package oci

import (
	"io"
	"net/http"
	"strings"

	"git.wntrmute.dev/kyle/mcr/internal/auth"
	"git.wntrmute.dev/kyle/mcr/internal/db"
	"git.wntrmute.dev/kyle/mcr/internal/policy"
	"git.wntrmute.dev/kyle/mcr/internal/storage"
)

// DBQuerier provides the database operations needed by OCI handlers.
type DBQuerier interface {
	GetRepositoryByName(name string) (int64, error)
	GetManifestByTag(repoID int64, tag string) (*db.ManifestRow, error)
	GetManifestByDigest(repoID int64, digest string) (*db.ManifestRow, error)
	BlobExistsInRepo(repoID int64, digest string) (bool, error)
	ListTags(repoID int64, after string, limit int) ([]string, error)
	ListRepositoryNames(after string, limit int) ([]string, error)

	// Push operations
	GetOrCreateRepository(name string) (int64, error)
	BlobExists(digest string) (bool, error)
	InsertBlob(digest string, size int64) error
	PushManifest(p db.PushManifestParams) error

	// Upload operations
	CreateUpload(uuid string, repoID int64) error
	GetUpload(uuid string) (*db.UploadRow, error)
	UpdateUploadOffset(uuid string, offset int64) error
	DeleteUpload(uuid string) error

	// Delete operations
	DeleteManifest(repoID int64, digest string) error
	DeleteBlobFromRepo(repoID int64, digest string) error
}

// BlobStore provides read and write access to blob storage.
type BlobStore interface {
	Open(digest string) (io.ReadCloser, error)
	Stat(digest string) (int64, error)
	StartUpload(uuid string) (*storage.BlobWriter, error)
}

// PolicyEval evaluates access control policies.
type PolicyEval interface {
	Evaluate(input policy.PolicyInput) (policy.Effect, *policy.Rule)
}

// AuditFunc records audit events. Follows the same signature pattern as
// db.WriteAuditEvent but without an error return — audit failures should
// not block request processing.
type AuditFunc func(eventType, actorID, repository, digest, ip string, details map[string]string)

// Handler serves OCI Distribution Spec endpoints.
type Handler struct {
	db      DBQuerier
	blobs   BlobStore
	policy  PolicyEval
	auditFn AuditFunc
	uploads *uploadManager
}

// NewHandler creates a new OCI handler.
func NewHandler(querier DBQuerier, blobs BlobStore, pol PolicyEval, auditFn AuditFunc) *Handler {
	return &Handler{
		db:      querier,
		blobs:   blobs,
		policy:  pol,
		auditFn: auditFn,
		uploads: newUploadManager(),
	}
}

// isDigest returns true if the reference looks like a digest (sha256:...).
func isDigest(ref string) bool {
	return strings.HasPrefix(ref, "sha256:")
}

// checkPolicy evaluates the policy for the given action and repository.
// Returns true if access is allowed, false if denied (and writes the OCI error).
func (h *Handler) checkPolicy(w http.ResponseWriter, r *http.Request, action policy.Action, repo string) bool {
	claims := auth.ClaimsFromContext(r.Context())
	if claims == nil {
		writeOCIError(w, "UNAUTHORIZED", http.StatusUnauthorized, "authentication required")
		return false
	}

	input := policy.PolicyInput{
		Subject:     claims.Subject,
		AccountType: claims.AccountType,
		Roles:       claims.Roles,
		Action:      action,
		Repository:  repo,
	}

	effect, _ := h.policy.Evaluate(input)
	if effect == policy.Deny {
		if h.auditFn != nil {
			h.auditFn("policy_deny", claims.Subject, repo, "", r.RemoteAddr, map[string]string{
				"action": string(action),
			})
		}
		writeOCIError(w, "DENIED", http.StatusForbidden, "access denied by policy")
		return false
	}
	return true
}

// audit records an audit event if an audit function is configured.
func (h *Handler) audit(r *http.Request, eventType, repo, digest string) {
	if h.auditFn == nil {
		return
	}
	claims := auth.ClaimsFromContext(r.Context())
	actorID := ""
	if claims != nil {
		actorID = claims.Subject
	}
	h.auditFn(eventType, actorID, repo, digest, r.RemoteAddr, nil)
}