// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"math"
	"net/http"
	"os"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/shirou/gopsutil/v3/mem"

	"github.com/minio/minio/internal/config/api"
	xioutil "github.com/minio/minio/internal/ioutil"
	"github.com/minio/minio/internal/logger"
	"github.com/minio/minio/internal/mcontext"
)

type apiConfig struct {
	mu sync.RWMutex

	requestsDeadline time.Duration
	requestsPool     chan struct{}
	clusterDeadline  time.Duration
	listQuorum       string
	corsAllowOrigins []string
	// total drives per erasure set across pools.
	totalDriveCount       int
	replicationPriority   string
	replicationMaxWorkers int
	transitionWorkers     int

	staleUploadsExpiry          time.Duration
	staleUploadsCleanupInterval time.Duration
	deleteCleanupInterval       time.Duration
	enableODirect               bool
	gzipObjects                 bool
	rootAccess                  bool
	syncEvents                  bool
	objectMaxVersions           int64
}

const (
	cgroupV1MemLimitFile = "/sys/fs/cgroup/memory/memory.limit_in_bytes"
	cgroupV2MemLimitFile = "/sys/fs/cgroup/memory.max"
	cgroupMemNoLimit     = 9223372036854771712
)

func cgroupMemLimit() (limit uint64) {
	buf, err := os.ReadFile(cgroupV2MemLimitFile)
	if err != nil {
		buf, err = os.ReadFile(cgroupV1MemLimitFile)
	}
	if err != nil {
		return 0
	}
	limit, err = strconv.ParseUint(strings.TrimSpace(string(buf)), 10, 64)
	if err != nil {
		// The kernel can return valid but non integer values
		// but still, no need to interpret more
		return 0
	}
	if limit == cgroupMemNoLimit {
		// No limit set, It's the highest positive signed 64-bit
		// integer (2^63-1), rounded down to multiples of 4096 (2^12),
		// the most common page size on x86 systems - for cgroup_limits.
		return 0
	}
	return limit
}

func availableMemory() (available uint64) {
	available = 2048 * blockSizeV2 * 2 // Default to 4 GiB when we can't find the limits.

	if runtime.GOOS == "linux" {
		// Useful in container mode
		limit := cgroupMemLimit()
		if limit > 0 {
			// A valid value is found, return its 75%
			available = (limit * 3) / 4
			return
		}
	} // for all other platforms limits are based on virtual memory.

	memStats, err := mem.VirtualMemory()
	if err != nil {
		return
	}
	// A valid value is available return its 75%
	available = (memStats.Available * 3) / 4
	return
}

func (t *apiConfig) init(cfg api.Config, setDriveCounts []int) {
	t.mu.Lock()
	defer t.mu.Unlock()

	clusterDeadline := cfg.ClusterDeadline
	if clusterDeadline == 0 {
		clusterDeadline = 10 * time.Second
	}
	t.clusterDeadline = clusterDeadline
	corsAllowOrigin := cfg.CorsAllowOrigin
	if len(corsAllowOrigin) == 0 {
		corsAllowOrigin = []string{"*"}
	}
	t.corsAllowOrigins = corsAllowOrigin

	maxSetDrives := 0
	for _, setDriveCount := range setDriveCounts {
		t.totalDriveCount += setDriveCount
		if setDriveCount > maxSetDrives {
			maxSetDrives = setDriveCount
		}
	}

	var apiRequestsMaxPerNode int
	if cfg.RequestsMax <= 0 {
		// Returns 75% of max memory allowed
		maxMem := availableMemory()

		// max requests per node is calculated as
		// total_ram / ram_per_request
		// ram_per_request is (2MiB+128KiB) * driveCount \
		//    + 2 * 10MiB (default erasure block size v1) + 2 * 1MiB (default erasure block size v2)
		blockSize := xioutil.BlockSizeLarge + xioutil.BlockSizeSmall
		apiRequestsMaxPerNode = int(maxMem / uint64(maxSetDrives*blockSize+int(blockSizeV1*2+blockSizeV2*2)))
		if globalIsDistErasure {
			logger.Info("Automatically configured API requests per node based on available memory on the system: %d", apiRequestsMaxPerNode)
		}
	} else {
		apiRequestsMaxPerNode = cfg.RequestsMax
		if n := totalNodeCount(); n > 0 {
			apiRequestsMaxPerNode /= n
		}
	}

	if cap(t.requestsPool) != apiRequestsMaxPerNode {
		// Only replace if needed.
		// Existing requests will use the previous limit,
		// but new requests will use the new limit.
		// There will be a short overlap window,
		// but this shouldn't last long.
		t.requestsPool = make(chan struct{}, apiRequestsMaxPerNode)
	}
	t.requestsDeadline = cfg.RequestsDeadline
	listQuorum := cfg.ListQuorum
	if listQuorum == "" {
		listQuorum = "strict"
	}
	t.listQuorum = listQuorum
	if globalReplicationPool != nil &&
		(cfg.ReplicationPriority != t.replicationPriority || cfg.ReplicationMaxWorkers != t.replicationMaxWorkers) {
		globalReplicationPool.ResizeWorkerPriority(cfg.ReplicationPriority, cfg.ReplicationMaxWorkers)
	}
	t.replicationPriority = cfg.ReplicationPriority
	t.replicationMaxWorkers = cfg.ReplicationMaxWorkers

	// N B api.transition_workers will be deprecated
	if globalTransitionState != nil {
		globalTransitionState.UpdateWorkers(cfg.TransitionWorkers)
	}
	t.transitionWorkers = cfg.TransitionWorkers

	t.staleUploadsExpiry = cfg.StaleUploadsExpiry
	t.staleUploadsCleanupInterval = cfg.StaleUploadsCleanupInterval
	t.deleteCleanupInterval = cfg.DeleteCleanupInterval
	t.enableODirect = cfg.EnableODirect
	t.gzipObjects = cfg.GzipObjects
	t.rootAccess = cfg.RootAccess
	t.syncEvents = cfg.SyncEvents
	t.objectMaxVersions = cfg.ObjectMaxVersions
}

func (t *apiConfig) odirectEnabled() bool {
	t.mu.RLock()
	defer t.mu.RUnlock()

	return t.enableODirect
}

func (t *apiConfig) shouldGzipObjects() bool {
	t.mu.RLock()
	defer t.mu.RUnlock()

	return t.gzipObjects
}

func (t *apiConfig) permitRootAccess() bool {
	t.mu.RLock()
	defer t.mu.RUnlock()

	return t.rootAccess
}

func (t *apiConfig) getListQuorum() string {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.listQuorum == "" {
		return "strict"
	}

	return t.listQuorum
}

func (t *apiConfig) getCorsAllowOrigins() []string {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if len(t.corsAllowOrigins) == 0 {
		return []string{"*"}
	}

	corsAllowOrigins := make([]string, len(t.corsAllowOrigins))
	copy(corsAllowOrigins, t.corsAllowOrigins)
	return corsAllowOrigins
}

func (t *apiConfig) getStaleUploadsCleanupInterval() time.Duration {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.staleUploadsCleanupInterval == 0 {
		return 6 * time.Hour // default 6 hours
	}

	return t.staleUploadsCleanupInterval
}

func (t *apiConfig) getStaleUploadsExpiry() time.Duration {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.staleUploadsExpiry == 0 {
		return 24 * time.Hour // default 24 hours
	}

	return t.staleUploadsExpiry
}

func (t *apiConfig) getDeleteCleanupInterval() time.Duration {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.deleteCleanupInterval == 0 {
		return 5 * time.Minute // every 5 minutes
	}

	return t.deleteCleanupInterval
}

func (t *apiConfig) getClusterDeadline() time.Duration {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.clusterDeadline == 0 {
		return 10 * time.Second
	}

	return t.clusterDeadline
}

func (t *apiConfig) getRequestsPoolCapacity() int {
	t.mu.RLock()
	defer t.mu.RUnlock()

	return cap(t.requestsPool)
}

func (t *apiConfig) getRequestsPool() (chan struct{}, time.Duration) {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.requestsPool == nil {
		return nil, 10 * time.Second
	}

	if t.requestsDeadline <= 0 {
		return t.requestsPool, 10 * time.Second
	}

	return t.requestsPool, t.requestsDeadline
}

// maxClients throttles the S3 API calls
func maxClients(f http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		globalHTTPStats.incS3RequestsIncoming()

		if r.Header.Get(globalObjectPerfUserMetadata) == "" {
			if val := globalServiceFreeze.Load(); val != nil {
				if unlock, ok := val.(chan struct{}); ok && unlock != nil {
					// Wait until unfrozen.
					select {
					case <-unlock:
					case <-r.Context().Done():
						// if client canceled we don't need to wait here forever.
						return
					}
				}
			}
		}

		pool, deadline := globalAPIConfig.getRequestsPool()
		if pool == nil {
			f.ServeHTTP(w, r)
			return
		}

		globalHTTPStats.addRequestsInQueue(1)

		if tc, ok := r.Context().Value(mcontext.ContextTraceKey).(*mcontext.TraceCtxt); ok {
			tc.FuncName = "s3.MaxClients"
		}

		deadlineTimer := time.NewTimer(deadline)
		defer deadlineTimer.Stop()

		select {
		case pool <- struct{}{}:
			defer func() { <-pool }()
			globalHTTPStats.addRequestsInQueue(-1)
			f.ServeHTTP(w, r)
		case <-deadlineTimer.C:
			// Send a http timeout message
			writeErrorResponse(r.Context(), w,
				errorCodes.ToAPIErr(ErrTooManyRequests),
				r.URL)
			globalHTTPStats.addRequestsInQueue(-1)
			return
		case <-r.Context().Done():
			// When the client disconnects before getting the S3 handler
			// status code response, set the status code to 499 so this request
			// will be properly audited and traced.
			w.WriteHeader(499)
			globalHTTPStats.addRequestsInQueue(-1)
			return
		}
	}
}

func (t *apiConfig) getReplicationOpts() replicationPoolOpts {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.replicationPriority == "" {
		return replicationPoolOpts{
			Priority:   "auto",
			MaxWorkers: WorkerMaxLimit,
		}
	}

	return replicationPoolOpts{
		Priority:   t.replicationPriority,
		MaxWorkers: t.replicationMaxWorkers,
	}
}

func (t *apiConfig) getTransitionWorkers() int {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.transitionWorkers <= 0 {
		return runtime.GOMAXPROCS(0) / 2
	}

	return t.transitionWorkers
}

func (t *apiConfig) isSyncEventsEnabled() bool {
	t.mu.RLock()
	defer t.mu.RUnlock()

	return t.syncEvents
}

func (t *apiConfig) getObjectMaxVersions() int64 {
	t.mu.RLock()
	defer t.mu.RUnlock()

	if t.objectMaxVersions <= 0 {
		// defaults to 'IntMax' when unset.
		return math.MaxInt64
	}

	return t.objectMaxVersions
}