package http

import (
	"encoding/json"
	"io"
	"net/http"
	"strconv"
	"strings"
	"time"

	"gis/internal/domain"
	"gis/internal/service"
	"gis/pkg/httputil"

	"github.com/go-chi/chi/v5"
	"github.com/go-playground/validator/v10"
	"github.com/google/uuid"
)

// maxUploadBytes caps the in-memory portion of a multipart upload (64 MiB).
const maxUploadBytes = 64 << 20

// DatasetHandler serves the /datasets routes.
type DatasetHandler struct {
	svc      *service.DatasetService
	validate *validator.Validate
}

// NewDatasetHandler returns a DatasetHandler.
func NewDatasetHandler(svc *service.DatasetService, validate *validator.Validate) *DatasetHandler {
	return &DatasetHandler{svc: svc, validate: validate}
}

// Register mounts the dataset routes on r.
func (h *DatasetHandler) Register(r chi.Router) {
	r.Get("/", h.list)
	r.Post("/", h.upload)
	r.Get("/{id}", h.get)
	r.Get("/{id}/status", h.status)
	r.Get("/{id}/download", h.download)
	r.Post("/{id}/mapping", h.mapping)
	r.Get("/{id}/observations", h.observations)
	r.Delete("/{id}", h.delete)
}

// status long-polls the dataset's processing status. With ?current=<status> it
// holds the request until the status changes (or ?wait=<seconds> elapses,
// default 25, max 60); without it, it returns the current status immediately.
func (h *DatasetHandler) status(w http.ResponseWriter, r *http.Request) {
	id, ok := parseUUIDParam(w, r, "id")
	if !ok {
		return
	}

	current := r.URL.Query().Get("current")

	var wait time.Duration
	if raw := r.URL.Query().Get("wait"); raw != "" {
		secs, err := strconv.Atoi(raw)
		if err != nil || secs < 0 {
			httputil.WriteError(w, http.StatusBadRequest, "invalid wait")
			return
		}
		wait = time.Duration(secs) * time.Second
	}

	info, err := h.svc.WaitForStatus(r.Context(), id, current, wait)
	if err != nil {
		respondDomainError(w, err)
		return
	}
	httputil.WriteJSON(w, http.StatusOK, info)
}

type yearColumnInput struct {
	Column string `json:"column" validate:"required"`
	Date   string `json:"date" validate:"required,datetime=2006-01-02"`
}

type mappingRequest struct {
	KatoColumn  string            `json:"kato_column" validate:"required"`
	YearColumns []yearColumnInput `json:"year_columns" validate:"required,min=1,dive"`
}

// mapping saves the KATO column and year-column mapping for a vector_with_kato
// dataset, moving it to ready.
func (h *DatasetHandler) mapping(w http.ResponseWriter, r *http.Request) {
	id, ok := parseUUIDParam(w, r, "id")
	if !ok {
		return
	}
	req, err := httputil.DecodeJSON[mappingRequest](w, r)
	if err != nil {
		httputil.WriteError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if err := h.validate.Struct(req); err != nil {
		httputil.WriteValidationErrors(w, err)
		return
	}

	in := service.MappingInput{KatoColumn: req.KatoColumn}
	for _, yc := range req.YearColumns {
		in.YearColumns = append(in.YearColumns, domain.YearColumn{Column: yc.Column, Date: yc.Date})
	}

	dataset, err := h.svc.SaveMapping(r.Context(), id, in)
	if err != nil {
		respondDomainError(w, err)
		return
	}
	httputil.WriteJSON(w, http.StatusOK, dataset)
}

func (h *DatasetHandler) upload(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseMultipartForm(maxUploadBytes); err != nil {
		httputil.WriteError(w, http.StatusBadRequest, "request must be multipart/form-data")
		return
	}

	categoryRaw := r.FormValue("category_id")
	categoryID, err := uuid.Parse(categoryRaw)
	if err != nil {
		httputil.WriteError(w, http.StatusUnprocessableEntity, "category_id must be a valid UUID")
		return
	}

	fileType := domain.FileType(r.FormValue("file_type"))
	if !fileType.Valid() {
		httputil.WriteError(w, http.StatusUnprocessableEntity, "file_type must be one of: vector_with_kato, vector, raster")
		return
	}

	meta, ok := optionalJSONFormValue(w, r, "meta")
	if !ok {
		return
	}

	automated, err := optionalBoolFormValue(r, "automated")
	if err != nil {
		httputil.WriteError(w, http.StatusUnprocessableEntity, "automated must be a boolean")
		return
	}

	file, header, err := r.FormFile("file")
	if err != nil {
		httputil.WriteError(w, http.StatusBadRequest, "file is required")
		return
	}
	defer file.Close()

	contentType := header.Header.Get("Content-Type")
	if contentType == "" {
		contentType = "application/octet-stream"
	}

	dataset, err := h.svc.Upload(r.Context(), service.UploadInput{
		CategoryID:  categoryID,
		Name:        r.FormValue("name"),
		Description: optionalFormValue(r, "description"),
		Unit:        optionalFormValue(r, "unit"),
		Meta:        meta,
		Automated:   automated,
		Filename:    header.Filename,
		FileType:    fileType,
		ContentType: contentType,
		Size:        header.Size,
		Reader:      file,
	})
	if err != nil {
		respondDomainError(w, err)
		return
	}
	httputil.WriteJSON(w, http.StatusCreated, dataset)
}

// optionalFormValue returns a pointer to a trimmed form value, or nil when the
// field is absent or blank, so nullable columns stay NULL.
func optionalFormValue(r *http.Request, name string) *string {
	v := strings.TrimSpace(r.FormValue(name))
	if v == "" {
		return nil
	}
	return &v
}

// optionalJSONFormValue reads a form field expected to contain JSON. A blank
// value yields (nil, true); invalid JSON writes a 422 and yields (nil, false).
func optionalJSONFormValue(w http.ResponseWriter, r *http.Request, name string) (json.RawMessage, bool) {
	v := strings.TrimSpace(r.FormValue(name))
	if v == "" {
		return nil, true
	}
	if !json.Valid([]byte(v)) {
		httputil.WriteError(w, http.StatusUnprocessableEntity, name+" must be valid JSON")
		return nil, false
	}
	return json.RawMessage(v), true
}

// optionalBoolFormValue parses an optional boolean form field, defaulting to
// false when the field is absent or blank.
func optionalBoolFormValue(r *http.Request, name string) (bool, error) {
	v := strings.TrimSpace(r.FormValue(name))
	if v == "" {
		return false, nil
	}
	return strconv.ParseBool(v)
}

func (h *DatasetHandler) list(w http.ResponseWriter, r *http.Request) {
	categoryID, ok := parseOptionalUUIDQuery(w, r, "category_id")
	if !ok {
		return
	}
	var categoryCode *string
	if v := strings.TrimSpace(r.URL.Query().Get("category_code")); v != "" {
		categoryCode = &v
	}
	page, ok := parsePositiveIntQuery(w, r, "page", 1)
	if !ok {
		return
	}
	pageSize, ok := parsePositiveIntQuery(w, r, "page_size", service.DefaultPageSize)
	if !ok {
		return
	}

	res, err := h.svc.ListSummaries(r.Context(), categoryID, categoryCode, page, pageSize)
	if err != nil {
		respondDomainError(w, err)
		return
	}
	httputil.WriteJSON(w, http.StatusOK, newPaginated(res.Items, res.Page, res.PageSize, res.Total))
}

func (h *DatasetHandler) observations(w http.ResponseWriter, r *http.Request) {
	id, ok := parseUUIDParam(w, r, "id")
	if !ok {
		return
	}
	page, ok := parsePositiveIntQuery(w, r, "page", 1)
	if !ok {
		return
	}
	pageSize, ok := parsePositiveIntQuery(w, r, "page_size", service.DefaultPageSize)
	if !ok {
		return
	}

	var katoCode *string
	if v := strings.TrimSpace(r.URL.Query().Get("kato_code")); v != "" {
		katoCode = &v
	}

	res, err := h.svc.ListObservations(r.Context(), id, katoCode, page, pageSize)
	if err != nil {
		respondDomainError(w, err)
		return
	}
	httputil.WriteJSON(w, http.StatusOK, newPaginated(res.Items, res.Page, res.PageSize, res.Total))
}

func (h *DatasetHandler) get(w http.ResponseWriter, r *http.Request) {
	id, ok := parseUUIDParam(w, r, "id")
	if !ok {
		return
	}
	dataset, err := h.svc.Get(r.Context(), id)
	if err != nil {
		respondDomainError(w, err)
		return
	}
	httputil.WriteJSON(w, http.StatusOK, dataset)
}

func (h *DatasetHandler) download(w http.ResponseWriter, r *http.Request) {
	id, ok := parseUUIDParam(w, r, "id")
	if !ok {
		return
	}
	dataset, obj, err := h.svc.Download(r.Context(), id)
	if err != nil {
		respondDomainError(w, err)
		return
	}
	defer obj.Close()

	w.Header().Set("Content-Type", dataset.ContentType)
	w.Header().Set("Content-Disposition", `attachment; filename="`+dataset.Filename+`"`)
	if dataset.SizeBytes > 0 {
		w.Header().Set("Content-Length", strconv.FormatInt(dataset.SizeBytes, 10))
	}
	if _, err := io.Copy(w, obj); err != nil {
		// Headers are already sent; nothing useful to return to the client.
		return
	}
}

func (h *DatasetHandler) delete(w http.ResponseWriter, r *http.Request) {
	id, ok := parseUUIDParam(w, r, "id")
	if !ok {
		return
	}
	if err := h.svc.Delete(r.Context(), id); err != nil {
		respondDomainError(w, err)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}