// storaged is the object I/O service. D2 wires GET / PUT / LIST /
// DELETE routes against a single bucket ("primary") in the registry.
// Bind is 127.0.0.1 only (G0 dev — no auth on the wire); body cap is
// 256 MiB; concurrent in-flight PUTs are capped at 4 with non-blocking
// try-acquire (503 + Retry-After when full).
package main

import (
	"context"
	"encoding/json"
	"errors"
	"flag"
	"io"
	"log/slog"
	"net/http"
	"os"
	"strings"

	"github.com/go-chi/chi/v5"

	"git.agentview.dev/profit/golangLAKEHOUSE/internal/secrets"
	"git.agentview.dev/profit/golangLAKEHOUSE/internal/shared"
	"git.agentview.dev/profit/golangLAKEHOUSE/internal/storaged"
)

const (
	maxPutBytes      = 256 << 20 // 256 MiB per Qwen Q1 fix
	maxConcurrentPut = 4         // 4-slot semaphore on in-flight PUTs
	retryAfterSecs   = "5"       // Retry-After header on 503
	primaryBucket    = "primary"
)

func main() {
	configPath := flag.String("config", "lakehouse.toml", "path to TOML config")
	secretsPath := flag.String("secrets", "/etc/lakehouse/secrets-go.toml", "path to secrets TOML (Go-side; Rust uses /etc/lakehouse/secrets.toml)")
	flag.Parse()

	cfg, err := shared.LoadConfig(*configPath)
	if err != nil {
		slog.Error("config", "err", err)
		os.Exit(1)
	}

	registry, err := buildRegistry(cfg, *secretsPath)
	if err != nil {
		slog.Error("bucket registry", "err", err)
		os.Exit(1)
	}

	h := newHandlers(registry)

	if err := shared.Run("storaged", cfg.Storaged.Bind, h.register); err != nil {
		slog.Error("server", "err", err)
		os.Exit(1)
	}
}

// buildRegistry constructs the (single, G0) bucket registry. Multi-bucket
// federation lands in G2; the registry shape is in place so that arrives
// without an HTTP-layer refactor.
func buildRegistry(cfg shared.Config, secretsPath string) (*storaged.BucketRegistry, error) {
	prov, err := secrets.NewFileProvider(secretsPath, secrets.S3Credentials{
		AccessKeyID:     cfg.S3.AccessKeyID,
		SecretAccessKey: cfg.S3.SecretAccessKey,
	})
	if err != nil {
		return nil, err
	}

	// Per Opus C1 review: don't tie the AWS config-load context to a
	// canceller that fires when buildRegistry returns. With static creds
	// it's fine today, but EC2 IMDS / SSO / AssumeRole credential
	// providers (G2+) capture the load ctx for refresh — a cancelled
	// ctx silently fails them at the next refresh. Use Background here;
	// per-request lifetimes flow through r.Context() in handlers.
	bucket, err := storaged.NewBucket(context.Background(), cfg.S3, prov, primaryBucket)
	if err != nil {
		return nil, err
	}

	reg := storaged.NewRegistry()
	if err := reg.Register(bucket); err != nil {
		return nil, err
	}
	return reg, nil
}

// handlers carries the registry + the PUT semaphore. One instance
// per process; chi routes close over it.
type handlers struct {
	reg    *storaged.BucketRegistry
	putSem chan struct{}
}

func newHandlers(reg *storaged.BucketRegistry) *handlers {
	return &handlers{
		reg:    reg,
		putSem: make(chan struct{}, maxConcurrentPut),
	}
}

func (h *handlers) register(r chi.Router) {
	// Verb-paths per PHASE_G0_KICKOFF D2.4 spec. REST-style refactor
	// (GET/PUT/DELETE on a single /storage/{key}) deferred until G2.
	r.Get("/storage/get/*", h.handleGet)
	r.Put("/storage/put/*", h.handlePut)
	r.Get("/storage/list", h.handleList)
	r.Delete("/storage/delete/*", h.handleDelete)
}

// extractKey pulls the wildcard key out of a chi route. Routes are
// registered as `/storage/<verb>/*` so the wildcard captures the
// remainder, including embedded slashes.
func extractKey(r *http.Request) string {
	// chi.URLParam with "*" returns everything after the route prefix.
	return chi.URLParam(r, "*")
}

// validateKey rejects keys that would be unsafe to round-trip through
// the system. The exact policy is a G0 design choice — see the focused
// decision request in the D2 PR description (validateKey-policy).
func validateKey(key string) error {
	if key == "" {
		return errors.New("empty key")
	}
	if len(key) > 1024 {
		return errors.New("key too long (>1024 bytes)")
	}
	if strings.ContainsRune(key, 0) {
		return errors.New("key contains NUL byte")
	}
	if strings.HasPrefix(key, "/") {
		return errors.New("key starts with /")
	}
	for _, part := range strings.Split(key, "/") {
		if part == ".." {
			return errors.New("key contains .. component")
		}
	}
	if strings.ContainsAny(key, "\r\n\t") {
		return errors.New("key contains control char")
	}
	return nil
}

func (h *handlers) handleGet(w http.ResponseWriter, r *http.Request) {
	key := extractKey(r)
	if err := validateKey(key); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	bucket, err := h.reg.Resolve(primaryBucket)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	body, info, err := bucket.Get(r.Context(), key)
	if errors.Is(err, storaged.ErrKeyNotFound) {
		http.Error(w, "not found", http.StatusNotFound)
		return
	}
	if err != nil {
		slog.Error("storage get", "key", key, "err", err)
		http.Error(w, "internal", http.StatusInternalServerError)
		return
	}
	defer body.Close()
	if info.ETag != "" {
		w.Header().Set("ETag", info.ETag)
	}
	w.Header().Set("Content-Type", "application/octet-stream")
	if _, err := io.Copy(w, body); err != nil {
		slog.Warn("storage get copy", "key", key, "err", err)
	}
}

func (h *handlers) handlePut(w http.ResponseWriter, r *http.Request) {
	key := extractKey(r)
	if err := validateKey(key); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	// Up-front Content-Length cap. Per Opus C3 review: the
	// manager.Uploader's multipart path runs body reads in goroutines
	// and wraps errors in its own types, so *http.MaxBytesError can be
	// buried by the time it reaches us — meaning bodies just over the
	// 5 MiB multipart threshold could surface as 500 instead of 413.
	// Catching Content-Length up front returns 413 deterministically
	// when the client honestly declares size; MaxBytesReader + the
	// string-match fallback below cover chunked / lying-CL cases.
	if r.ContentLength > maxPutBytes {
		w.Header().Set("Retry-After", retryAfterSecs)
		http.Error(w, "payload too large", http.StatusRequestEntityTooLarge)
		return
	}

	// Non-blocking try-acquire: if the 4-slot semaphore is full, return
	// 503 + Retry-After:5 instantly rather than holding the connection.
	// Per PHASE_G0_KICKOFF D2.4: "PUTs blocked on the semaphore → 503
	// with Retry-After: 5".
	select {
	case h.putSem <- struct{}{}:
		defer func() { <-h.putSem }()
	default:
		w.Header().Set("Retry-After", retryAfterSecs)
		http.Error(w, "storaged: put concurrency cap reached", http.StatusServiceUnavailable)
		return
	}

	// 256 MiB per-request body cap. Reads beyond this surface as
	// *http.MaxBytesError; for chunked-encoding bodies that's the only
	// signal we get. Defer LIFO order: r.Body.Close fires before
	// <-h.putSem, so the body is fully drained before the slot frees.
	r.Body = http.MaxBytesReader(w, r.Body, maxPutBytes)
	defer r.Body.Close()

	bucket, err := h.reg.Resolve(primaryBucket)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if err := bucket.Put(r.Context(), key, r.Body); err != nil {
		// Two-layer detect: errors.As catches the typed error when it
		// survives unwrapping; the string-suffix check catches cases
		// where manager.Uploader's multipart path wraps the body-read
		// failure in its own aggregate type.
		var maxErr *http.MaxBytesError
		if errors.As(err, &maxErr) || strings.Contains(err.Error(), "http: request body too large") {
			w.Header().Set("Retry-After", retryAfterSecs)
			http.Error(w, "payload too large", http.StatusRequestEntityTooLarge)
			return
		}
		slog.Error("storage put", "key", key, "err", err)
		http.Error(w, "internal", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write([]byte(`{"status":"ok"}`))
}

func (h *handlers) handleList(w http.ResponseWriter, r *http.Request) {
	prefix := r.URL.Query().Get("prefix")
	bucket, err := h.reg.Resolve(primaryBucket)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	objs, err := bucket.List(r.Context(), prefix)
	if err != nil {
		slog.Error("storage list", "prefix", prefix, "err", err)
		http.Error(w, "internal", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{
		"prefix":  prefix,
		"objects": objs,
	})
}

func (h *handlers) handleDelete(w http.ResponseWriter, r *http.Request) {
	key := extractKey(r)
	if err := validateKey(key); err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}
	bucket, err := h.reg.Resolve(primaryBucket)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if err := bucket.Delete(r.Context(), key); err != nil {
		slog.Error("storage delete", "key", key, "err", err)
		http.Error(w, "internal", http.StatusInternalServerError)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}