package handlers

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"sync"
	"time"

	"git.georgsen.dk/hwlab/internal/labels"
	"git.georgsen.dk/hwlab/internal/printer"
	"git.georgsen.dk/hwlab/internal/tester"
)

// TestNetBoxClient is the subset of netbox.Client used by TestHandler.
// Using an interface allows test injection without depending on the concrete type.
type TestNetBoxClient interface {
	CreateCable(ctx context.Context, label, assetTag, testDataJSON string) (int64, error)
}

// TestPrinter is the narrow print interface for TestHandler.
// Allows nil injection (auto-print skipped when nil).
type TestPrinter interface {
	Print(bitmap []byte, width, height int) error
}

// TestHandler handles the three cable-test endpoints:
//
//	POST /api/test/cable   — receive TestResult, persist to NetBox, auto-print
//	GET  /api/test/events  — SSE stream of LiveReading from attached StreamingTesterDriver
//	GET  /api/test/recent  — last ≤20 TestResult entries from in-memory ring buffer
//
// T-05-04: StreamEvents exits on r.Context().Done() — no goroutine leak.
// T-05-05: rate limit on print calls (1/second) inherited via printCooldown.
type TestHandler struct {
	nb      TestNetBoxClient
	printer TestPrinter // may be nil — auto-print skipped

	// ring buffer (cap ringCap, thread-safe)
	mu     sync.Mutex
	recent []tester.TestResult

	// live readings channel; set by AttachStream
	liveCh chan tester.LiveReading

	// rate limiting (T-05-05 — DoS/label-waste mitigation)
	printMu       sync.Mutex
	lastPrintTime time.Time
	printCooldown time.Duration
}

const ringCap = 20

// NewTestHandler constructs a TestHandler. p may be nil (auto-print disabled).
func NewTestHandler(nb TestNetBoxClient, p TestPrinter) *TestHandler {
	return &TestHandler{
		nb:            nb,
		printer:       p,
		recent:        make([]tester.TestResult, 0, ringCap),
		liveCh:        make(chan tester.LiveReading, 64),
		printCooldown: time.Second,
	}
}

// AttachStream wires a StreamingTesterDriver's live readings channel to the
// SSE broadcaster. Safe to call from any goroutine.
func (h *TestHandler) AttachStream(ch <-chan tester.LiveReading) {
	go func() {
		for reading := range ch {
			select {
			case h.liveCh <- reading:
			default:
				// Drop if buffer full — non-blocking, live readings are best-effort.
			}
		}
	}()
}

// cableTestRequest is the JSON body for POST /api/test/cable.
// T-05-03: unknown fields are disallowed (DisallowUnknownFields below).
type cableTestRequest struct {
	CableType     int     `json:"cable_type"`
	USBVersion    string  `json:"usb_version"`
	DPVersion     string  `json:"dp_version"`
	HDMIVersion   string  `json:"hdmi_version"`
	SpeedGbps     float64 `json:"speed_gbps"`
	MaxWatts      int     `json:"max_watts"`
	PinContinuity bool    `json:"pin_continuity"`
	HasEMarker    bool    `json:"has_emarker"`
	ResistanceOhm float64 `json:"resistance_ohm"`
	HWID          string  `json:"hw_id"`
}

// cableTestResponse is the JSON body returned by POST /api/test/cable on 201.
type cableTestResponse struct {
	HWID        string `json:"hw_id"`
	NetBoxID    int64  `json:"netbox_id"`
	PrintSkipped bool  `json:"print_skipped"`
}

// SubmitCableTest handles POST /api/test/cable.
//
// Flow:
//  1. Decode JSON body (DisallowUnknownFields — T-05-03)
//  2. Marshal TestResult to JSON for test_data custom field
//  3. Derive cable label from CableType + version strings
//  4. CreateCable in NetBox
//  5. Auto-print cable label (non-fatal; rate-limited — T-05-05)
//  6. Prepend to ring buffer (cap 20)
//  7. Return 201 cableTestResponse
func (h *TestHandler) SubmitCableTest(w http.ResponseWriter, r *http.Request) {
	var req cableTestRequest
	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()
	if err := dec.Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid JSON: " + err.Error()})
		return
	}

	// Build TestResult from request
	result := tester.TestResult{
		CableType:     tester.CableType(req.CableType),
		USBVersion:    req.USBVersion,
		DPVersion:     req.DPVersion,
		HDMIVersion:   req.HDMIVersion,
		SpeedGbps:     req.SpeedGbps,
		MaxWatts:      req.MaxWatts,
		PinContinuity: req.PinContinuity,
		HasEMarker:    req.HasEMarker,
		ResistanceOhm: req.ResistanceOhm,
	}

	// Marshal TestResult as test_data JSON for NetBox custom field
	testDataJSON, err := json.Marshal(result)
	if err != nil {
		log.Printf("test: marshal TestResult: %v", err)
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "internal error"})
		return
	}

	// Derive cable label
	cableLabel := deriveCableLabel(result)

	// Create NetBox cable record
	netboxID, err := h.nb.CreateCable(r.Context(), cableLabel, req.HWID, string(testDataJSON))
	if err != nil {
		log.Printf("test: CreateCable: %v", err)
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "NetBox error: " + err.Error()})
		return
	}

	// Auto-print cable label (non-fatal — T-05-05 rate limit applies)
	printSkipped := true
	if h.printer != nil && req.HWID != "" {
		// Rate limit: reject if last print was less than printCooldown ago (T-05-05)
		h.printMu.Lock()
		now := time.Now()
		rateLimitOK := h.lastPrintTime.IsZero() || now.Sub(h.lastPrintTime) >= h.printCooldown
		if rateLimitOK {
			h.lastPrintTime = now
		}
		h.printMu.Unlock()

		if rateLimitOK {
			labelData := labels.CableLabelData{
				HWID:         req.HWID,
				Name:         cableLabel,
				USBVersion:   req.USBVersion,
				MaxSpeedGbps: req.SpeedGbps,
				MaxWatts:     req.MaxWatts,
				TestDate:     time.Now().Format("2006-01-02"),
			}
			img, renderErr := labels.RenderCable(labelData)
			if renderErr == nil {
				bm, bw, bh := printer.ImageToRawBitmap(img)
				if printErr := h.printer.Print(bm, bw, bh); printErr == nil {
					printSkipped = false
				} else {
					log.Printf("test: auto-print error: %v", printErr)
				}
			} else {
				log.Printf("test: cable label render error: %v", renderErr)
			}
		} else {
			log.Printf("test: auto-print rate limited — skipping")
		}
	}

	// Prepend to ring buffer (most recent first, cap 20)
	h.mu.Lock()
	h.recent = append([]tester.TestResult{result}, h.recent...)
	if len(h.recent) > ringCap {
		h.recent = h.recent[:ringCap]
	}
	h.mu.Unlock()

	writeJSON(w, http.StatusCreated, cableTestResponse{
		HWID:         req.HWID,
		NetBoxID:     netboxID,
		PrintSkipped: printSkipped,
	})
}

// StreamEvents handles GET /api/test/events — SSE stream of LiveReading values.
//
// T-05-04: exits on r.Context().Done() — goroutine-leak-safe.
// Sends a 30-second keepalive comment to prevent proxy timeout.
func (h *TestHandler) StreamEvents(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("X-Accel-Buffering", "no")

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming not supported", http.StatusInternalServerError)
		return
	}

	fmt.Fprintf(w, ": connected\n\n")
	flusher.Flush()

	ticker := time.NewTicker(30 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-r.Context().Done():
			// T-05-04: client disconnected — return cleanly, no goroutine leak.
			return

		case reading, ok := <-h.liveCh:
			if !ok {
				return
			}
			data, err := json.Marshal(reading)
			if err != nil {
				fmt.Fprintf(w, ": marshal error\n\n")
				flusher.Flush()
				continue
			}
			fmt.Fprintf(w, "data: %s\n\n", data)
			flusher.Flush()

		case <-ticker.C:
			fmt.Fprintf(w, ": keepalive\n\n")
			flusher.Flush()
		}
	}
}

// RecentTests handles GET /api/test/recent — returns last ≤20 TestResult entries.
// Returns an empty JSON array when no tests have been submitted.
func (h *TestHandler) RecentTests(w http.ResponseWriter, r *http.Request) {
	h.mu.Lock()
	results := make([]tester.TestResult, len(h.recent))
	copy(results, h.recent)
	h.mu.Unlock()

	writeJSON(w, http.StatusOK, results)
}

// deriveCableLabel builds a human-readable cable label from a TestResult.
func deriveCableLabel(r tester.TestResult) string {
	switch r.CableType {
	case tester.CableTypeUSB:
		version := r.USBVersion
		if version == "" {
			version = "USB"
		}
		if r.SpeedGbps > 0 {
			return fmt.Sprintf("%s / %.0f Gbps Cable", version, r.SpeedGbps)
		}
		return version + " Cable"
	case tester.CableTypeDP:
		version := r.DPVersion
		if version == "" {
			version = "DP"
		}
		return "DisplayPort " + version + " Cable"
	case tester.CableTypeHDMI:
		version := r.HDMIVersion
		if version == "" {
			version = "HDMI"
		}
		return "HDMI " + version + " Cable"
	default:
		return "Cable"
	}
}