package handler

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"path"
	"strings"

	"gitea.loveuer.com/loveuer/cluster/internal/database"
	"gitea.loveuer.com/loveuer/cluster/internal/model"
	"gitea.loveuer.com/loveuer/cluster/internal/rerr"

	"github.com/gofiber/fiber/v3"
	"gorm.io/gorm"
)

var ErrNotFound = errors.New("not found")

func handleBlobs(c fiber.Ctx) error {
	elem := strings.Split(c.Path(), "/")
	elem = elem[1:]
	if elem[len(elem)-1] == "" {
		elem = elem[:len(elem)-1]
	}

	// Must have a path of form /v2/{name}/blobs/{upload,sha256:}
	if len(elem) < 4 {
		return rerr.Error(c, &rerr.RepositoryError{
			Status:  http.StatusBadRequest,
			Code:    "NAME_INVALID",
			Message: "blobs must be attached to a repo",
		})
	}

	target := elem[len(elem)-1]
	service := elem[len(elem)-2]
	digest := c.Query("digest")
	contentRange := c.Get("Content-Range")
	rangeHeader := c.Get("Range")
	repo := strings.Join(elem[1:len(elem)-2], "/")

	switch c.Method() {
	case http.MethodHead:
		h, err := model.NewHash(target)
		if err != nil {
			return rerr.Error(c, &rerr.RepositoryError{
				Status:  http.StatusBadRequest,
				Code:    "NAME_INVALID",
				Message: "invalid digest",
			})
		}

		size, err := blobHandler.Stat(c.Context(), repo, h)
		if errors.Is(err, ErrNotFound) {
			return rerr.Error(c, rerr.ErrBlobUnknown)
		} else if err != nil {
			return rerr.Error(c, rerr.ErrInternal(err))
		}

		c.Set("Content-Length", fmt.Sprint(size))
		c.Set("Docker-Content-Digest", h.String())
		return c.Send(nil)

	case http.MethodGet:
		h, err := model.NewHash(target)
		if err != nil {
			return rerr.Error(c, &rerr.RepositoryError{
				Status:  http.StatusBadRequest,
				Code:    "NAME_INVALID",
				Message: "invalid digest",
			})
		}

		size, err := blobHandler.Stat(c.Context(), repo, h)
		if errors.Is(err, ErrNotFound) {
			return rerr.Error(c, rerr.ErrBlobUnknown)
		} else if err != nil {
			return rerr.Error(c, rerr.ErrInternal(err))
		}

		rc, err := blobHandler.Get(c.Context(), repo, h)
		if errors.Is(err, ErrNotFound) {
			return rerr.Error(c, rerr.ErrBlobUnknown)
		} else if err != nil {
			return rerr.Error(c, rerr.ErrInternal(err))
		}
		defer rc.Close()

		r := rc
		if rangeHeader != "" {
			start, end := int64(0), int64(0)
			if _, err := fmt.Sscanf(rangeHeader, "bytes=%d-%d", &start, &end); err != nil {
				return rerr.Error(c, &rerr.RepositoryError{
					Status:  http.StatusRequestedRangeNotSatisfiable,
					Code:    "BLOB_UNKNOWN",
					Message: "We don't understand your Range",
				})
			}

			n := (end + 1) - start
			if ra, ok := r.(io.ReaderAt); ok {
				if end+1 > size {
					return rerr.Error(c, &rerr.RepositoryError{
						Status:  http.StatusRequestedRangeNotSatisfiable,
						Code:    "BLOB_UNKNOWN",
						Message: fmt.Sprintf("range end %d > %d size", end+1, size),
					})
				}
				sr := io.NewSectionReader(ra, start, n)
				r = io.NopCloser(sr)
			} else {
				if _, err := io.CopyN(io.Discard, r, start); err != nil {
					return rerr.Error(c, &rerr.RepositoryError{
						Status:  http.StatusRequestedRangeNotSatisfiable,
						Code:    "BLOB_UNKNOWN",
						Message: fmt.Sprintf("Failed to discard %d bytes", start),
					})
				}
				lr := io.LimitReader(r, n)
				r = io.NopCloser(lr)
			}

			c.Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, size))
			c.Set("Content-Length", fmt.Sprint(n))
			c.Set("Docker-Content-Digest", h.String())
			c.Status(http.StatusPartialContent)
		} else {
			c.Set("Content-Length", fmt.Sprint(size))
			c.Set("Docker-Content-Digest", h.String())
			c.Status(http.StatusOK)
		}

		_, err = io.Copy(c, r)
		return err

	case http.MethodPost:
		if target != "uploads" {
			return rerr.Error(c, &rerr.RepositoryError{
				Status:  http.StatusBadRequest,
				Code:    "METHOD_UNKNOWN",
				Message: fmt.Sprintf("POST to /blobs must be followed by /uploads, got %s", target),
			})
		}

		if digest != "" {
			h, err := model.NewHash(digest)
			if err != nil {
				return rerr.Error(c, rerr.ErrDigestInvalid)
			}

			vrc := io.NopCloser(bytes.NewReader(c.Body()))
			defer vrc.Close()

			if err = blobHandler.Put(c.Context(), repo, h, vrc); err != nil {
				return rerr.Error(c, rerr.ErrInternal(err))
			}
			c.Set("Docker-Content-Digest", h.String())
			return c.SendStatus(http.StatusCreated)
		}

		id := uploadHandler.UploadId()

		// Get or create repository
		var repository model.RegistryRepository
		if err := database.DB.Where("name = ?", repo).First(&repository).Error; err != nil {
			if err == gorm.ErrRecordNotFound {
				repository = model.RegistryRepository{Name: repo}
				if err := database.DB.Create(&repository).Error; err != nil {
					if strings.Contains(err.Error(), "UNIQUE constraint failed") {
						if err := database.DB.Where("name = ?", repo).First(&repository).Error; err != nil {
							return rerr.Error(c, rerr.ErrInternal(err))
						}
					} else {
						return rerr.Error(c, rerr.ErrInternal(err))
					}
				}
			} else {
				return rerr.Error(c, rerr.ErrInternal(err))
			}
		}

		// Create upload session
		uploadPath := model.GetUploadPath("./x-storage", id)
		if err := os.MkdirAll(path.Dir(uploadPath), 0755); err != nil {
			return rerr.Error(c, rerr.ErrInternal(err))
		}

		session := model.RegistryUploadSession{
			RepositoryID: repository.ID,
			SessionID:    id,
			Path:         uploadPath,
			Size:         0,
		}
		if err := database.DB.Create(&session).Error; err != nil {
			return rerr.Error(c, rerr.ErrInternal(err))
		}

		c.Set("Location", "/"+path.Join("v2", path.Join(elem[1:len(elem)-2]...), "blobs/uploads", id))
		c.Set("Range", "0-0")

		return c.SendStatus(http.StatusAccepted)

	case http.MethodPatch:
		if service != "uploads" {
			return rerr.Error(c, &rerr.RepositoryError{
				Status:  http.StatusBadRequest,
				Code:    "METHOD_UNKNOWN",
				Message: fmt.Sprintf("PATCH to /blobs must be followed by /uploads, got %s", service),
			})
		}

		start, end := 0, 0
		if contentRange != "" {
			if _, err := fmt.Sscanf(contentRange, "%d-%d", &start, &end); err != nil {
				return rerr.Error(c, &rerr.RepositoryError{
					Status:  http.StatusRequestedRangeNotSatisfiable,
					Code:    "BLOB_UPLOAD_UNKNOWN",
					Message: "We don't understand your Content-Range",
				})
			}

			expectedEnd := start + len(c.Body()) - 1
			if end != expectedEnd {
				return rerr.Error(c, &rerr.RepositoryError{
					Status:  http.StatusRequestedRangeNotSatisfiable,
					Code:    "BLOB_UPLOAD_INVALID",
					Message: fmt.Sprintf("blob upload content range mismatch: expected end %d, got %d", expectedEnd, end),
				})
			}
		} else {
			end = start + len(c.Body()) - 1
		}

		length, re := uploadHandler.Write(c.Context(), target, bytes.NewReader(c.Body()), start, end)
		if re != nil {
			return rerr.Error(c, re)
		}

		c.Set("Location", "/"+path.Join("v2", path.Join(elem[1:len(elem)-3]...), "blobs/uploads", target))
		c.Set("Range", fmt.Sprintf("0-%d", length-1))
		return c.SendStatus(http.StatusNoContent)

	case http.MethodPut:
		if service != "uploads" {
			return rerr.Error(c, &rerr.RepositoryError{
				Status:  http.StatusBadRequest,
				Code:    "METHOD_UNKNOWN",
				Message: fmt.Sprintf("PUT to /blobs must be followed by /uploads, got %s", service),
			})
		}

		if digest == "" {
			return rerr.Error(c, &rerr.RepositoryError{
				Status:  http.StatusBadRequest,
				Code:    "DIGEST_INVALID",
				Message: "digest not specified",
			})
		}

		hash, err := model.NewHash(digest)
		if err != nil {
			return rerr.Error(c, &rerr.RepositoryError{
				Status:  http.StatusBadRequest,
				Code:    "NAME_INVALID",
				Message: "invalid digest",
			})
		}

		re := uploadHandler.Done(c.Context(), blobHandler, target, bytes.NewReader(c.Body()), len(c.Body()), repo, hash)
		if re != nil {
			return rerr.Error(c, re)
		}

		c.Set("Docker-Content-Digest", hash.String())
		return c.SendStatus(http.StatusCreated)

	default:
		return rerr.Error(c, &rerr.RepositoryError{
			Status:  http.StatusBadRequest,
			Code:    "METHOD_UNKNOWN",
			Message: "We don't understand your method + url",
		})
	}
}