package api

import (
	"errors"
	"net/http"
	"time"

	"github.com/gin-gonic/gin"

	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
	"gitea.stevedudenhoeffer.com/steve/pansy/internal/imagenorm"
	"gitea.stevedudenhoeffer.com/steve/pansy/internal/service"
)

// Seed-packet capture (#81). Two steps, deliberately separate:
//   POST /seed-lots/scan          multipart image → a proposal (reads only)
//   POST /seed-lots/from-packet   confirmed proposal → a plant + lot
// The scan never writes; creation happens only from an explicit confirm, so a
// misread can't add anything to the catalog on its own.

// scanUploadLimit bounds the multipart body. imagenorm caps the decoded image at
// 25 MiB; this is a little over that for the multipart envelope. A phone photo is
// a few MB, so this is generous.
const scanUploadLimit = 30 << 20

// scanReadTimeout is how long we allow the image upload to take. The server's
// default ReadTimeout (15s) is fine for JSON but tight for a multi-megabyte photo
// on a slow phone connection, so this endpoint extends it — the same
// ResponseController mechanism the SSE path uses for writes (#78).
const scanReadTimeout = 60 * time.Second

// scanWriteTimeout extends the write deadline for the same reason. The server's
// absolute WriteTimeout (30s) is measured from the start of the request, but this
// handler's response can't be written until AFTER a slow upload AND a live vision
// call — together easily past 30s. Without this, a successful extraction's
// response is silently dropped: the exact failure mode #78 fixed for SSE.
const scanWriteTimeout = 120 * time.Second

// scanSeedPacket reads an uploaded packet photo and returns a proposal.
func (h *handlers) scanSeedPacket(c *gin.Context) {
	// Extend both deadlines for the (potentially large, potentially slow) upload
	// and the live vision call that follows. Best-effort: if the writer doesn't
	// support it, the server defaults apply.
	rc := http.NewResponseController(c.Writer)
	_ = rc.SetReadDeadline(time.Now().Add(scanReadTimeout))
	_ = rc.SetWriteDeadline(time.Now().Add(scanWriteTimeout))

	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, scanUploadLimit)
	file, err := c.FormFile("image")
	if err != nil {
		// A body over scanUploadLimit trips MaxBytesReader — that's 413, not a
		// malformed request. Everything else here is a genuinely missing/garbled
		// multipart field.
		var tooBig *http.MaxBytesError
		if errors.As(err, &tooBig) {
			writeAPIError(c, http.StatusRequestEntityTooLarge, "IMAGE_TOO_LARGE", "that image is too large — try a smaller photo")
			return
		}
		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "attach an image as the \"image\" field")
		return
	}
	f, err := file.Open()
	if err != nil {
		// Opening the parsed upload failed on our side, not the client's.
		writeAPIError(c, http.StatusInternalServerError, "INTERNAL", "could not read the uploaded image")
		return
	}
	defer f.Close()

	// Normalize to JPEG (decodes HEIC/webp/png/jpeg, downscales, re-encodes) so
	// everything downstream — including the vision model — only sees a format it
	// can read. This is where an iPhone HEIC becomes usable.
	jpeg, _, err := imagenorm.Normalize(f, imagenorm.Options{})
	if err != nil {
		switch {
		case errors.Is(err, imagenorm.ErrTooLarge):
			writeAPIError(c, http.StatusRequestEntityTooLarge, "IMAGE_TOO_LARGE", "that image is too large — try a smaller photo")
		case errors.Is(err, imagenorm.ErrUnsupported):
			writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "that doesn't look like an image we can read (JPEG, PNG, HEIC or WebP)")
		default:
			// A read or re-encode fault is ours, not bad input.
			writeAPIError(c, http.StatusInternalServerError, "INTERNAL", "could not process the uploaded image")
		}
		return
	}

	prop, err := h.svc.ExtractSeedPacket(c.Request.Context(), mustActor(c).ID, jpeg)
	if err != nil {
		// A missing vision model surfaces as ErrInvalidInput from the service; give
		// it a clearer message than the generic 400, since the UI shouldn't have
		// offered the button at all in that case.
		if errors.Is(err, domain.ErrInvalidInput) {
			writeAPIError(c, http.StatusServiceUnavailable, "VISION_DISABLED", "packet scanning isn't set up on this instance")
			return
		}
		writeServiceError(c, err)
		return
	}
	c.JSON(http.StatusOK, prop)
}

// fromPacketRequest confirms a proposal: exactly one of plantId (attach to an
// existing plant) or newPlant (create a variety), plus the lot to record. The lot
// is seedLotFields — the create body's lot half WITHOUT plantId, since the plant
// comes from the plantId/newPlant choice, not the lot body.
type fromPacketRequest struct {
	PlantID  *int64              `json:"plantId"`
	NewPlant *plantCreateRequest `json:"newPlant"`
	Lot      seedLotFields       `json:"lot"`
}

// createFromPacket turns a confirmed proposal into a plant + lot.
func (h *handlers) createFromPacket(c *gin.Context) {
	var req fromPacketRequest
	if err := c.ShouldBindJSON(&req); err != nil {
		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "a lot and exactly one of plantId or newPlant are required")
		return
	}

	confirm := service.PacketConfirm{
		PlantID: req.PlantID,
		Lot:     req.Lot.toInput(), // no plantId in the lot body; the service attributes it
	}
	if req.NewPlant != nil {
		in := req.NewPlant.toInput()
		confirm.NewPlant = &in
	}

	res, err := h.svc.CreateFromPacket(c.Request.Context(), mustActor(c).ID, confirm)
	if err != nil {
		writeServiceError(c, err)
		return
	}
	c.JSON(http.StatusCreated, res)
}