when (NimMajor, NimMinor) < (1, 4):
  {.push raises: [Defect].}
else:
  {.push raises: [].}

import
  std/[options, sequtils],
  stew/[results, byteutils],
  sqlite3_abi
import
  ../../../common/databases/db_sqlite,
  ../../../common/databases/common,
  ../../../waku_core,
  ./cursor

const DbTable = "Message"

type SqlQueryStr = string

### SQLite column helper methods

proc queryRowWakuMessageCallback(s: ptr sqlite3_stmt, contentTopicCol, payloadCol, versionCol, senderTimestampCol: cint): WakuMessage =
  let
    topic = cast[ptr UncheckedArray[byte]](sqlite3_column_blob(s, contentTopicCol))
    topicLength = sqlite3_column_bytes(s, contentTopicCol)
    contentTopic = string.fromBytes(@(toOpenArray(topic, 0, topicLength-1)))
  let
    p = cast[ptr UncheckedArray[byte]](sqlite3_column_blob(s, payloadCol))
    length = sqlite3_column_bytes(s, payloadCol)
    payload = @(toOpenArray(p, 0, length-1))
  let version = sqlite3_column_int64(s, versionCol)
  let senderTimestamp = sqlite3_column_int64(s, senderTimestampCol)

  WakuMessage(
    contentTopic: ContentTopic(contentTopic),
    payload: payload ,
    version: uint32(version),
    timestamp: Timestamp(senderTimestamp)
  )

proc queryRowReceiverTimestampCallback(s: ptr sqlite3_stmt, storedAtCol: cint): Timestamp =
  let storedAt = sqlite3_column_int64(s, storedAtCol)
  Timestamp(storedAt)

proc queryRowPubsubTopicCallback(s: ptr sqlite3_stmt, pubsubTopicCol: cint): PubsubTopic =
  let
    pubsubTopicPointer = cast[ptr UncheckedArray[byte]](sqlite3_column_blob(s, pubsubTopicCol))
    pubsubTopicLength = sqlite3_column_bytes(s, pubsubTopicCol)
    pubsubTopic = string.fromBytes(@(toOpenArray(pubsubTopicPointer, 0, pubsubTopicLength-1)))

  pubsubTopic

proc queryRowDigestCallback(s: ptr sqlite3_stmt, digestCol: cint): seq[byte] =
  let
    digestPointer = cast[ptr UncheckedArray[byte]](sqlite3_column_blob(s, digestCol))
    digestLength = sqlite3_column_bytes(s, digestCol)
    digest = @(toOpenArray(digestPointer, 0, digestLength-1))

  digest


### SQLite queries

## Create table

proc createTableQuery(table: string): SqlQueryStr =
  "CREATE TABLE IF NOT EXISTS " & table & " (" &
  " pubsubTopic BLOB NOT NULL," &
  " contentTopic BLOB NOT NULL," &
  " payload BLOB," &
  " version INTEGER NOT NULL," &
  " timestamp INTEGER NOT NULL," &
  " id BLOB," &
  " storedAt INTEGER NOT NULL," &
  " CONSTRAINT messageIndex PRIMARY KEY (storedAt, id, pubsubTopic)" &
  ") WITHOUT ROWID;"

proc createTable*(db: SqliteDatabase): DatabaseResult[void] =
  let query = createTableQuery(DbTable)
  discard ?db.query(query, proc(s: ptr sqlite3_stmt) = discard)
  ok()

## Create indices

proc createOldestMessageTimestampIndexQuery(table: string): SqlQueryStr =
  "CREATE INDEX IF NOT EXISTS i_ts ON " & table & " (storedAt);"

proc createOldestMessageTimestampIndex*(db: SqliteDatabase):
                                        DatabaseResult[void] =
  let query = createOldestMessageTimestampIndexQuery(DbTable)
  discard ?db.query(query, proc(s: ptr sqlite3_stmt) = discard)
  ok()


proc createHistoryQueryIndexQuery(table: string): SqlQueryStr =
  "CREATE INDEX IF NOT EXISTS i_query ON " & table & " (contentTopic, pubsubTopic, storedAt, id);"

proc createHistoryQueryIndex*(db: SqliteDatabase): DatabaseResult[void] =
  let query = createHistoryQueryIndexQuery(DbTable)
  discard ?db.query(query, proc(s: ptr sqlite3_stmt) = discard)
  ok()


## Insert message
type InsertMessageParams* = (seq[byte], Timestamp, seq[byte], seq[byte], seq[byte], int64, Timestamp)

proc insertMessageQuery(table: string): SqlQueryStr =
  "INSERT INTO " & table & "(id, storedAt, contentTopic, payload, pubsubTopic, version, timestamp)" &
  " VALUES (?, ?, ?, ?, ?, ?, ?);"

proc prepareInsertMessageStmt*(db: SqliteDatabase): SqliteStmt[InsertMessageParams, void] =
  let query = insertMessageQuery(DbTable)
  db.prepareStmt(query, InsertMessageParams, void).expect("this is a valid statement")


## Count table messages

proc countMessagesQuery(table: string): SqlQueryStr =
  "SELECT COUNT(*) FROM " & table

proc getMessageCount*(db: SqliteDatabase): DatabaseResult[int64] =
  var count: int64
  proc queryRowCallback(s: ptr sqlite3_stmt) =
    count = sqlite3_column_int64(s, 0)

  let query = countMessagesQuery(DbTable)
  let res = db.query(query, queryRowCallback)
  if res.isErr():
    return err("failed to count number of messages in the database")

  ok(count)

## Get oldest message receiver timestamp

proc selectOldestMessageTimestampQuery(table: string): SqlQueryStr =
  "SELECT MIN(storedAt) FROM " & table

proc selectOldestReceiverTimestamp*(db: SqliteDatabase):
                                    DatabaseResult[Timestamp] {.inline.}=
  var timestamp: Timestamp
  proc queryRowCallback(s: ptr sqlite3_stmt) =
    timestamp = queryRowReceiverTimestampCallback(s, 0)

  let query = selectOldestMessageTimestampQuery(DbTable)
  let res = db.query(query, queryRowCallback)
  if res.isErr():
    return err("failed to get the oldest receiver timestamp from the database")

  ok(timestamp)

## Get newest message receiver timestamp

proc selectNewestMessageTimestampQuery(table: string): SqlQueryStr =
  "SELECT MAX(storedAt) FROM " & table

proc selectNewestReceiverTimestamp*(db: SqliteDatabase):
                                    DatabaseResult[Timestamp] {.inline.}=
  var timestamp: Timestamp
  proc queryRowCallback(s: ptr sqlite3_stmt) =
    timestamp = queryRowReceiverTimestampCallback(s, 0)

  let query = selectNewestMessageTimestampQuery(DbTable)
  let res = db.query(query, queryRowCallback)
  if res.isErr():
    return err("failed to get the newest receiver timestamp from the database")

  ok(timestamp)

## Delete messages older than timestamp

proc deleteMessagesOlderThanTimestampQuery(table: string, ts: Timestamp): SqlQueryStr =
  "DELETE FROM " & table & " WHERE storedAt < " & $ts

proc deleteMessagesOlderThanTimestamp*(db: SqliteDatabase, ts: int64):
                                       DatabaseResult[void] =
  let query = deleteMessagesOlderThanTimestampQuery(DbTable, ts)
  discard ?db.query(query, proc(s: ptr sqlite3_stmt) = discard)
  ok()


## Delete oldest messages not within limit

proc deleteOldestMessagesNotWithinLimitQuery(table: string, limit: int): SqlQueryStr =
  "DELETE FROM " & table & " WHERE (storedAt, id, pubsubTopic) NOT IN (" &
  " SELECT storedAt, id, pubsubTopic FROM " & table &
  " ORDER BY storedAt DESC, id DESC" &
  " LIMIT " & $limit &
  ");"

proc deleteOldestMessagesNotWithinLimit*(db: SqliteDatabase, limit: int):
                                         DatabaseResult[void] =
  # NOTE: The word `limit` here refers the store capacity/maximum number-of-messages allowed limit
  let query = deleteOldestMessagesNotWithinLimitQuery(DbTable, limit=limit)
  discard ?db.query(query, proc(s: ptr sqlite3_stmt) = discard)
  ok()

## Select all messages

proc selectAllMessagesQuery(table: string): SqlQueryStr =
  "SELECT storedAt, contentTopic, payload, pubsubTopic, version, timestamp, id" &
  " FROM " & table &
  " ORDER BY storedAt ASC"

proc selectAllMessages*(db: SqliteDatabase): DatabaseResult[seq[(PubsubTopic,
                                                                 WakuMessage,
                                                                 seq[byte],
                                                                 Timestamp)]] =
  ## Retrieve all messages from the store.
  var rows: seq[(PubsubTopic, WakuMessage, seq[byte], Timestamp)]
  proc queryRowCallback(s: ptr sqlite3_stmt) =
    let
      pubsubTopic = queryRowPubsubTopicCallback(s, pubsubTopicCol=3)
      wakuMessage = queryRowWakuMessageCallback(s, contentTopicCol=1, payloadCol=2, versionCol=4, senderTimestampCol=5)
      digest = queryRowDigestCallback(s, digestCol=6)
      storedAt = queryRowReceiverTimestampCallback(s, storedAtCol=0)

    rows.add((pubsubTopic, wakuMessage, digest, storedAt))

  let query = selectAllMessagesQuery(DbTable)
  let res = db.query(query, queryRowCallback)
  if res.isErr():
    return err(res.error())

  ok(rows)

## Select messages by history query with limit

proc combineClauses(clauses: varargs[Option[string]]): Option[string] =
  let whereSeq = @clauses.filterIt(it.isSome()).mapIt(it.get())
  if whereSeq.len <= 0:
    return none(string)

  var where: string = whereSeq[0]
  for clause in whereSeq[1..^1]:
    where &= " AND " & clause
  some(where)

proc whereClause(cursor: Option[DbCursor],
                 pubsubTopic: Option[PubsubTopic],
                 contentTopic: seq[ContentTopic],
                 startTime: Option[Timestamp],
                 endTime: Option[Timestamp],
                 ascending: bool): Option[string] =

  let cursorClause = if cursor.isNone():
        none(string)
      else:
        let comp = if ascending: ">" else: "<"
        some("(storedAt, id) " & comp & " (?, ?)")

  let pubsubTopicClause = if pubsubTopic.isNone():
        none(string)
      else:
        some("pubsubTopic = (?)")

  let contentTopicClause = if contentTopic.len <= 0:
        none(string)
      else:
        var where = "contentTopic IN ("
        where &= "?"
        for _ in 1..<contentTopic.len:
          where &= ", ?"
        where &= ")"
        some(where)

  let startTimeClause = if startTime.isNone():
        none(string)
      else:
        some("storedAt >= (?)")

  let endTimeClause = if endTime.isNone():
        none(string)
      else:
        some("storedAt <= (?)")

  combineClauses(cursorClause, pubsubTopicClause, contentTopicClause, startTimeClause, endTimeClause)

proc selectMessagesWithLimitQuery(table: string, where: Option[string], limit: uint, ascending=true): SqlQueryStr =
  let order = if ascending: "ASC" else: "DESC"

  var query: string

  query = "SELECT storedAt, contentTopic, payload, pubsubTopic, version, timestamp, id"
  query &= " FROM " & table

  if where.isSome():
    query &= " WHERE " & where.get()

  query &= " ORDER BY storedAt " & order & ", id " & order
  query &= " LIMIT " & $limit & ";"

  query

proc prepareSelectMessagesWithlimitStmt(db: SqliteDatabase, stmt: string): DatabaseResult[SqliteStmt[void, void]] =
  var s: RawStmtPtr
  checkErr sqlite3_prepare_v2(db.env, stmt, stmt.len.cint, addr s, nil)
  ok(SqliteStmt[void, void](s))

proc execSelectMessagesWithLimitStmt(s: SqliteStmt,
                          cursor: Option[DbCursor],
                          pubsubTopic: Option[PubsubTopic],
                          contentTopic: seq[ContentTopic],
                          startTime: Option[Timestamp],
                          endTime: Option[Timestamp],
                          onRowCallback: DataProc): DatabaseResult[void] =
  let s = RawStmtPtr(s)

  # Bind params
  var paramIndex = 1

  if cursor.isSome():  # cursor = storedAt, id, pubsubTopic
    let (storedAt, id, _) = cursor.get()
    checkErr bindParam(s, paramIndex, storedAt)
    paramIndex += 1
    checkErr bindParam(s, paramIndex, id)
    paramIndex += 1

  if pubsubTopic.isSome():
    let pubsubTopic = toBytes(pubsubTopic.get())
    checkErr bindParam(s, paramIndex, pubsubTopic)
    paramIndex += 1

  for topic in contentTopic:
    checkErr bindParam(s, paramIndex, topic.toBytes())
    paramIndex += 1

  if startTime.isSome():
    let time = startTime.get()
    checkErr bindParam(s, paramIndex, time)
    paramIndex += 1

  if endTime.isSome():
    let time = endTime.get()
    checkErr bindParam(s, paramIndex, time)
    paramIndex += 1


  try:
    while true:
      let v = sqlite3_step(s)
      case v
      of SQLITE_ROW:
        onRowCallback(s)
      of SQLITE_DONE:
        return ok()
      else:
        return err($sqlite3_errstr(v))
  finally:
    # release implicit transaction
    discard sqlite3_reset(s) # same return information as step
    discard sqlite3_clear_bindings(s) # no errors possible

proc selectMessagesByHistoryQueryWithLimit*(db: SqliteDatabase,
                                            contentTopic: seq[ContentTopic],
                                            pubsubTopic: Option[PubsubTopic],
                                            cursor: Option[DbCursor],
                                            startTime: Option[Timestamp],
                                            endTime: Option[Timestamp],
                                            limit: uint,
                                            ascending: bool):
                                            DatabaseResult[seq[(PubsubTopic,
                                                                WakuMessage,
                                                                seq[byte],
                                                                Timestamp)]] =


  var messages: seq[(PubsubTopic, WakuMessage, seq[byte], Timestamp)] = @[]
  proc queryRowCallback(s: ptr sqlite3_stmt) =
    let
      pubsubTopic = queryRowPubsubTopicCallback(s, pubsubTopicCol=3)
      message = queryRowWakuMessageCallback(s, contentTopicCol=1, payloadCol=2, versionCol=4, senderTimestampCol=5)
      digest = queryRowDigestCallback(s, digestCol=6)
      storedAt = queryRowReceiverTimestampCallback(s, storedAtCol=0)

    messages.add((pubsubTopic, message, digest, storedAt))

  let query = block:
    let where = whereClause(cursor, pubsubTopic, contentTopic, startTime, endTime, ascending)
    selectMessagesWithLimitQuery(DbTable, where, limit, ascending)

  let dbStmt = ?db.prepareSelectMessagesWithlimitStmt(query)
  ?dbStmt.execSelectMessagesWithLimitStmt(
    cursor,
    pubsubTopic,
    contentTopic,
    startTime,
    endTime,
    queryRowCallback
  )
  dbStmt.dispose()

  ok(messages)