package store

import (
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"

	"git.ipao.vip/rogee/go-sip/internal/configread"
	"git.ipao.vip/rogee/go-sip/internal/contract"
	"git.ipao.vip/rogee/go-sip/internal/tenant"
)

var ErrControlRejected = errors.New("task control rejected by durable task state")

// CompleteStart binds a freshly verified task to its predeclared queue and
// records the control acknowledgment together. It never reopens a task
// that is currently paused or stopped.
func (s *Store) CompleteStart(snapshot configread.Snapshot, eventID string) error {
	task := snapshot.Task
	if task.Status != "running" {
		return fmt.Errorf("%w: start requires a running task", ErrControlRejected)
	}
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	var state, status string
	err = tx.QueryRow(`SELECT control_state,status FROM dispatcher_tasks WHERE dispatcher_id=? AND tenant_id=? AND task_id=?`, task.DispatcherID, task.TenantID, task.TaskID).Scan(&state, &status)
	if err != nil && !errors.Is(err, sql.ErrNoRows) {
		return fmt.Errorf("check start task state: %w", err)
	}
	if err == nil && (state != "" || status != "running") {
		return fmt.Errorf("%w: start cannot reopen a paused or stopped task", ErrControlRejected)
	}
	if err := applyDiscoveredTasks(tx, task.DispatcherID, []configread.DiscoveredTask{{TenantID: task.TenantID, TaskID: task.TaskID, TaskRevision: task.TaskRevision, Status: task.Status}}); err != nil {
		return err
	}
	if err := enqueueControlAck(tx, task.DispatcherID, task.TenantID, eventID, "applied"); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("commit started task and control acknowledgment: %w", err)
	}
	return nil
}

// PrepareControl closes only this task's admission before requesting the
// Agent action. No successful control acknowledgment exists at this point.
// Repeated commands are prepared and dispatched again; this is not control
// deduplication or an expected-revision/CAS API.
func (s *Store) PrepareControl(dispatcherID string, tenantID int64, taskID, action string) error {
	if dispatcherID == "" || tenantID <= 0 || taskID == "" {
		return errors.New("invalid task control identity")
	}
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	var state, status string
	var revision int64
	var present int
	err = tx.QueryRow(`SELECT control_state,status,task_revision,present FROM dispatcher_tasks
        WHERE dispatcher_id=? AND tenant_id=? AND task_id=?`, dispatcherID, tenantID, taskID).Scan(&state, &status, &revision, &present)
	if err != nil {
		return fmt.Errorf("load task control state: %w", err)
	}
	if present != 1 {
		return fmt.Errorf("%w: task is not in the assigned discovery list", ErrControlRejected)
	}
	var prepared string
	switch action {
	case "pause":
		if state == "stopped" || state == "stopping" {
			return fmt.Errorf("%w: stopped task cannot be paused", ErrControlRejected)
		}
		prepared = "pausing"
	case "stop":
		prepared = "stopping"
	case "resume":
		if state != "paused" && state != "resuming" {
			return fmt.Errorf("%w: resume requires a persistently paused, non-stopped task", ErrControlRejected)
		}
		if status != "running" {
			return fmt.Errorf("%w: fresh task is not running", ErrControlRejected)
		}
		var configuredRevision int64
		err = tx.QueryRow(`SELECT task_revision FROM dispatcher_configs WHERE dispatcher_id=? AND tenant_id=? AND task_id=?`, dispatcherID, tenantID, taskID).Scan(&configuredRevision)
		if err != nil || configuredRevision != revision {
			return errors.New("resume requires the latest verified task configuration")
		}
		prepared = "resuming"
	default:
		return fmt.Errorf("invalid task control action %q", action)
	}
	if _, err := tx.Exec(`UPDATE dispatcher_tasks SET control_state=? WHERE dispatcher_id=? AND tenant_id=? AND task_id=?`, prepared, dispatcherID, tenantID, taskID); err != nil {
		return fmt.Errorf("persist task control barrier: %w", err)
	}
	if action == "stop" {
		if _, err := tx.Exec(`UPDATE dispatcher_inbox SET status='suppressed' WHERE dispatcher_id=? AND tenant_id=? AND task_id=? AND status='pending'`, dispatcherID, tenantID, taskID); err != nil {
			return fmt.Errorf("suppress unstarted stopped-task commands: %w", err)
		}
	}
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("commit task control barrier: %w", err)
	}
	return nil
}

// CompleteControl atomically records the applied state and durable outbox
// only after an Agent control RPC accepted the action. It does not claim that
// active-call drain or hangup has already finished.
func (s *Store) CompleteControl(dispatcherID string, tenantID int64, taskID, action, eventID string) error {
	var expected, final string
	switch action {
	case "pause":
		expected, final = "pausing", "paused"
	case "stop":
		expected, final = "stopping", "stopped"
	case "resume":
		expected, final = "resuming", ""
	default:
		return fmt.Errorf("invalid task control action %q", action)
	}
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	var state, status string
	err = tx.QueryRow(`SELECT control_state,status FROM dispatcher_tasks WHERE dispatcher_id=? AND tenant_id=? AND task_id=? AND present=1`, dispatcherID, tenantID, taskID).Scan(&state, &status)
	if err != nil {
		return fmt.Errorf("read prepared task control: %w", err)
	}
	if state != expected || (action == "resume" && status != "running") {
		return fmt.Errorf("task %q control %q is no longer prepared or authorized", taskID, action)
	}
	if _, err := tx.Exec(`UPDATE dispatcher_tasks SET control_state=? WHERE dispatcher_id=? AND tenant_id=? AND task_id=?`, final, dispatcherID, tenantID, taskID); err != nil {
		return fmt.Errorf("persist applied task control: %w", err)
	}
	if err := enqueueControlAck(tx, dispatcherID, tenantID, eventID, "applied"); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("commit task control and outbox: %w", err)
	}
	return nil
}

func (s *Store) RejectControl(dispatcherID string, tenantID int64, eventID string) error {
	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	if err := enqueueControlAck(tx, dispatcherID, tenantID, eventID, "rejected"); err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return fmt.Errorf("commit rejected task control: %w", err)
	}
	return nil
}

func enqueueControlAck(tx *sql.Tx, dispatcherID string, tenantID int64, eventID, status string) error {
	if eventID == "" || len(eventID) > 255 || tenantID <= 0 || (status != "applied" && status != "rejected") {
		return errors.New("invalid task control acknowledgment identity or status")
	}
	route, err := tenant.ResultRoute(dispatcherID)
	if err != nil {
		return err
	}
	body, err := json.Marshal(struct {
		EventID      string `json:"event_id"`
		EventType    string `json:"event_type"`
		DispatcherID string `json:"dispatcher_id"`
		TenantID     int64  `json:"tenant_id"`
		Payload      struct {
			Status string `json:"status"`
		} `json:"payload"`
	}{EventID: eventID, EventType: "task.control", DispatcherID: dispatcherID, TenantID: tenantID, Payload: struct {
		Status string `json:"status"`
	}{status}})
	if err != nil {
		return fmt.Errorf("encode task control acknowledgment: %w", err)
	}
	if err := contract.ValidateCurrent("mq", body); err != nil {
		return fmt.Errorf("task control acknowledgment violates MQ contract: %w", err)
	}
	var oldType string
	var oldBody []byte
	err = tx.QueryRow(`SELECT event_type,body FROM dispatcher_outbox WHERE dispatcher_id=? AND event_id=?`, dispatcherID, eventID).Scan(&oldType, &oldBody)
	if errors.Is(err, sql.ErrNoRows) {
		if _, err := tx.Exec(`INSERT INTO dispatcher_outbox(dispatcher_id,event_id,event_type,routing_key,body) VALUES(?,?,?,?,?)`, dispatcherID, eventID, "task.control", route.BindingKey, body); err != nil {
			return fmt.Errorf("persist task control outbox: %w", err)
		}
		return nil
	}
	if err != nil {
		return fmt.Errorf("inspect existing task control outbox: %w", err)
	}
	if oldType != "task.control" || string(oldBody) != string(body) {
		return fmt.Errorf("control event identity %q conflicts with another outbound result", eventID)
	}
	if _, err := tx.Exec(`UPDATE dispatcher_outbox SET confirmed=0,confirmed_at=NULL WHERE dispatcher_id=? AND event_id=?`, dispatcherID, eventID); err != nil {
		return fmt.Errorf("requeue repeated control acknowledgment: %w", err)
	}
	return nil
}