package controller

import (
	"encoding/json"
	"io"
	"net/http"
	"strconv"
	"strings"
	"sync/atomic"
	"time"

	"github.com/mhsanaei/3x-ui/v3/internal/logger"
	"github.com/mhsanaei/3x-ui/v3/internal/web/service"
	"github.com/mhsanaei/3x-ui/v3/internal/web/service/probe"
	"github.com/mhsanaei/3x-ui/v3/internal/web/session"

	"github.com/gin-gonic/gin"
	ws "github.com/gorilla/websocket"
)

// Item 7 B3: the public status surface — the monitor hub's contract
// API, hosted by the panel process itself at the engine ROOT (outside
// the panel's secret basePath, or themes' root-relative /api calls
// could never reach it; ITEM7-SCOPE §5.5). Field shapes follow hub
// src/api.rs exactly: the five endpoints' payloads are the bare
// contract JSON, NOT the panel's Msg envelope.
//
// Audience discipline mirrors the hub: a request is "authed" (admin
// rendering) when it carries a live panel session; anonymous callers
// see only public=1 nodes and only while the public page is on, and
// no rendering ever carries ip/hostname/remark/token material.

// historySlots bounds concurrent history builds (hub HISTORY_GATE=4):
// refused, not queued, once full.
var historySlots = make(chan struct{}, 4)

// publicStreams counts open anonymous /api/ws streams (hub
// PUBLIC_STREAMS=1000); admin streams are not counted.
var publicStreams atomic.Int64

const maxThemeConfigBytes = 64 * 1024

type PublicProbeController struct {
	upgrader ws.Upgrader
}

// NewPublicProbeController registers the contract routes on the
// engine root and returns the controller (web.go also calls its
// HandleFallback from the engine's NoRoute).
func NewPublicProbeController(engine *gin.Engine) *PublicProbeController {
	pc := &PublicProbeController{
		upgrader: ws.Upgrader{
			ReadBufferSize:  4096,
			WriteBufferSize: 4096,
			// Session trust for the stream is decided per tick from
			// the panel session, not from Origin; the hub accepts
			// any origin for the anonymous audience by design.
			CheckOrigin: func(r *http.Request) bool { return true },
		},
	}
	engine.GET("/api/me", pc.me)
	engine.GET("/api/nodes", pc.nodes)
	engine.GET("/api/nodes/:id/metrics", pc.nodeMetrics)
	engine.GET("/api/ws", pc.liveWS)
	engine.GET("/api/themes/:short/config", pc.themeConfig)
	engine.PUT("/api/themes/:short/config", pc.saveThemeConfig)
	return pc
}

func probeAuthed(c *gin.Context) bool {
	return session.IsLogin(c)
}

// fromOtherOrigin mirrors hub from_other_origin: a browser request
// whose Sec-Fetch-Site is present and not "same-origin" did not come
// from this panel's own pages (a sibling subdomain is same-site but
// not same-origin, and a WebSocket is not held back by CORS).
func fromOtherOrigin(c *gin.Context) bool {
	site := c.GetHeader("Sec-Fetch-Site")
	return site != "" && site != "same-origin"
}

func answerText(c *gin.Context, status int, text string) {
	c.String(status, "%s", text)
}

func (pc *PublicProbeController) me(c *gin.Context) {
	c.JSON(http.StatusOK, struct {
		Authed      bool   `json:"authed"`
		GitHub      bool   `json:"github"`
		SiteName    string `json:"site_name"`
		PublicPage  bool   `json:"public_page"`
		HistoryDays int64  `json:"history_days"`
		Site        string `json:"site"`
	}{
		Authed:      probeAuthed(c),
		GitHub:      service.ProbeGitHubConfigured(),
		SiteName:    service.ProbeSiteName(),
		PublicPage:  service.ProbePublicPageEnabled(),
		HistoryDays: probe.RetentionDays(),
		Site:        service.ProbeSiteURL(),
	})
}

func (pc *PublicProbeController) nodes(c *gin.Context) {
	full := probeAuthed(c)
	if !full && !service.ProbePublicPageEnabled() {
		answerText(c, http.StatusUnauthorized, "需要登录后查看")
		return
	}
	if full {
		// The admin frame carries every node's addresses and private
		// notes; keep it out of every cache (hub discipline).
		c.Header("Cache-Control", "no-store, no-transform")
	}
	// The engine's gzip middleware compresses for clients that accept
	// it; the body is the shared snapshot frame either way.
	c.Data(http.StatusOK, "application/json", service.ProbeSnapshotJSON(full))
}

type metricsResponse struct {
	Metrics []probe.MetricRow  `json:"metrics"`
	Ping    []probe.PingRow    `json:"ping"`
	Probes  map[string]string  `json:"probes"`
	Loss    map[string]float64 `json:"loss"`
	Step    int64              `json:"step"`
}

func (pc *PublicProbeController) nodeMetrics(c *gin.Context) {
	id, err := strconv.ParseInt(c.Param("id"), 10, 64)
	if err != nil {
		answerText(c, http.StatusBadRequest, "请求格式不对")
		return
	}
	full := probeAuthed(c)
	if !service.ProbeNodeReadable(full, id) {
		answerText(c, http.StatusUnauthorized, "需要登录后查看")
		return
	}
	select {
	case historySlots <- struct{}{}:
		defer func() { <-historySlots }()
	default:
		answerText(c, http.StatusServiceUnavailable, "查询历史的请求太多，稍后再试")
		return
	}

	hours := int64(6)
	if raw := c.Query("hours"); raw != "" {
		h, perr := strconv.ParseInt(raw, 10, 64)
		if perr != nil {
			answerText(c, http.StatusBadRequest, "请求格式不对")
			return
		}
		hours = h
	}
	if max := probe.RetentionDays() * 24; hours < 1 {
		hours = 1
	} else if hours > max {
		hours = max
	}
	var points *int64
	if raw := c.Query("points"); raw != "" {
		p, perr := strconv.ParseInt(raw, 10, 64)
		if perr != nil {
			answerText(c, http.StatusBadRequest, "请求格式不对")
			return
		}
		points = &p
	}
	series := c.Query("series")
	wantMetrics := series == "" || series == "metrics"
	wantPing := series == "" || series == "ping"

	span := probe.ComputeSpan(hours, points, time.Now().Unix())
	resp := metricsResponse{
		Metrics: []probe.MetricRow{},
		Ping:    []probe.PingRow{},
		Probes:  map[string]string{},
		Loss:    map[string]float64{},
		Step:    span.Step,
	}
	if wantMetrics {
		rows, err := probe.MetricHistory(id, span)
		if err != nil {
			logger.Warningf("probe public: metrics %d: %v", id, err)
			answerText(c, http.StatusInternalServerError, "服务内部出错")
			return
		}
		resp.Metrics = rows
	}
	if wantPing {
		// B4: the real latency series over the same window/bucket as
		// the metrics above (hub metrics handler series=ping).
		pingRows, pingLoss, err := probe.PingHistory(id, span)
		if err != nil {
			logger.Warningf("probe public: ping %d: %v", id, err)
			answerText(c, http.StatusInternalServerError, "服务内部出错")
			return
		}
		names, err := probe.PingTaskNames(id)
		if err != nil {
			logger.Warningf("probe public: ping names %d: %v", id, err)
			answerText(c, http.StatusInternalServerError, "服务内部出错")
			return
		}
		resp.Ping = pingRows
		resp.Probes = names
		resp.Loss = pingLoss
	}
	c.JSON(http.StatusOK, resp)
}

// liveWS is the hub's browser stream: a snapshot frame on the
// operator's fast-report cadence (V2.0.2; the hub's fixed 2 s tick
// made a 1 s agent cadence invisible up front), text by default,
// binary gzip frames for the anonymous audience when opened with
// ?gzip. Audience eligibility is re-checked every tick — a socket
// outlives both the session and the public-page switch.
func (pc *PublicProbeController) liveWS(c *gin.Context) {
	authed := probeAuthed(c) && !fromOtherOrigin(c)
	if !authed && !service.ProbePublicPageEnabled() {
		answerText(c, http.StatusUnauthorized, "需要登录后查看")
		return
	}
	counted := !authed
	if counted {
		if publicStreams.Add(1) > 1000 {
			publicStreams.Add(-1)
			answerText(c, http.StatusServiceUnavailable, "同时在线的访客太多，请稍后再试")
			return
		}
		defer publicStreams.Add(-1)
	}
	_, gzipWanted := c.GetQuery("gzip")

	conn, err := pc.upgrader.Upgrade(c.Writer, c.Request, nil)
	if err != nil {
		return
	}
	defer conn.Close()
	// The browser sends nothing but the close handshake; cap frames
	// at the hub's 64 KiB anyway so a rogue peer cannot make the read
	// pump buffer without bound.
	conn.SetReadLimit(64 * 1024)

	done := make(chan struct{})
	go func() {
		defer close(done)
		for {
			if _, _, err := conn.ReadMessage(); err != nil {
				return
			}
		}
	}()

	send := func() bool {
		// Audience re-check (hub stream_audience): the admin frame is
		// sent only while the session that opened it is still live;
		// the public frame only while the page stays open. The
		// stream closes rather than downgrading.
		if authed {
			if !probeAuthed(c) {
				return false
			}
		} else if !service.ProbePublicPageEnabled() {
			return false
		}
		var frameType int
		var frame []byte
		if gzipWanted && !authed {
			frameType = ws.BinaryMessage
			frame = service.ProbeSnapshotGzip()
		} else if authed {
			frameType = ws.TextMessage
			frame = service.ProbeSnapshotJSON(true)
		} else {
			frameType = ws.TextMessage
			frame = service.ProbeSnapshotJSON(false)
		}
		_ = conn.SetWriteDeadline(time.Now().Add(10 * time.Second))
		return conn.WriteMessage(frameType, frame) == nil
	}

	// The first frame goes out immediately; later frames follow the
	// fast-report cadence, re-read after every frame so a settings
	// change lands on a live socket without a reconnect.
	if !send() {
		return
	}
	for {
		timer := time.NewTimer(time.Duration(service.ProbeFastIntervalSec()) * time.Second)
		select {
		case <-done:
			timer.Stop()
			return
		case <-timer.C:
			if !send() {
				return
			}
		}
	}
}

func (pc *PublicProbeController) themeConfig(c *gin.Context) {
	if !probeAuthed(c) && !service.ProbePublicPageEnabled() {
		answerText(c, http.StatusUnauthorized, "需要登录后查看")
		return
	}
	short := c.Param("short")
	if !service.ValidThemeShort(short) {
		answerText(c, http.StatusNotFound, "请求的内容不存在")
		return
	}
	raw, err := service.ProbeThemeConfigValue(short)
	if err != nil {
		logger.Warningf("probe public: theme config %s: %v", short, err)
		answerText(c, http.StatusInternalServerError, "服务内部出错")
		return
	}
	c.Data(http.StatusOK, "application/json", []byte(raw))
}

func (pc *PublicProbeController) saveThemeConfig(c *gin.Context) {
	if !probeAuthed(c) {
		answerText(c, http.StatusUnauthorized, "登录已失效，请重新登录")
		return
	}
	if fromOtherOrigin(c) {
		answerText(c, http.StatusForbidden, "请求来自其他网站，已拒绝")
		return
	}
	short := c.Param("short")
	// Hub save_theme_config gates on selectable, not on a disk copy:
	// the built-in theme's config is savable before any install.
	if !service.ValidThemeShort(short) || !service.ProbeThemeSelectable(short) {
		answerText(c, http.StatusBadRequest, "主题没有安装")
		return
	}
	body, err := io.ReadAll(io.LimitReader(c.Request.Body, maxThemeConfigBytes+1))
	if err != nil {
		answerText(c, http.StatusBadRequest, "请求格式不对")
		return
	}
	if len(body) > maxThemeConfigBytes {
		answerText(c, http.StatusRequestEntityTooLarge, "提交的内容过大")
		return
	}
	var obj map[string]json.RawMessage
	if err := json.Unmarshal(body, &obj); err != nil || obj == nil {
		answerText(c, http.StatusBadRequest, "请求格式不对")
		return
	}
	if err := service.SaveProbeThemeConfigRaw(short, string(body)); err != nil {
		logger.Warningf("probe public: save theme config %s: %v", short, err)
		answerText(c, http.StatusInternalServerError, "服务内部出错")
		return
	}
	c.Status(http.StatusNoContent)
}

// HandleFallback serves the public theme from the engine's NoRoute:
// unknown /api/* paths answer the hub's API 404, everything outside
// the panel basePath falls to the current theme's dist (SPA fallback
// inside). Returns false when the request is the panel's own (its
// SPA fallback decides) or when no theme is installed to answer.
func (pc *PublicProbeController) HandleFallback(c *gin.Context) bool {
	if c.Request.Method != http.MethodGet && c.Request.Method != http.MethodHead {
		return false
	}
	path := c.Request.URL.Path
	if path == "/api" || strings.HasPrefix(path, "/api/") {
		answerText(c, http.StatusNotFound, "没有这个接口："+path)
		return true
	}
	basePath, _ := c.Get("base_path")
	if bp, ok := basePath.(string); ok && bp != "" && bp != "/" {
		if strings.HasPrefix(path, bp) {
			return false
		}
	} else if strings.HasPrefix(path, "/panel") || strings.HasPrefix(path, "/assets") {
		return false
	}
	// V2.0.1 ③: with the public page switched off, the theme shell
	// is not public content — an anonymous visitor gets a plain 404
	// (the pre-item-7 behaviour for the root path), never the shell
	// whose "public page off" redirect chain dead-ends on /admin.
	// A logged-in operator still reaches the theme (preview, theme
	// config edits), exactly like the data APIs' own gate.
	if !service.ProbePublicPageEnabled() && !probeAuthed(c) {
		answerText(c, http.StatusNotFound, "404 page not found")
		return true
	}
	return service.ServeProbeThemePath(c, strings.TrimPrefix(path, "/"))
}