// Command bat-api is the resource bootstrap and distribution HTTP service for BlueArchiveToolkit.
//
// Responsibility boundary:
//   - bat (Rust): official resource auto-discover, pull, verify, publish, daemon RPC
//   - bat-api (Go): startup resource bootstrap, server-info rewrite,
//     read-only distribution of published resources (CDN-shaped paths), release
//     inspection APIs, and normal process configuration (.env / flags for listen
//     port, RPC socket, reserved database/redis settings)
//
// bat-api discovers and periodically refreshes the current release through the
// bat.sock JSON-RPC contract (daemon.status first, then daemon.doctor, then
// catalog/resource methods). The production resource root comes from RPC; the
// resource-root override is for local fixtures or emergency diagnostics.
package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"path/filepath"
	"strings"
	"syscall"
	"time"

	"bat-api/internal/api"
	"bat-api/internal/backendrpc"
)

func main() {
	log.SetFlags(log.LstdFlags | log.Lmsgprefix)
	log.SetPrefix("bat-api ")

	cfg := api.DefaultConfig()
	if os.Getenv("BAT_API_SKIP_ENV_FILE") != "1" {
		envPath := envFilePath()
		if err := ensureEnvTemplate(envPath); err != nil {
			log.Printf("warn: env template: %v", err)
		}
		if err := api.LoadEnvFile(envPath); err != nil {
			log.Fatalf("load .env: %v", err)
		}
	}
	api.ApplyEnv(&cfg)

	listen := flag.String("listen", cfg.Listen, "HTTP listen address")
	publicBase := flag.String("public-base-url", cfg.PublicBaseURL, "public base URL for Addressables rewrite")
	stateDir := flag.String("state-dir", cfg.StateDir, "bat daemon state dir (derives default socket)")
	socket := flag.String("socket", cfg.SocketPath, "path to bat.sock JSON-RPC socket (primary discovery)")
	resourceRoot := flag.String("resource-root", cfg.ResourceRoot, "override published release root (tests/emergency)")
	serverInfo := flag.String("server-info-file", cfg.ServerInfoFile, "optional server-info JSON path")
	requireIndexed := flag.Bool("require-indexed", cfg.RequireIndexed, "only serve files present in the release index")
	verifySize := flag.Bool("verify-size", cfg.VerifySize, "reject CDN files whose size differs from the index")
	rpcTimeout := flag.Duration("rpc-timeout", cfg.RPCTimeout, "daemon RPC timeout")
	refreshInterval := flag.Duration("refresh-interval", cfg.RefreshInterval, "periodic release discovery interval (0 disables)")
	authQueryParam := flag.String("auth-query-param", cfg.AuthQueryParam, "query parameter accepted for token auth fallback")
	authExemptPaths := flag.String("auth-exempt-paths", strings.Join(cfg.AuthExemptPaths, ","), "comma-separated auth-exempt exact paths or slash-prefixes")
	trustProxyHeaders := flag.Bool("trust-proxy-headers", cfg.TrustProxyHeaders, "trust X-Forwarded-For and X-Real-IP from reverse proxy")
	accessLog := flag.Bool("access-log", cfg.AccessLog, "enable per-request access logs without query strings")
	rateLimitRPS := flag.Float64("rate-limit-rps", cfg.RateLimitRPS, "per-client request rate limit; 0 disables")
	rateLimitBurst := flag.Int("rate-limit-burst", cfg.RateLimitBurst, "per-client rate limit burst")
	maxResourceLimit := flag.Int("max-resource-limit", cfg.MaxResourcePageLimit, "maximum /v1/resources page size")
	flag.Parse()

	cfg.Listen = *listen
	cfg.PublicBaseURL = *publicBase
	cfg.StateDir = *stateDir
	cfg.SocketPath = *socket
	cfg.ResourceRoot = *resourceRoot
	cfg.ServerInfoFile = *serverInfo
	cfg.RequireIndexed = *requireIndexed
	cfg.VerifySize = *verifySize
	cfg.RPCTimeout = *rpcTimeout
	cfg.RefreshInterval = *refreshInterval
	cfg.AuthQueryParam = *authQueryParam
	cfg.AuthExemptPaths = splitFlagCSV(*authExemptPaths)
	cfg.TrustProxyHeaders = *trustProxyHeaders
	cfg.AccessLog = *accessLog
	cfg.RateLimitRPS = *rateLimitRPS
	cfg.RateLimitBurst = *rateLimitBurst
	cfg.MaxResourcePageLimit = *maxResourceLimit
	// If socket still empty after flags, derive from state-dir.
	if cfg.SocketPath == "" {
		cfg.SocketPath = filepath.Join(cfg.StateDir, "bat.sock")
	}
	if err := cfg.Normalize(); err != nil {
		log.Fatalf("config: %v", err)
	}

	var backend api.Backend
	client := backendrpc.New(cfg.SocketPath)
	client.Timeout = cfg.RPCTimeout
	backend = api.RPCClient{Client: client}

	server := api.NewServer(cfg, backend, log.Default())
	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer cancel()

	refreshCtx, refreshCancel := context.WithTimeout(ctx, cfg.RPCTimeout+5*time.Second)
	if err := server.Refresh(refreshCtx); err != nil {
		log.Printf("initial discover failed: %v (serving with empty/partial index)", err)
	}
	refreshCancel()
	server.StartRefreshLoop(ctx)

	if err := server.ListenAndServe(ctx); err != nil && err != context.Canceled {
		log.Fatalf("serve: %v", err)
	}
}

func envFilePath() string {
	exe, err := os.Executable()
	if err != nil {
		return api.EnvFileName
	}
	return filepath.Join(filepath.Dir(exe), api.EnvFileName)
}

func ensureEnvTemplate(path string) error {
	if _, err := os.Stat(path); err == nil {
		return nil
	} else if !os.IsNotExist(err) {
		return err
	}
	if err := os.WriteFile(path, []byte(api.EnvTemplate), 0o600); err != nil {
		return fmt.Errorf("write %s: %w", path, err)
	}
	log.Printf("wrote config template %s", path)
	return nil
}

func splitFlagCSV(raw string) []string {
	var out []string
	for _, part := range strings.Split(raw, ",") {
		part = strings.TrimSpace(part)
		if part != "" {
			out = append(out, part)
		}
	}
	return out
}