package postgres

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/jackc/pgx/v5"

	"knowledge-governance/internal/libraryexecutor"
)

// 为什么落库而不是 API 直接探测：agent socket 只挂在 worker 容器里，API 那个
// LIBRARY_AGENT_SOCKET 即使配了也 dial 不到。谁真能执行就由谁观测，页面读结果。
const executorStatusColumns = `instance, reachable, busy, degraded, identity, status_error, observed_at`

// UpsertLibraryExecutorStatus 记录一次真实探测。降级/不可达同样要写：
// "最新一次观测是什么"比"最后一条好消息"更有用。
func (s *Store) UpsertLibraryExecutorStatus(ctx context.Context, observation libraryexecutor.Observation, observer string, now time.Time) error {
	identity, err := json.Marshal(observation.Identity)
	if err != nil {
		return fmt.Errorf("encode library executor identity: %w", err)
	}
	if observation.Instance == "" {
		return errors.New("library executor observation needs an instance")
	}
	observedAt := observation.ObservedAt
	if observedAt.IsZero() {
		observedAt = now
	}
	_, err = s.db.Exec(ctx, `
INSERT INTO library_executor_status (instance, reachable, busy, degraded, identity, status_error, observer, observed_at)
VALUES ($1,$2,$3,$4,$5::jsonb,$6,$7,$8)
ON CONFLICT (instance) DO UPDATE SET
    reachable = EXCLUDED.reachable,
    busy = EXCLUDED.busy,
    degraded = EXCLUDED.degraded,
    identity = EXCLUDED.identity,
    status_error = EXCLUDED.status_error,
    observer = EXCLUDED.observer,
    observed_at = EXCLUDED.observed_at`,
		observation.Instance, observation.Reachable, observation.Busy, observation.Degraded,
		string(identity), observation.Error, observer, observedAt.UTC())
	if err != nil {
		return fmt.Errorf("record library executor status: %w", err)
	}
	return nil
}

// LibraryExecutorStatus 读某个实例最近一次观测；没有记录返回 nil（不是"可用"）。
func (s *Store) LibraryExecutorStatus(ctx context.Context, instance string) (*libraryexecutor.Observation, error) {
	row := s.db.QueryRow(ctx, `SELECT `+executorStatusColumns+` FROM library_executor_status WHERE instance=$1`, instance)
	var observation libraryexecutor.Observation
	var raw []byte
	err := row.Scan(&observation.Instance, &observation.Reachable, &observation.Busy, &observation.Degraded,
		&raw, &observation.Error, &observation.ObservedAt)
	if errors.Is(err, pgx.ErrNoRows) {
		return nil, nil
	}
	if err != nil {
		return nil, fmt.Errorf("read library executor status: %w", err)
	}
	if len(raw) > 0 {
		if err := json.Unmarshal(raw, &observation.Identity); err != nil {
			return nil, fmt.Errorf("library executor identity unreadable: %w", err)
		}
	}
	return &observation, nil
}