package sql

import (
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"strconv"
	"strings"

	"go.skia.org/infra/go/jsonutils"
	"go.skia.org/infra/go/skerr"
	"go.skia.org/infra/golden/go/sql/schema"
	"go.skia.org/infra/golden/go/types"
)

// DigestToBytes returns the given digest as bytes. It returns an error if a missing digest is
// passed in or if the bytes are otherwise invalid.
func DigestToBytes(d types.Digest) (schema.DigestBytes, error) {
	if len(d) != 32 {
		return schema.DigestBytes{}, skerr.Fmt("Empty/missing/invalid digest passed in %q", d)
	}
	out := make(schema.DigestBytes, md5.Size)
	_, err := hex.Decode(out, []byte(d))
	return out, skerr.Wrap(err)
}

// SerializeMap returns the given map in JSON and the MD5 of that json string. nil maps will be
// treated as empty maps. Keys will be sorted lexicographically.
func SerializeMap(m map[string]string) (string, []byte) {
	var jsonBytes []byte
	if len(m) == 0 {
		jsonBytes = []byte("{}")
	} else {
		jsonBytes = jsonutils.MarshalStringMap(m)
	}

	h := md5.Sum(jsonBytes)
	return string(jsonBytes), h[:]
}

// TraceValuesShards is the number of shards we use in the TraceValues Table.
const TraceValuesShards = 8

// ComputeTraceValueShard computes a shard in the range [0,TraceValuesShards) based off the given
// trace hash bytes. This shard range was chosen to be a small number (relative to the thousands
// of ranges that the TraceValues database occupies) that is larger than the number of nodes in the
// cockroachdb cluster. See the overall design doc (go/skia-gold-sql) for more explanation about
// data locality and sharding.
func ComputeTraceValueShard(traceID schema.TraceID) byte {
	return traceID[0] % TraceValuesShards
}

// AsMD5Hash returns the given byte slice as an MD5Hash (for easier use with maps)
func AsMD5Hash(b []byte) schema.MD5Hash {
	var m schema.MD5Hash
	copy(m[:], b)
	return m
}

// FromMD5Hash returns the given byte array a slice of bytes. The copy is required when dealing
// with a loop variable, as a naive slice won't work.
func FromMD5Hash(m schema.MD5Hash) []byte {
	b := make([]byte, len(m))
	copy(b, m[:])
	return b
}

// ValuesPlaceholders returns a set of SQL placeholder numbers grouped for use in an INSERT
// statement. For example, ValuesPlaceholders(2,3) returns ($1, $2), ($3, $4), ($5, $6)
// It panics if either param is <= 0.
func ValuesPlaceholders(valuesPerRow, numRows int) string {
	if valuesPerRow <= 0 || numRows <= 0 {
		panic("Cannot make ValuesPlaceholder with 0 rows or 0 values per row")
	}
	values := strings.Builder{}
	// There are at most 5 bytes per value that need to be written
	values.Grow(5 * valuesPerRow * numRows)
	// All WriteString calls below return nil errors, as specified in the documentation of
	// strings.Builder, so it is safe to ignore them.
	for argIdx := 1; argIdx <= valuesPerRow*numRows; argIdx += valuesPerRow {
		if argIdx != 1 {
			_, _ = values.WriteString(",")
		}
		_, _ = values.WriteString("(")
		for i := 0; i < valuesPerRow; i++ {
			if i != 0 {
				_, _ = values.WriteString(",")
			}
			_, _ = values.WriteString("$")
			_, _ = values.WriteString(strconv.Itoa(argIdx + i))
		}
		_, _ = values.WriteString(")")
	}
	return values.String()
}

// GetConnectionURL returns a full connection URL with the correct protocol and connection options
// given the username, host, port, and database name.
func GetConnectionURL(userHostPort, dbName string) string {
	// We choose not to use SSL because all communication should be in the same k8s cluster
	// and the cumbersomeness of using https is not yet worth it.
	return fmt.Sprintf("postgresql://%s/%s?sslmode=disable", userHostPort, dbName)
}

// Qualify prefixes the given CL, PS or TJ id with the given system. In the SQL database, we use
// these qualified IDs to make the queries easier, that is, we don't have to do a join over id
// and system, we can just use the combined ID.
func Qualify(system, id string) string {
	return system + "_" + id
}

// Unqualify removes the system prefix that was added with Qualify. If the id was not qualified,
// the input string is returned unchanged.
func Unqualify(id string) string {
	pieces := strings.SplitAfterN(id, "_", 2)
	if len(pieces) != 2 {
		return id
	}
	return pieces[1]
}

// Sanitize removes unsafe characters from strings to avoid SQL injections. Namely quotes.
func Sanitize(s string) string {
	s = strings.ReplaceAll(s, `'`, ``)
	return strings.ReplaceAll(s, `"`, ``)
}