeJSON(w, http.StatusCreated, api.APIResponse{Status: "success", Message: "file uploaded", Data: doc})
}

// UploadLocal godoc
//
//	@Summary		Upload dokumen ke local filesystem (benchmarking)
//	@Description	Sama seperti /upload tetapi menyimpan file ke folder files/ lokal. Digunakan untuk membandingkan performa vs private object storage.
//	@Tags			documents
//	@Accept			multipart/form-data
//	@Produce		json
//	@Param			user_id	formData	string	true	"User ID"
//	@Param			file	formData	file	true	"File dokumen"
//	@Success		201		{object}	api.APIResponse
//	@Failure		400		{object}	api.APIResponse
//	@Failure		500		{object}	api.APIResponse
//	@Security		BearerAuth
//	@Router			/api/v1/document/upload-local [post]
func (h *Handler) UploadLocal(w http.ResponseWriter, r *http.Request) {
	mediaType, params, parseErr := mime.ParseMediaType(r.Header.Get("Content-Type"))
	if parseErr != nil || mediaType != "multipart/form-data" || params["boundary"] == "" {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "multipart/form-data required"})
		return
	}
	mr := multipart.NewReader(bufio.NewReaderSize(r.Body, 1*1024*1024), params["boundary"])

	var userID string
	var filename string
	var fileSize int64
	var filePart io.Reader

	for {
		part, err := mr.NextPart()
		if err == io.EOF {
			break
		}
		if err != nil {
			writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "failed to parse form"})
			return
		}

		switch part.FormName() {
		case "user_id":
			data, _ := io.ReadAll(io.LimitReader(part, 512))
			userID = strings.TrimSpace(string(data))
		case "file":
			filename = part.FileName()
			fileSize = r.ContentLength
			filePart = part
		}

		if userID != "" && filePart != nil {
			break
		}
	}

	if userID == "" {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "user_id is required"})
		return
	}
	if rejectUserMismatch(w, r, userID) {
		return
	}
	if filePart == nil {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "file is required"})
		return
	}

	destPath, err := h.svc.UploadLocal(r.Context(), userID, filename, filePart, fileSize)
	if err != nil {
		switch {
		case errors.Is(err, ErrUnsupportedType):
			writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "unsupported file type"})
		case errors.Is(err, ErrFileTooLarge):
			writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "file too large (max 10 MB)"})
		default:
			slog.Error("local upload failed", "err", err)
			writeJSON(w, http.StatusInternalServerError, api.APIResponse{Status: "error", Message: "local upload failed"})
		}
		return
	}
	writeJSON(w, http.StatusCreated, api.APIResponse{Status: "success", Message: "file saved locally", Data: map[string]string{"path": destPath}})
}

// Process godoc
//
//	@Summary		Proses dokumen secara async (extract text / convert ke Parquet)
//	@Description	Processing berjalan di background. Response 202 dikembalikan segera setelah validasi. Pantau progress via GET /api/v1/documents/{user_id}.
//	@Tags			documents
//	@Accept			json
//	@Produce		json
//	@Param			body	body		object{document_id=string,user_id=string}	true	"Document ID dan User ID"
//	@Success		202		{object}	api.APIResponse{data=ProcessResult}
//	@Failure		400		{object}	api.APIResponse
//	@Failure		403		{object}	api.APIResponse
//	@Failure		404		{object}	api.APIResponse
//	@Failure		500		{object}	api.APIResponse
//	@Security		BearerAuth
//	@Router			/api/v1/document/process [post]
func (h *Handler) Process(w http.ResponseWriter, r *http.Request) {
	var req struct {
		DocumentID string `json:"document_id"`
		UserID     string `json:"user_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "invalid request body"})
		return
	}
	if req.DocumentID == "" || req.UserID == "" {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "document_id and user_id are required"})
		return
	}
	if rejectUserMismatch(w, r, req.UserID) {
		return
	}

	result, err := h.svc.Process(r.Context(), req.DocumentID, req.UserID)
	if err != nil {
		switch {
		case errors.Is(err, ErrNotFound):
			writeJSON(w, http.StatusNotFound, api.APIResponse{Status: "error", Message: "document not found"})
		case errors.Is(err, ErrForbidden):
			writeJSON(w, http.StatusForbidden, api.APIResponse{Status: "error", Message: "access denied"})
		default:
			writeJSON(w, http.StatusInternalServerError, api.APIResponse{Status: "error", Message: err.Error()})
		}
		return
	}
	writeJSON(w, http.StatusAccepted, api.APIResponse{Status: "success", Message: "document processing started", Data: result})
}

// Delete godoc
//
//	@Summary		Hapus dokumen
//	@Description	Menghapus file dari object storage, embeddings, Parquet, dan record database
//	@Tags			documents
//	@Accept			json
//	@Produce		json
//	@Param			body	body		object{document_id=string,user_id=string}	true	"Document ID dan User ID"
//	@Success		200		{object}	api.APIResponse
//	@Failure		400		{object}	api.APIResponse
//	@Failure		403		{object}	api.APIResponse
//	@Failure		404		{object}	api.APIResponse
//	@Failure		500		{object}	api.APIResponse
//	@Security		BearerAuth
//	@Router			/api/v1/document/delete [delete]
func (h *Handler) Delete(w http.ResponseWriter, r *http.Request) {
	var req struct {
		DocumentID string `json:"document_id"`
		UserID     string `json:"user_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "invalid request body"})
		return
	}
	if req.DocumentID == "" || req.UserID == "" {
		writeJSON(w, http.StatusBadRequest, api.APIResponse{Status: "error", Message: "document_id and user_id are required"})
		return
	}
	if rejectUserMismatch(w, r, req.UserID) {
		return
	}

	if err := h.svc.Delete(r.Context(), req.DocumentID, req.UserID); err != nil {
		switch {
		case errors.Is(err, ErrNotFound):
			writeJSON(w, http.StatusNotFound, api.APIResponse{Status: "error", Message: "document not found"})
		case errors.Is(err, ErrForbidden):
			writeJSON(w, http.StatusForbidden, api.APIResponse{Status: "error", Message: "access denied"})
		default:
			writeJSON(w, http.StatusInternalServerError, api.APIResponse{Status: "error", Message: "delete failed"})
		}
		return
	}
	writeJSON(w, http.StatusOK, api.APIResponse{Status: "success", Message: "document deleted"})
}

func rejectUserMismatch(w http.ResponseWriter, r *http.Request, userID string) bool {
	if err := auth.MatchContextUserID(r.Context(), userID); err != nil {
		writeJSON(w, http.StatusForbidden, api.APIResponse{Status: "error", Message: "user_id does not match authenticated user"})
		return true
	}
	return false
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}