package main

import (
	"log"
	"os"
	"os/signal"
	"syscall"
	"swoosh"
)

func main() {
	// Configuration from environment
	listenAddr := getEnv("SWOOSH_LISTEN_ADDR", ":8080")
	walDir := getEnv("SWOOSH_WAL_DIR", "./data/wal")
	snapshotPath := getEnv("SWOOSH_SNAPSHOT_PATH", "./data/snapshots/latest.json")

	log.Printf("SWOOSH starting...")
	log.Printf("  Listen: %s", listenAddr)
	log.Printf("  WAL: %s", walDir)
	log.Printf("  Snapshot: %s", snapshotPath)

	// Initialize production WAL store (BadgerDB)
	wal, err := swoosh.NewBadgerWALStore(walDir)
	if err != nil {
		log.Fatalf("failed to open WAL: %v", err)
	}
	defer wal.Close()

	// Initialize production snapshot store (atomic file writes)
	snapStore := swoosh.NewFileSnapshotStore(snapshotPath)

	// Recover state from snapshot + WAL replay
	state := recoverState(wal, snapStore)

	log.Printf("  Recovered state hash: %s", state.StateHash)
	log.Printf("  Licensed: %v", state.Boot.Licensed)
	log.Printf("  Quarantined: %v", state.Policy.Quarantined)
	log.Printf("  HLC last: %s", state.HLCLast)

	// Create initial snapshot if this is first boot
	snapshot := swoosh.Snapshot{
		State:            state,
		LastAppliedHLC:   state.HLCLast,
		LastAppliedIndex: wal.LastIndex(),
	}

	// Create nil guard provider for now
	// In production, implement GuardProvider with KACHING, BACKBEAT, HMMM, SHHH, MCP
	var guard swoosh.GuardProvider = nil

	// Initialize executor (single source of truth)
	executor := swoosh.NewExecutor(wal, snapStore, guard, snapshot)

	// Setup graceful shutdown
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)

	go func() {
		<-sigChan
		log.Println("Shutdown signal received, saving final snapshot...")

		// Get final state and save snapshot
		finalState := executor.GetStateSnapshot()
		finalSnapshot := swoosh.Snapshot{
			State:            finalState,
			LastAppliedHLC:   finalState.HLCLast,
			LastAppliedIndex: wal.LastIndex(),
		}

		if err := snapStore.Save(finalSnapshot); err != nil {
			log.Printf("WARNING: failed to save final snapshot: %v", err)
		} else {
			log.Printf("Final snapshot saved: hash=%s hlc=%s", finalState.StateHash, finalState.HLCLast)
		}

		if err := wal.Close(); err != nil {
			log.Printf("WARNING: failed to close WAL: %v", err)
		}

		os.Exit(0)
	}()

	// Start HTTP server (blocks until error or shutdown)
	log.Printf("HTTP server listening on %s", listenAddr)
	if err := swoosh.StartHTTPServer(listenAddr, executor); err != nil {
		log.Fatalf("HTTP server failed: %v", err)
	}
}

// recoverState loads the latest snapshot and replays WAL to reconstruct state.
//
// Recovery steps:
// 1. Attempt to load latest snapshot
// 2. If snapshot exists, use it as base state
// 3. If no snapshot, start from genesis state
// 4. Replay all WAL records since snapshot's LastAppliedIndex
// 5. Return fully recovered OrchestratorState
//
// This ensures crash recovery: even if crashed mid-transition, WAL replay
// deterministically reconstructs exact state.
func recoverState(wal *swoosh.BadgerWALStore, snapStore *swoosh.FileSnapshotStore) swoosh.OrchestratorState {
	var state swoosh.OrchestratorState
	var lastAppliedIndex uint64

	// Try to load latest snapshot
	snapshot, err := snapStore.LoadLatest()
	if err != nil {
		log.Printf("No snapshot found, starting from genesis: %v", err)
		state = genesisState()
		lastAppliedIndex = 0
	} else {
		log.Printf("Loaded snapshot: index=%d hlc=%s", snapshot.LastAppliedIndex, snapshot.LastAppliedHLC)
		state = snapshot.State
		lastAppliedIndex = snapshot.LastAppliedIndex
	}

	// Replay WAL records since snapshot
	records, err := wal.Replay(lastAppliedIndex + 1)
	if err != nil {
		log.Fatalf("WAL replay failed: %v", err)
	}

	if len(records) > 0 {
		log.Printf("Replaying %d WAL records from index %d...", len(records), lastAppliedIndex+1)

		// Replay each record deterministically
		// Use nil guard since guards were already evaluated during original execution
		nilGuard := swoosh.GuardOutcome{
			LicenseOK:  true,
			BackbeatOK: true,
			QuorumOK:   true,
			PolicyOK:   true,
			MCPHealthy: true,
		}

		for _, record := range records {
			// Apply transition using reducer (deterministic replay)
			newState, err := swoosh.Reduce(state, record.Transition, nilGuard)
			if err != nil {
				log.Printf("WARNING: replay error at index %d: %v", record.Index, err)
				// Continue replay - reducer may have evolved since record was written
				continue
			}

			// Verify state hash matches
			if newState.StateHash != record.StatePostHash {
				log.Printf("WARNING: state hash mismatch at index %d (expected=%s got=%s)",
					record.Index, record.StatePostHash, newState.StateHash)
			}

			state = newState
			lastAppliedIndex = record.Index
		}

		log.Printf("Replay complete: final index=%d hash=%s", lastAppliedIndex, state.StateHash)
	} else {
		log.Printf("No WAL records to replay")
	}

	return state
}

// genesisState returns the initial OrchestratorState for a fresh deployment.
func genesisState() swoosh.OrchestratorState {
	state := swoosh.OrchestratorState{
		Meta: struct {
			Version    string
			SchemaHash string
		}{
			Version:    "1.0.0",
			SchemaHash: "genesis",
		},
		HLCLast: "0-0-0000000000000000",
	}

	// Compute initial state hash
	hash, err := swoosh.ComputeStateHash(state)
	if err != nil {
		log.Printf("WARNING: failed to compute genesis state hash: %v", err)
		hash = "genesis-hash-unavailable"
	}
	state.StateHash = hash

	return state
}

func getEnv(key, fallback string) string {
	if value := os.Getenv(key); value != "" {
		return value
	}
	return fallback
}