package tsdb

import (
	"errors"
	"fmt"
	"log"
	"os"
	"time"

	"github.com/influxdb/influxdb/toml"
)

const (
	// DefaultEngine is the default engine for new shards
	DefaultEngine = "bz1"

	// DefaultMaxWALSize is the default size of the WAL before it is flushed.
	DefaultMaxWALSize = 100 * 1024 * 1024 // 100MB

	// DefaultWALFlushInterval is the frequency the WAL will get flushed if
	// it doesn't reach its size threshold.
	DefaultWALFlushInterval = 10 * time.Minute

	// DefaultWALPartitionFlushDelay is the sleep time between WAL partition flushes.
	DefaultWALPartitionFlushDelay = 2 * time.Second

	// tsdb/engine/wal configuration options

	// DefaultReadySeriesSize of 32KB specifies when a series is eligible to be flushed
	DefaultReadySeriesSize = 30 * 1024

	// DefaultCompactionThreshold flush and compact a partition once this ratio of keys are over the flush size
	DefaultCompactionThreshold = 0.5

	// DefaultMaxSeriesSize specifies the size at which a series will be forced to flush
	DefaultMaxSeriesSize = 1024 * 1024

	// DefaultFlushColdInterval specifies how long after a partition has been cold
	// for writes that a full flush and compaction are forced
	DefaultFlushColdInterval = 5 * time.Second

	// DefaultParititionSizeThreshold specifies when a partition gets to this size in
	// memory, we should slow down writes until it gets a chance to compact.
	// This will force clients to get backpressure if they're writing too fast. We need
	// this because the WAL can take writes much faster than the index. So eventually
	// we'll need to create backpressure, otherwise we'll fill up the memory and die.
	// This number multiplied by the parition count is roughly the max possible memory
	// size for the in-memory WAL cache.
	DefaultPartitionSizeThreshold = 50 * 1024 * 1024 // 50MB

	// Default settings for TSM

	// DefaultCacheMaxMemorySize is the maximum size a shard's cache can
	// reach before it starts rejecting writes.
	DefaultCacheMaxMemorySize = 500 * 1024 * 1024 // 500MB

	// DefaultCacheSnapshotMemorySize is the size at which the engine will
	// snapshot the cache and write it to a TSM file, freeing up memory
	DefaultCacheSnapshotMemorySize = 25 * 1024 * 1024 // 25MB

	// DefaultCacheSnapshotWriteColdDuration is the length of time at which
	// the engine will snapshot the cache and write it to a new TSM file if
	// the shard hasn't receieved writes or deletes
	DefaultCacheSnapshotWriteColdDuration = time.Duration(time.Hour)

	// DefaultMinCompactionFileCount is the minimum number of TSM files
	// that need to exist before a compaction cycle will run
	DefaultCompactMinFileCount = 3

	// DefaultCompactFullWriteColdDuration is the duration at which the engine
	// will compact all TSM files in a shard if it hasn't received a write or delete
	DefaultCompactFullWriteColdDuration = time.Duration(24 * time.Hour)

	// DefaultMaxPointsPerBlock is the maximum number of points in an encoded
	// block in a TSM file
	DefaultMaxPointsPerBlock = 1000
)

type Config struct {
	Dir    string `toml:"dir"`
	Engine string `toml:"engine"`

	// WAL config options for b1 (introduced in 0.9.2)
	MaxWALSize             int           `toml:"max-wal-size"`
	WALFlushInterval       toml.Duration `toml:"wal-flush-interval"`
	WALPartitionFlushDelay toml.Duration `toml:"wal-partition-flush-delay"`

	// WAL configuration options for bz1 (introduced in 0.9.3)
	WALDir                    string        `toml:"wal-dir"`
	WALLoggingEnabled         bool          `toml:"wal-logging-enabled"`
	WALReadySeriesSize        int           `toml:"wal-ready-series-size"`
	WALCompactionThreshold    float64       `toml:"wal-compaction-threshold"`
	WALMaxSeriesSize          int           `toml:"wal-max-series-size"`
	WALFlushColdInterval      toml.Duration `toml:"wal-flush-cold-interval"`
	WALPartitionSizeThreshold uint64        `toml:"wal-partition-size-threshold"`

	// Query logging
	QueryLogEnabled bool `toml:"query-log-enabled"`

	// Compaction options for tsm1 (descriptions above with defaults)
	CacheMaxMemorySize             uint64        `toml:"cache-max-memory-size"`
	CacheSnapshotMemorySize        uint64        `toml:"cache-snapshot-memory-size"`
	CacheSnapshotWriteColdDuration toml.Duration `toml:"cache-snapshot-write-cold-duration"`
	CompactMinFileCount            int           `toml:"compact-min-file-count"`
	CompactFullWriteColdDuration   toml.Duration `toml:"compact-full-write-cold-duration"`
	MaxPointsPerBlock              int           `toml:"max-points-per-block"`
}

func NewConfig() Config {
	defaultEngine := DefaultEngine
	if engine := os.Getenv("INFLUXDB_DATA_ENGINE"); engine != "" {
		log.Println("TSDB engine selected via environment variable:", engine)
		defaultEngine = engine
	}

	return Config{
		Engine:                 defaultEngine,
		MaxWALSize:             DefaultMaxWALSize,
		WALFlushInterval:       toml.Duration(DefaultWALFlushInterval),
		WALPartitionFlushDelay: toml.Duration(DefaultWALPartitionFlushDelay),

		WALLoggingEnabled:         true,
		WALReadySeriesSize:        DefaultReadySeriesSize,
		WALCompactionThreshold:    DefaultCompactionThreshold,
		WALMaxSeriesSize:          DefaultMaxSeriesSize,
		WALFlushColdInterval:      toml.Duration(DefaultFlushColdInterval),
		WALPartitionSizeThreshold: DefaultPartitionSizeThreshold,

		QueryLogEnabled: true,

		CacheMaxMemorySize:             DefaultCacheMaxMemorySize,
		CacheSnapshotMemorySize:        DefaultCacheSnapshotMemorySize,
		CacheSnapshotWriteColdDuration: toml.Duration(DefaultCacheSnapshotWriteColdDuration),
		CompactMinFileCount:            DefaultCompactMinFileCount,
		CompactFullWriteColdDuration:   toml.Duration(DefaultCompactFullWriteColdDuration),
	}
}

func (c *Config) Validate() error {
	if c.Dir == "" {
		return errors.New("Data.Dir must be specified")
	} else if c.WALDir == "" {
		return errors.New("Data.WALDir must be specified")
	}

	valid := false
	for _, e := range RegisteredEngines() {
		if e == c.Engine {
			valid = true
			break
		}
	}
	if !valid {
		return fmt.Errorf("unrecognized engine %s", c.Engine)
	}

	return nil
}