// health.go implements the optional flyto.HealthChecker capability for
// OpenAI-compatible endpoints that expose a liveness route (oMLX: GET
// /health, no auth, {"status":"healthy",...}). Real OpenAI has no such
// endpoint -- Config.HealthCheckPath stays empty there and CheckHealth is a
// no-op nil, so the capability never misreports a healthy cloud endpoint as
// down.
//
// health.go 为暴露存活路由的 OpenAI 兼容端点 (oMLX: GET /health, 免鉴权,
// {"status":"healthy",...}) 实现可选 flyto.HealthChecker 能力. 真 OpenAI 无此
// 端点 -- 其 Config.HealthCheckPath 留空, CheckHealth 为 no-op nil, 该能力
// 绝不把健康的云端端点误报为挂.

package openai

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"git.flytoex.net/yuanwei/flyto-agent/core/pkg/flyto"
)

// Provider satisfies the shared flyto.HealthChecker capability.
var _ flyto.HealthChecker = (*Provider)(nil)

// healthProbeTimeout bounds the liveness GET independently of the caller's
// (long, transcription-sized) deadline: a probe against a sleeping Mac should
// answer "offline" in seconds, not inherit a minutes-long budget.
//
// healthProbeTimeout 独立限探活 GET, 不吃调用方 (给转写准备的分钟级) deadline:
// 对睡着的 Mac 探活应秒级报 "离线", 不继承分钟级预算.
const healthProbeTimeout = 5 * time.Second

// CheckHealth implements flyto.HealthChecker. No-op nil when
// Config.HealthCheckPath is empty (no probe available != unhealthy). A
// reachable endpoint must answer 2xx AND, when the body carries a "status"
// field, report a healthy value -- {"status":"degraded"} with HTTP 200 is
// still a failure (fail-loud, ADR-0006). Both "healthy" (single-backend oMLX)
// and "ok" (oMLX multi-backend router since 2026-07) count as healthy: the
// router's top-level status is {"status":"ok","backends":{...}}, and
// rejecting it silently forced every transcription onto the cloud fallback
// (prod incident 2026-07-17..19).
//
// CheckHealth 实现 flyto.HealthChecker. Config.HealthCheckPath 空时 no-op nil
// (无探测可用 != 不健康). 可达端点须 2xx **且** body 带 "status" 字段时报健康值
// -- HTTP 200 + {"status":"degraded"} 仍算失败 (fail-loud, ADR-0006).
// "healthy" (单后端 oMLX) 与 "ok" (2026-07 起的 oMLX 多后端 router, 顶层
// {"status":"ok","backends":{...}}) 都算健康 -- 拒掉 "ok" 曾把所有转写
// 静默逼上云端降级 (生产事故 2026-07-17..19).
func (p *Provider) CheckHealth(ctx context.Context) error {
	if p.cfg.HealthCheckPath == "" {
		return nil
	}
	ctx, cancel := context.WithTimeout(ctx, healthProbeTimeout)
	defer cancel()

	url := strings.TrimSuffix(p.cfg.BaseURL, "/") + p.cfg.HealthCheckPath
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return fmt.Errorf("openai: new health request: %w", err)
	}
	resp, err := p.visionHTTPClient().Do(httpReq)
	if err != nil {
		return fmt.Errorf("openai: backend health probe failed (offline?): %w", err)
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
	if resp.StatusCode/100 != 2 {
		return fmt.Errorf("openai: backend unhealthy: status %d: %s", resp.StatusCode, visionSnippet(body, 200))
	}
	var h struct {
		Status string `json:"status"`
	}
	if err := json.Unmarshal(body, &h); err == nil && h.Status != "" && h.Status != "healthy" && h.Status != "ok" {
		return fmt.Errorf("openai: backend reports status %q (want healthy/ok)", h.Status)
	}
	return nil
}