package handlers

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"
	"xorm.io/xorm"

	"github.com/forgeo/forgebucket/internal/domain/signing"
	"github.com/forgeo/forgebucket/internal/models"
)

type ArtifactHandler struct {
	db           *xorm.Engine
	artifactRoot string
	keys         *signing.KeyStore
}

func NewArtifactHandler(db *xorm.Engine, artifactRoot string, keys *signing.KeyStore) *ArtifactHandler {
	return &ArtifactHandler{db: db, artifactRoot: artifactRoot, keys: keys}
}

// List returns all artifacts for a pipeline run.
func (h *ArtifactHandler) List(w http.ResponseWriter, r *http.Request) {
	repoID, runID, ok := h.resolveRunIDs(w, r)
	if !ok {
		return
	}
	var artifacts []models.Artifact
	if err := h.db.Where("run_id = ? AND repo_id = ?", runID, repoID).Find(&artifacts); err != nil {
		jsonError(w, "could not list artifacts", http.StatusInternalServerError)
		return
	}
	if artifacts == nil {
		artifacts = []models.Artifact{}
	}
	jsonOK(w, artifacts)
}

// Upload accepts a multipart file upload, stores it as an artifact, and
// immediately signs it using the server's signing key.
func (h *ArtifactHandler) Upload(w http.ResponseWriter, r *http.Request) {
	repoID, runID, ok := h.resolveRunIDs(w, r)
	if !ok {
		return
	}

	r.Body = http.MaxBytesReader(w, r.Body, 512<<20) // 512 MB max
	if err := r.ParseMultipartForm(32 << 20); err != nil {
		jsonError(w, "multipart parse failed", http.StatusBadRequest)
		return
	}
	file, header, err := r.FormFile("file")
	if err != nil {
		jsonError(w, "file field is required", http.StatusBadRequest)
		return
	}
	defer file.Close()

	name := r.FormValue("name")
	if name == "" {
		name = header.Filename
	}

	// Sanitize name: no path separators.
	for _, c := range []byte(name) {
		if c == '/' || c == '\\' || c == 0 {
			jsonError(w, "artifact name must not contain path separators", http.StatusBadRequest)
			return
		}
	}

	dir := filepath.Join(h.artifactRoot, fmt.Sprintf("%d", runID))
	if err := os.MkdirAll(dir, 0755); err != nil {
		jsonError(w, "could not create storage directory", http.StatusInternalServerError)
		return
	}

	storagePath := filepath.Join(dir, name)
	dst, err := os.Create(storagePath)
	if err != nil {
		jsonError(w, "could not create file", http.StatusInternalServerError)
		return
	}
	defer dst.Close()

	// Read into memory so we can both write to disk and sign.
	content, err := io.ReadAll(file)
	if err != nil {
		jsonError(w, "could not read upload", http.StatusInternalServerError)
		return
	}
	if _, err := dst.Write(content); err != nil {
		jsonError(w, "could not write file", http.StatusInternalServerError)
		return
	}

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

	// Store path relative to artifactRoot for portability.
	relPath := fmt.Sprintf("%d/%s", runID, name)

	artifact := &models.Artifact{
		RunID:       runID,
		RepoID:      repoID,
		Name:        name,
		StoragePath: relPath,
		Size:        int64(len(content)),
		ContentType: ct,
	}
	if _, err := h.db.Insert(artifact); err != nil {
		jsonError(w, "could not record artifact", http.StatusInternalServerError)
		return
	}

	// Sign the artifact and persist the bundle.
	go h.signArtifact(artifact.ID, name, content)

	w.WriteHeader(http.StatusCreated)
	jsonOK(w, artifact)
}

// signArtifact is called in a goroutine after a successful upload.
func (h *ArtifactHandler) signArtifact(artifactID int64, name string, content []byte) {
	bundle, err := h.keys.Sign(artifactID, name, content)
	if err != nil {
		fmt.Printf("signing: failed to sign artifact %d: %v\n", artifactID, err)
		return
	}
	bundleJSON, err := json.Marshal(bundle)
	if err != nil {
		fmt.Printf("signing: failed to marshal bundle for artifact %d: %v\n", artifactID, err)
		return
	}
	sig := &models.ArtifactSignature{
		ArtifactID: artifactID,
		KeyID:      bundle.KeyID,
		Algorithm:  "ecdsa-p256-sha256",
		Digest:     bundle.Payload.Digest,
		BundleJSON: string(bundleJSON),
		SignedAt:   time.Now().UTC(),
	}
	if _, err := h.db.Insert(sig); err != nil {
		fmt.Printf("signing: failed to store signature for artifact %d: %v\n", artifactID, err)
	}
}

// Download streams the artifact file to the client.
func (h *ArtifactHandler) Download(w http.ResponseWriter, r *http.Request) {
	artifactID, err := strconv.ParseInt(chi.URLParam(r, "artifactID"), 10, 64)
	if err != nil {
		jsonError(w, "invalid artifact ID", http.StatusBadRequest)
		return
	}
	var artifact models.Artifact
	if found, _ := h.db.ID(artifactID).Get(&artifact); !found {
		jsonError(w, "artifact not found", http.StatusNotFound)
		return
	}

	fullPath := filepath.Join(h.artifactRoot, filepath.FromSlash(artifact.StoragePath))
	if !isUnder(h.artifactRoot, fullPath) {
		jsonError(w, "forbidden", http.StatusForbidden)
		return
	}

	f, err := os.Open(fullPath)
	if err != nil {
		jsonError(w, "artifact file not found", http.StatusNotFound)
		return
	}
	defer f.Close()

	ct := artifact.ContentType
	if ct == "" {
		ct = "application/octet-stream"
	}
	w.Header().Set("Content-Type", ct)
	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename=%q`, artifact.Name))
	w.Header().Set("Content-Length", strconv.FormatInt(artifact.Size, 10))
	io.Copy(w, f) //nolint:errcheck
}

// GetSignature returns the full signature bundle JSON for an artifact.
// GET /api/v1/repos/{owner}/{repo}/artifacts/{artifactID}/signature
func (h *ArtifactHandler) GetSignature(w http.ResponseWriter, r *http.Request) {
	artifactID, err := strconv.ParseInt(chi.URLParam(r, "artifactID"), 10, 64)
	if err != nil {
		jsonError(w, "invalid artifact ID", http.StatusBadRequest)
		return
	}

	var sig models.ArtifactSignature
	found, err := h.db.Where("artifact_id = ?", artifactID).Get(&sig)
	if err != nil {
		jsonError(w, "database error", http.StatusInternalServerError)
		return
	}
	if !found {
		jsonError(w, "signature not found — artifact may still be pending signing", http.StatusNotFound)
		return
	}

	// Return the raw bundle JSON so clients can verify independently.
	w.Header().Set("Content-Type", "application/vnd.forgebucket.signature.bundle+json")
	w.WriteHeader(http.StatusOK)
	w.Write([]byte(sig.BundleJSON)) //nolint:errcheck
}

// VerifySignature verifies the stored signature bundle for an artifact.
// GET /api/v1/repos/{owner}/{repo}/artifacts/{artifactID}/verify
func (h *ArtifactHandler) VerifySignature(w http.ResponseWriter, r *http.Request) {
	artifactID, err := strconv.ParseInt(chi.URLParam(r, "artifactID"), 10, 64)
	if err != nil {
		jsonError(w, "invalid artifact ID", http.StatusBadRequest)
		return
	}

	var sig models.ArtifactSignature
	found, err := h.db.Where("artifact_id = ?", artifactID).Get(&sig)
	if err != nil {
		jsonError(w, "database error", http.StatusInternalServerError)
		return
	}
	if !found {
		jsonError(w, "signature not found", http.StatusNotFound)
		return
	}

	result, err := h.keys.Verify([]byte(sig.BundleJSON))
	if err != nil {
		jsonError(w, fmt.Sprintf("verification error: %v", err), http.StatusUnprocessableEntity)
		return
	}

	jsonOK(w, result)
}

// ─── helpers ─────────────────────────────────────────────────────────────────

func (h *ArtifactHandler) resolveRunIDs(w http.ResponseWriter, r *http.Request) (repoID, runID int64, ok bool) {
	rID, ok := resolveRepoID(h.db, w, r)
	if !ok {
		return 0, 0, false
	}
	runID, err := strconv.ParseInt(chi.URLParam(r, "runID"), 10, 64)
	if err != nil {
		jsonError(w, "invalid run ID", http.StatusBadRequest)
		return 0, 0, false
	}
	return rID, runID, true
}

func isUnder(root, path string) bool {
	root = filepath.Clean(root)
	path = filepath.Clean(path)
	if len(path) <= len(root) {
		return false
	}
	return path[:len(root)] == root && path[len(root)] == filepath.Separator
}