// P0/PRF Registration API
// Stores wrapped L3 credentials in admin DB for POP distribution

package main

import (
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net/http"
	"strconv"
	"time"
)

// CredentialRegisterRequest - what the client sends when enrolling a device
type CredentialRegisterRequest struct {
	// Identity
	CustomerID string `json:"customer_id"` // Who owns this credential
	VaultL0    string `json:"vault_l0"`    // Which vault this opens

	// WebAuthn data
	CredentialID string `json:"credential_id"` // base64 encoded WebAuthn credential ID
	PublicKey    string `json:"public_key"`    // base64 encoded public key (for signature verification)

	// PRF/P0 data
	P0      string `json:"p0"`       // First 4 bytes of PRF, hex encoded (lookup key)
	PRFSalt string `json:"prf_salt"` // Salt used for PRF (should be "Clavitor")

	// Wrapped L3 (the actual vault key, encrypted with PRF)
	WrappedL3 string `json:"wrapped_l3"` // base64 encoded encrypted L3

	// Metadata
	EnrolledBy string `json:"enrolled_by"` // Human ID who authorized this (if adding 2nd device)
	DeviceName string `json:"device_name"` // "YubiKey 5", "iPhone Touch ID", etc.
	DeviceType string `json:"device_type"` // "cross-platform", "platform", "hybrid"
}

// CredentialRegisterResponse
type CredentialRegisterResponse struct {
	Success      bool   `json:"success"`
	CredentialID int64  `json:"credential_id,omitempty"` // Our internal ID
	Error        string `json:"error,omitempty"`
}

// RegisterCredential stores a new P0→WL3 mapping
func handleRegisterCredential(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	var req CredentialRegisterRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		respondJSON(w, CredentialRegisterResponse{Success: false, Error: "invalid json: " + err.Error()})
		return
	}

	// Validate required fields
	if req.CustomerID == "" || req.VaultL0 == "" || req.P0 == "" || req.WrappedL3 == "" {
		respondJSON(w, CredentialRegisterResponse{Success: false, Error: "missing required fields"})
		return
	}

	// Verify customer exists
	var customerExists bool
	err := db.QueryRow("SELECT 1 FROM customers WHERE id = ?", req.CustomerID).Scan(&customerExists)
	if err != nil {
		respondJSON(w, CredentialRegisterResponse{Success: false, Error: "customer not found"})
		return
	}

	// Check for P0 collision (should be rare but possible)
	var existingL0 string
	err = db.QueryRow("SELECT l0 FROM credentials WHERE p0 = ?", req.P0).Scan(&existingL0)
	if err == nil && existingL0 != req.VaultL0 {
		// P0 collision with different vault - this is a problem
		respondJSON(w, CredentialRegisterResponse{Success: false, Error: "P0 collision detected - different vault"})
		return
	}

	// Generate WL3 storage path
	// Format: {first_2_chars_of_p0}/{full_p0}/{timestamp}_{random}.cla
	wl3Path := generateWL3Path(req.P0)

	// Generate our internal credential ID
	credID := generateInternalID()

	// Store in DB
	_, err = db.Exec(`
		INSERT INTO credentials (
			id, customer_id, p0, l0, credential_id, public_key,
			wl3_path, enrolled_by, device_name, device_type,
			created_at, last_used_at
		) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
	`,
		credID,
		req.CustomerID,
		req.P0,
		req.VaultL0,
		req.CredentialID, // Store original WebAuthn credential ID
		req.PublicKey,
		wl3Path,
		req.EnrolledBy,
		req.DeviceName,
		req.DeviceType,
		time.Now().Unix(),
		time.Now().Unix(),
	)

	if err != nil {
		respondJSON(w, CredentialRegisterResponse{Success: false, Error: "database error: " + err.Error()})
		return
	}

	// Store the actual wrapped L3 content
	// In production this would write to the WORM filesystem
	// For now we store it in a separate table or as a blob
	wrappedL3Bytes, _ := base64.StdEncoding.DecodeString(req.WrappedL3)
	err = storeWL3Content(wl3Path, wrappedL3Bytes)
	if err != nil {
		// Rollback credential record
		db.Exec("DELETE FROM credentials WHERE id = ?", credID)
		respondJSON(w, CredentialRegisterResponse{Success: false, Error: "failed to store WL3: " + err.Error()})
		return
	}

	// Log the event
	logEvent("credential_registered", req.CustomerID, req.VaultL0, map[string]interface{}{
		"credential_id": credID,
		"p0":            req.P0,
		"device_name":   req.DeviceName,
	})

	respondJSON(w, CredentialRegisterResponse{Success: true, CredentialID: credID})
}

// ListCredentialsForCustomer - returns all credentials for a customer
// Used by POPs to pull WL3s for their assigned customers
func handleListCredentials(w http.ResponseWriter, r *http.Request) {
	customerID := r.URL.Query().Get("customer_id")
	if customerID == "" {
		http.Error(w, "customer_id required", http.StatusBadRequest)
		return
	}

	// TODO: Authenticate POP - must have valid agent token
	// For now open for Q&D

	rows, err := db.Query(`
		SELECT id, p0, l0, wl3_path, device_name, device_type, created_at
		FROM credentials
		WHERE customer_id = ?
		ORDER BY created_at DESC
	`, customerID)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	defer rows.Close()

	var creds []map[string]interface{}
	for rows.Next() {
		var id, p0, l0, path, deviceName, deviceType string
		var createdAt int64
		rows.Scan(&id, &p0, &l0, &path, &deviceName, &deviceType, &createdAt)
		creds = append(creds, map[string]interface{}{
			"id":          id,
			"p0":          p0,
			"l0":          l0,
			"wl3_path":    path,
			"device_name": deviceName,
			"device_type": deviceType,
			"created_at":  createdAt,
		})
	}

	respondJSON(w, creds)
}

// GetWL3Content - returns the actual wrapped L3 bytes
// POPs call this to download WL3 for local storage
func handleGetWL3(w http.ResponseWriter, r *http.Request) {
	p0 := r.URL.Query().Get("p0")
	if p0 == "" {
		http.Error(w, "p0 required", http.StatusBadRequest)
		return
	}

	// TODO: Authenticate POP with super duper secure auth
	// For now just return the content

	// Find the WL3 path
	var wl3Path string
	err := db.QueryRow("SELECT wl3_path FROM credentials WHERE p0 = ? ORDER BY created_at DESC LIMIT 1", p0).Scan(&wl3Path)
	if err != nil {
		http.Error(w, "credential not found", http.StatusNotFound)
		return
	}

	// Read and return
	content, err := readWL3Content(wl3Path)
	if err != nil {
		http.Error(w, "failed to read WL3: "+err.Error(), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/octet-stream")
	w.Write(content)
}

// SyncStatus - returns credentials that need syncing to POPs
// POPs poll this to know what to download
func handleSyncStatus(w http.ResponseWriter, r *http.Request) {
	// Query params
	popID := r.URL.Query().Get("pop_id")
	lastSync := r.URL.Query().Get("last_sync")

	if popID == "" {
		http.Error(w, "pop_id required", http.StatusBadRequest)
		return
	}

	// TODO: Authenticate POP

	var lastSyncTime int64
	if lastSync != "" {
		lastSyncTime, _ = strconv.ParseInt(lastSync, 10, 64)
	}

	// Return credentials created since last sync
	rows, err := db.Query(`
		SELECT id, customer_id, p0, l0, wl3_path, created_at
		FROM credentials
		WHERE created_at > ?
		ORDER BY created_at ASC
		LIMIT 1000
	`, lastSyncTime)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	defer rows.Close()

	var toSync []map[string]interface{}
	for rows.Next() {
		var id, customerID, p0, l0, path string
		var createdAt int64
		rows.Scan(&id, &customerID, &p0, &l0, &path, &createdAt)
		toSync = append(toSync, map[string]interface{}{
			"id":          id,
			"customer_id": customerID,
			"p0":          p0,
			"l0":          l0,
			"wl3_path":    path,
			"created_at":  createdAt,
		})
	}

	// Update POP sync state
	_, _ = db.Exec(`
		INSERT INTO pop_sync_state (pop_id, last_sync_at, updated_at)
		VALUES (?, ?, ?)
		ON CONFLICT(pop_id) DO UPDATE SET
			last_sync_at = excluded.last_sync_at,
			updated_at = excluded.updated_at
	`, popID, time.Now().Unix(), time.Now().Unix())

	respondJSON(w, map[string]interface{}{
		"credentials": toSync,
		"server_time": time.Now().Unix(),
	})
}

// TODO: SUPER DUPER SECURE POP AUTHENTICATION
// This needs:
// 1. mTLS - POP presents certificate signed by our CA
// 2. Signed requests - each request signed with POP's private key
// 3. Replay protection - nonce + timestamp
// 4. IP allowlist - only known POP IPs
// 5. Rate limiting per POP
// 6. Audit logging of all POP access

func handlePOPAuthMiddleware(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		// TODO: Implement super duper secure auth
		// For now just pass through for Q&D
		next(w, r)
	}
}

// Helper functions

func generateWL3Path(p0 string) string {
	// P0 is hex, like "a1b2c3d4"
	// Path: a1/a1b2c3d4/20250405_7a8f9e2b.cla
	if len(p0) < 4 {
		p0 = fmt.Sprintf("%08s", p0) // Pad
	}

	shard := p0[:2] // First 2 chars for sharding
	now := time.Now()
	random := generateRandomHex(8)

	return fmt.Sprintf("%s/%s/%04d%02d%02d_%s.cla",
		shard, p0, now.Year(), now.Month(), now.Day(), random)
}

func generateInternalID() int64 {
	// Use timestamp + random for now
	// In production use lib.NewID()
	return time.Now().UnixNano()
}

func generateRandomHex(n int) string {
	bytes := make([]byte, n/2)
	// In real code: crypto/rand
	for i := range bytes {
		bytes[i] = byte(i) // Fake
	}
	return fmt.Sprintf("%x", bytes)
}

func storeWL3Content(path string, content []byte) error {
	// TODO: Write to WORM filesystem
	// For now store in a simple table
	_, err := db.Exec(`
		INSERT OR REPLACE INTO wl3_storage (path, content, created_at)
		VALUES (?, ?, ?)
	`, path, content, time.Now().Unix())
	return err
}

func readWL3Content(path string) ([]byte, error) {
	// TODO: Read from WORM filesystem
	// For now read from table
	var content []byte
	err := db.QueryRow("SELECT content FROM wl3_storage WHERE path = ?", path).Scan(&content)
	return content, err
}

func logEvent(eventType, customerID, vaultL0 string, details map[string]interface{}) {
	detailsJSON, _ := json.Marshal(details)
	db.Exec(`
		INSERT INTO events (occurred_at, event_type, entity_type, entity_id, customer_id, details, source)
		VALUES (?, ?, ?, ?, ?, ?, ?)
	`, time.Now().Unix(), eventType, "credential", "", customerID, string(detailsJSON), "api")
}