package http

import (
	"encoding/json"
	stdhttp "net/http"
	"strings"
	"time"

	"github.com/oklog/ulid/v2"

	"gitea.dcglab.co.uk/steve/restic-manager/internal/api"
	"gitea.dcglab.co.uk/steve/restic-manager/internal/auth"
	"gitea.dcglab.co.uk/steve/restic-manager/internal/store"
)

// enrollRequest is the body posted by the agent installer. The token
// was issued by the operator via the UI ("Add host" → P1-27); the
// host metadata comes from the agent's own sysinfo collection.
type enrollRequest struct {
	Token         string       `json:"token"`
	HostName      string       `json:"hostname"`
	OS            api.HostOS   `json:"os"`
	Arch          api.HostArch `json:"arch"`
	AgentVersion  string       `json:"agent_version"`
	ResticVersion string       `json:"restic_version"`
}

// enrollResponse hands the agent the credentials it'll use forever.
// AgentToken is shown exactly once; the server stores its hash.
// CertPinSHA256 is the SHA-256 of the server's certificate, base64;
// the agent pins this on every reconnect so a stolen DB at the
// control plane can't be replayed against an attacker's TLS endpoint.
type enrollResponse struct {
	HostID        string `json:"host_id"`
	AgentToken    string `json:"agent_token"`
	CertPinSHA256 string `json:"cert_pin_sha256,omitempty"`
}

// enrollOperatorRequest creates a one-time enrollment token for an
// operator who is about to install an agent. Authenticated UI route.
type enrollOperatorRequest struct {
	HostName string   `json:"hostname"`
	Tags     []string `json:"tags,omitempty"`
}

type enrollOperatorResponse struct {
	Token     string    `json:"token"`
	ExpiresAt time.Time `json:"expires_at"`
}

// handleAgentEnroll consumes a one-time token, persists a Host row,
// and returns persistent agent credentials. Open endpoint (no
// session) — the token is the credential.
func (s *Server) handleAgentEnroll(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	var req enrollRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSONError(w, stdhttp.StatusBadRequest, "invalid_json", err.Error())
		return
	}
	if req.Token == "" || req.HostName == "" || req.OS == "" || req.Arch == "" {
		writeJSONError(w, stdhttp.StatusBadRequest, "missing_field",
			"token, hostname, os, arch all required")
		return
	}

	hostID := ulid.Make().String()

	// Atomically: validate + consume token, then create the host.
	// We do these in two statements; if create-host fails, the token
	// is already burned. That's acceptable — operator just regens.
	tokHash := auth.HashToken(req.Token)
	if err := s.deps.Store.ConsumeEnrollmentToken(r.Context(), tokHash, hostID); err != nil {
		writeJSONError(w, stdhttp.StatusUnauthorized, "invalid_token",
			"token unknown, expired, or already used")
		return
	}

	// Mint the persistent agent bearer.
	agentToken, err := auth.NewToken()
	if err != nil {
		writeJSONError(w, stdhttp.StatusInternalServerError, "internal", "")
		return
	}

	host := store.Host{
		ID:            hostID,
		Name:          strings.TrimSpace(req.HostName),
		OS:            string(req.OS),
		Arch:          string(req.Arch),
		AgentVersion:  req.AgentVersion,
		ResticVersion: req.ResticVersion,
		EnrolledAt:    time.Now().UTC(),
	}
	if err := s.deps.Store.CreateHost(r.Context(), host,
		auth.HashToken(agentToken), ""); err != nil {
		writeJSONError(w, stdhttp.StatusConflict, "host_exists", err.Error())
		return
	}

	_ = s.deps.Store.AppendAudit(r.Context(), store.AuditEntry{
		ID:         ulid.Make().String(),
		Actor:      "system",
		Action:     "host.enrolled",
		TargetKind: ptr("host"),
		TargetID:   &hostID,
		TS:         host.EnrolledAt,
	})

	writeJSON(w, stdhttp.StatusCreated, enrollResponse{
		HostID:     hostID,
		AgentToken: agentToken,
		// CertPinSHA256 is populated by a TLS-aware future revision.
		// For now (HTTP-or-TLS-by-Caddy) we leave it empty and rely
		// on the agent trusting its OS root store.
	})
}

// handleCreateEnrollmentToken (operator-facing) — generates a
// short-lived token for a new host. Authenticated; admin/operator only.
//
// TODO: gate by authn middleware once login session lookup lands.
// For Phase 1's first slice, we accept the bootstrap-shipped admin
// session cookie and trust it, validating the cookie via store.
func (s *Server) handleCreateEnrollmentToken(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	if !s.authedUser(r) {
		writeJSONError(w, stdhttp.StatusUnauthorized, "unauthorized", "")
		return
	}

	var req enrollOperatorRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSONError(w, stdhttp.StatusBadRequest, "invalid_json", err.Error())
		return
	}

	token, err := auth.NewToken()
	if err != nil {
		writeJSONError(w, stdhttp.StatusInternalServerError, "internal", "")
		return
	}
	const ttl = time.Hour
	if err := s.deps.Store.CreateEnrollmentToken(r.Context(), auth.HashToken(token), ttl); err != nil {
		writeJSONError(w, stdhttp.StatusInternalServerError, "internal", "")
		return
	}

	writeJSON(w, stdhttp.StatusCreated, enrollOperatorResponse{
		Token:     token,
		ExpiresAt: time.Now().Add(ttl).UTC(),
	})
}

// authedUser returns true iff the request carries a valid session
// cookie. Minimal stub for now; full RBAC middleware lands with
// P4-03.
func (s *Server) authedUser(r *stdhttp.Request) bool {
	c, err := r.Cookie(sessionCookieName)
	if err != nil {
		return false
	}
	_, err = s.deps.Store.LookupSession(r.Context(), auth.HashToken(c.Value))
	return err == nil
}

func ptr(s string) *string { return &s }