package http

import (
	"context"
	"encoding/json"
	"log/slog"
	"time"

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

// loadScheduleSetPayload reads the host's current schedule set + the
// canonical version into a wire-shape payload. Returns an empty
// (but well-formed) payload with version 0 if the host has nothing
// scheduled yet — that's still a valid state to push so the agent
// drops any stale cron entries from a previous deployment.
func (s *Server) loadScheduleSetPayload(ctx context.Context, hostID string) (api.ScheduleSetPayload, error) {
	rows, err := s.deps.Store.ListSchedulesByHost(ctx, hostID)
	if err != nil {
		return api.ScheduleSetPayload{}, err
	}
	version, err := s.deps.Store.GetHostScheduleVersion(ctx, hostID)
	if err != nil {
		return api.ScheduleSetPayload{}, err
	}
	out := api.ScheduleSetPayload{
		Version:   version,
		Schedules: make([]api.Schedule, 0, len(rows)),
	}
	for _, r := range rows {
		retJSON, _ := json.Marshal(r.RetentionPolicy)
		optJSON, _ := json.Marshal(r.Options)
		out.Schedules = append(out.Schedules, api.Schedule{
			ID:              r.ID,
			Kind:            api.JobKind(r.Kind),
			CronExpr:        r.CronExpr,
			Paths:           r.Paths,
			Excludes:        r.Excludes,
			Tags:            r.Tags,
			RetentionPolicy: retJSON,
			Options:         optJSON,
			PreHook:         r.PreHook,
			PostHook:        r.PostHook,
			Enabled:         r.Enabled,
		})
	}
	return out, nil
}

// pushScheduleSet ships the current schedule list to the agent over
// the hub. Caller has already determined the agent is connected.
// Errors are logged and returned; the next push (or the next hello)
// will retry. Idempotent — sending the same version twice is a
// harmless no-op on the agent side.
func (s *Server) pushScheduleSet(ctx context.Context, hostID string) error {
	pl, err := s.loadScheduleSetPayload(ctx, hostID)
	if err != nil {
		slog.Warn("push schedule.set: load failed", "host_id", hostID, "err", err)
		return err
	}
	env, err := api.Marshal(api.MsgScheduleSet, "", pl)
	if err != nil {
		return err
	}
	sendCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()
	if err := s.deps.Hub.Send(sendCtx, hostID, env); err != nil {
		slog.Warn("push schedule.set: hub send failed",
			"host_id", hostID, "version", pl.Version, "err", err)
		return err
	}
	return nil
}

// pushScheduleSetOnConn is the on-hello flavour: writes directly to
// the just-handshaken conn rather than racing through the hub. Used
// by onAgentHello so a brand-new connection can't miss an early
// push because Register hasn't completed yet.
func (s *Server) pushScheduleSetOnConn(ctx context.Context, hostID string, conn *ws.Conn) {
	pl, err := s.loadScheduleSetPayload(ctx, hostID)
	if err != nil {
		slog.Warn("on-hello: load schedules", "host_id", hostID, "err", err)
		return
	}
	env, err := api.Marshal(api.MsgScheduleSet, "", pl)
	if err != nil {
		slog.Error("on-hello: marshal schedule.set", "host_id", hostID, "err", err)
		return
	}
	sendCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()
	if err := conn.Send(sendCtx, env); err != nil {
		slog.Warn("on-hello: send schedule.set",
			"host_id", hostID, "version", pl.Version, "err", err)
	}
}

// pushIfConnected dispatches a schedule.set push asynchronously when
// the agent is online. Used by CRUD handlers: a missed push is
// non-fatal because the next reconnect's on-hello path will catch
// the agent up. Decoupled from the request so the operator's HTTP
// response doesn't wait on the WS round-trip.
func (s *Server) pushScheduleSetAsync(hostID string) {
	if s.deps.Hub == nil || !s.deps.Hub.Connected(hostID) {
		return
	}
	go func() {
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		_ = s.pushScheduleSet(ctx, hostID)
	}()
}

// applyScheduleAck records the version the agent has confirmed via
// schedule.ack. Called from the WS dispatcher (wired below). A bad
// version (zero, or higher than what we've issued) is logged but
// not fatal — the next push will set the agent straight.
func (s *Server) applyScheduleAck(ctx context.Context, hostID string, version int64, appliedAt time.Time) {
	if version <= 0 {
		return
	}
	canonical, err := s.deps.Store.GetHostScheduleVersion(ctx, hostID)
	if err != nil {
		slog.Warn("schedule.ack: load canonical version",
			"host_id", hostID, "err", err)
		return
	}
	if version > canonical {
		slog.Warn("schedule.ack: agent reported version ahead of server",
			"host_id", hostID, "agent", version, "server", canonical)
		return
	}
	if err := s.deps.Store.SetHostAppliedScheduleVersion(ctx, hostID, version); err != nil {
		slog.Warn("schedule.ack: persist applied version",
			"host_id", hostID, "version", version, "err", err)
		return
	}
	slog.Info("schedule.ack: applied",
		"host_id", hostID, "version", version, "applied_at", appliedAt)
}

// Compile-time guard that the store actually implements the methods
// schedule_push.go calls. Useful when mocking the store in tests.
var _ scheduleStore = (*store.Store)(nil)

type scheduleStore interface {
	ListSchedulesByHost(ctx context.Context, hostID string) ([]store.Schedule, error)
	GetHostScheduleVersion(ctx context.Context, hostID string) (int64, error)
	SetHostAppliedScheduleVersion(ctx context.Context, hostID string, version int64) error
}