// kamado-api is the middleware that sits between ckpool-solo and the
// Kamado dashboard. It polls ckpool's Unix socket API, calls bitcoind
// over JSON-RPC, and serves the merged state over REST (WebSocket push,
// SQLite persistence, ZMQ and log-tailer-based block detection land in
// a follow-up commit).
package main

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"net/url"
	"os"
	"os/signal"
	"strconv"
	"strings"
	"syscall"
	"time"

	"github.com/kamadopool/kamado-api/internal/bitcoind"
	"github.com/kamadopool/kamado-api/internal/blocksubmit"
	"github.com/kamadopool/kamado-api/internal/ckpool"
	"github.com/kamadopool/kamado-api/internal/config"
	"github.com/kamadopool/kamado-api/internal/httpapi"
	"github.com/kamadopool/kamado-api/internal/logmon"
	"github.com/kamadopool/kamado-api/internal/state"
	"github.com/kamadopool/kamado-api/internal/store"
	"github.com/kamadopool/kamado-api/internal/zmqmon"
)

func main() {
	log := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{Level: slog.LevelInfo}))
	slog.SetDefault(log)

	cfg, err := config.FromEnv()
	if err != nil {
		log.Error("config", "err", err)
		os.Exit(1)
	}
	log.Info("kamado-api starting",
		"listen", cfg.ListenAddr,
		"sockdir", cfg.CKPoolSockDir,
		"bitcoind", cfg.BitcoinRPCURL,
		"poll_interval", cfg.PollInterval,
	)

	ck := ckpool.New(cfg.CKPoolSockDir)
	rpc := bitcoind.NewRPC(cfg.BitcoinRPCURL, cfg.BitcoinRPCUser, cfg.BitcoinRPCPassword, cfg.BitcoinRPCTimeout)

	// Persistent block history. Non-fatal if it can't be opened — the
	// aggregator falls back to an in-memory ring so the pool keeps
	// running even with a broken data volume.
	var blockStore *store.BlockStore
	if cfg.DBPath != "" {
		if s, err := store.Open(cfg.DBPath); err != nil {
			log.Warn("block store open failed, running without persistence", "path", cfg.DBPath, "err", err)
		} else {
			blockStore = s
			defer blockStore.Close()
			log.Info("block store opened", "path", cfg.DBPath)
		}
	}

	agg := state.New(ck, rpc, cfg.PollInterval, log)
	agg.Store = blockStore
	agg.MempoolBaseURL = cfg.MempoolBaseURL

	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()

	api := httpapi.New(agg, log)

	// Wire snapshot refreshes into the WebSocket hub so subscribers get
	// real-time updates without polling.
	agg.OnRefresh = api.Hub.Broadcast

	// Optional: bitcoind hashblock ZMQ subscription for sub-second
	// chain-tip refreshes. Empty endpoint disables it.
	zmq := zmqmon.New(cfg.BitcoinZMQBlock, log)
	go zmq.Run(ctx)

	go agg.Run(ctx, zmq.Events)

	// Background reconciliation: retry hash/reward enrichment for blocks
	// the initial RPC lookup couldn't fetch, and detect chain reorgs by
	// comparing recorded hashes against the canonical chain.
	go agg.ReconcileBlocks(ctx)

	// Tail the ckpool log for block-solve events (our own solves).
	tailer := logmon.New(cfg.CKPoolLogFile, log)
	if blockStore != nil {
		const cursorKey = "logmon_cursor"
		tailer.LoadCursor = func() (uint64, int64, bool) {
			v, err := blockStore.GetKV(cursorKey)
			if err != nil || v == "" {
				return 0, 0, false
			}
			parts := strings.SplitN(v, ":", 2)
			if len(parts) != 2 {
				return 0, 0, false
			}
			ino, err1 := strconv.ParseUint(parts[0], 10, 64)
			off, err2 := strconv.ParseInt(parts[1], 10, 64)
			if err1 != nil || err2 != nil {
				return 0, 0, false
			}
			return ino, off, true
		}
		tailer.SaveCursor = func(ino uint64, off int64) {
			if err := blockStore.SetKV(cursorKey, fmt.Sprintf("%d:%d", ino, off)); err != nil {
				log.Warn("logmon cursor persist failed", "err", err)
			}
		}
	}
	go tailer.Run(ctx)
	go agg.IngestBlockEvents(ctx, tailer.Events)
	go agg.IngestAttemptEvents(ctx, tailer.Attempts)

	// Fallback block submitter: if ckpool's primary bitcoind doesn't
	// accept a block, the patched local_block_submit leaves the raw
	// hex sitting in PENDING_BLOCKS_DIR. This watcher re-broadcasts it
	// via the operator-configured BACKUP_RPC_URLS list.
	if cfg.PendingBlocksDir != "" {
		fallbacks := parseBackupRPCs(cfg.BackupRPCURLs, log)
		sub := &blocksubmit.Submitter{
			Dir:       cfg.PendingBlocksDir,
			Grace:     cfg.PendingBlocksGrace,
			Primary:   rpc,
			Fallbacks: fallbacks,
			Log:       log,
			OnSuccess: func(height int64, viaURL, viaLabel string) {
				agg.RecordFallbackSubmit(height, viaLabel)
			},
		}
		// Sweep every second so we react within ~grace+1s of a
		// failed submit. Reading an empty directory is cheap.
		go sub.Run(ctx, 1*time.Second)
	} else {
		log.Info("blocksubmit fallback disabled (PENDING_BLOCKS_DIR not set)")
	}

	// Wait briefly for the aggregator's first refresh to complete so
	// the very first /api/snapshot or /api/health hit doesn't see an
	// all-zeros snapshot and report bitcoin_ok=false during its own
	// initialization. Cap the wait so a permanently-down bitcoind
	// can't block startup forever — /healthz is honest about the
	// degraded state.
	select {
	case <-agg.Ready():
		log.Info("first snapshot ready")
	case <-time.After(8 * time.Second):
		log.Warn("first snapshot not ready within 8s, serving HTTP anyway (snapshot will be partial until backends respond)")
	case <-ctx.Done():
		return
	}

	srv := &http.Server{
		Addr:              cfg.ListenAddr,
		Handler:           api.Handler(),
		ReadHeaderTimeout: 5 * time.Second,
	}

	// Shutdown on ctx cancel
	go func() {
		<-ctx.Done()
		log.Info("shutting down")
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		_ = srv.Shutdown(shutdownCtx)
	}()

	log.Info("http listening", "addr", cfg.ListenAddr)
	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Error("http server", "err", err)
		os.Exit(1)
	}
}

// parseBackupRPCs splits BACKUP_RPC_URLS (newline- or comma-separated)
// into FallbackTargets. Credentials are accepted inline as
// https://user:pass@host:port/. Lines beginning with '#' are comments.
// Whitespace and empty lines are ignored.
func parseBackupRPCs(raw string, log *slog.Logger) []blocksubmit.FallbackTarget {
	if raw == "" {
		return nil
	}
	separated := strings.NewReplacer(",", "\n").Replace(raw)
	var out []blocksubmit.FallbackTarget
	for _, line := range strings.Split(separated, "\n") {
		line = strings.TrimSpace(line)
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		u, err := url.Parse(line)
		if err != nil {
			log.Warn("blocksubmit: invalid fallback URL, skipping", "raw", line, "err", err)
			continue
		}
		var user, pass string
		if u.User != nil {
			user = u.User.Username()
			pass, _ = u.User.Password()
			u.User = nil
		}
		clean := u.String()
		out = append(out, blocksubmit.FallbackTarget{
			URL:      clean,
			User:     user,
			Password: pass,
			Label:    u.Host,
		})
		log.Info("blocksubmit fallback registered", "url", clean, "host", u.Host, "auth", user != "")
	}
	return out
}