const http = require('http')
const net = require('net')
const crypto = require('crypto')
const {
  checkPassword,
  createSession,
  isValidSession,
} = require('./auth')
const {
  listAddresses,
  addAddress,
  removeAddress,
} = require('./addresses')

const port = 8080
const fulcrumTimeoutMs = 3000

function queryFulcrum(fulcrumUrl, method, params = []) {
  return new Promise((resolve) => {
    if (!fulcrumUrl) {
      resolve({
        ok: false,
        result: null,
        error: 'Fulcrum URL is not configured',
      })
      return
    }

    let parsed

    try {
      parsed = new URL(fulcrumUrl)
    } catch {
      resolve({
        ok: false,
        result: null,
        error: 'Invalid Fulcrum URL',
      })
      return
    }

    if (parsed.protocol !== 'tcp:') {
      resolve({
        ok: false,
        result: null,
        error: 'Fulcrum URL must use tcp://',
      })
      return
    }

    const host = parsed.hostname
    const fulcrumPort = Number(parsed.port)

    if (!host || !fulcrumPort) {
      resolve({
        ok: false,
        result: null,
        error: 'Fulcrum URL is missing host or port',
      })
      return
    }

    const socket = net.createConnection({
      host,
      port: fulcrumPort,
    })

    let response = ''
    let settled = false

    const finish = (value) => {
      if (settled) return

      settled = true
      socket.destroy()
      resolve(value)
    }

    socket.setTimeout(fulcrumTimeoutMs)

    socket.on('connect', () => {
      console.log(
        `Fulcrum connected for ${method} (${host}:${fulcrumPort})`,
      )

      const request =
        JSON.stringify({
          jsonrpc: '2.0',
          id: 1,
          method,
          params,
        }) + '\n'

      console.log(`Sending Fulcrum request: ${request.trim()}`)

      socket.write(request)
    })

    socket.on('data', (data) => {
      const chunk = data.toString()

      console.log(`Fulcrum response data: ${chunk.trim()}`)

      response += chunk

      const lines = response.split('\n')

      for (const line of lines) {
        if (!line.trim()) continue

        let message

        try {
          message = JSON.parse(line)
        } catch {
          continue
        }

        if (message.error) {
          console.error(
            `Fulcrum returned an error for ${method}:`,
            JSON.stringify(message.error),
          )

          finish({
            ok: false,
            result: null,
            error: message.error,
          })

          return
        }

        if (
          Object.prototype.hasOwnProperty.call(
            message,
            'result',
          )
        ) {
          finish({
            ok: true,
            result: message.result,
            error: null,
          })

          return
        }
      }
    })

    socket.on('timeout', () => {
      console.error(
        `Fulcrum request timed out after ${fulcrumTimeoutMs}ms: ${method}`,
      )

      finish({
        ok: false,
        result: null,
        error: 'Connection timed out',
      })
    })

    socket.on('error', (error) => {
      console.error(
        `Fulcrum socket error for ${method}:`,
        error.message,
      )

      finish({
        ok: false,
        result: null,
        error: error.message,
      })
    })

    socket.on('close', (hadError) => {
      console.log(
        `Fulcrum socket closed for ${method}; hadError=${hadError}`,
      )

      if (!settled) {
        finish({
          ok: false,
          result: null,
          error: 'Connection closed before a response was received',
        })
      }
    })
  })
}

const BECH32_CHARSET =
  'qpzry9x8gf2tvdw0s3jn54khce6mua7l'

function bech32Polymod(values) {
  const generators = [
    0x3b6a57b2,
    0x26508e6d,
    0x1ea119fa,
    0x3d4233dd,
    0x2a1462b3,
  ]

  let chk = 1

  for (const value of values) {
    const top = chk >>> 25
    chk = ((chk & 0x1ffffff) << 5) ^ value

    for (let i = 0; i < 5; i++) {
      if ((top >>> i) & 1) {
        chk ^= generators[i]
      }
    }
  }

  return chk >>> 0
}

function bech32HrpExpand(hrp) {
  const values = []

  for (const char of hrp) {
    values.push(char.charCodeAt(0) >> 5)
  }

  values.push(0)

  for (const char of hrp) {
    values.push(char.charCodeAt(0) & 31)
  }

  return values
}

function bech32VerifyChecksum(hrp, data) {
  const polymod = bech32Polymod([
    ...bech32HrpExpand(hrp),
    ...data,
  ])

  return polymod === 1 || polymod === 0x2bc830a3
}

function bech32Decode(address) {
  if (typeof address !== 'string') {
    throw new Error('Bitcoin address must be a string')
  }

  if (address.length < 8 || address.length > 90) {
    throw new Error('Invalid Bitcoin address length')
  }

  const hasLower = address !== address.toUpperCase()
  const hasUpper = address !== address.toLowerCase()

  if (hasLower && hasUpper) {
    throw new Error('Bitcoin address must not mix uppercase and lowercase')
  }

  const normalized = address.toLowerCase()
  const separator = normalized.lastIndexOf('1')

  if (separator < 1 || separator + 7 > normalized.length) {
    throw new Error('Invalid Bech32 separator')
  }

  const hrp = normalized.slice(0, separator)
  const dataPart = normalized.slice(separator + 1)

  const data = []

  for (const char of dataPart) {
    const value = BECH32_CHARSET.indexOf(char)

    if (value === -1) {
      throw new Error('Invalid Bech32 character')
    }

    data.push(value)
  }

  if (!bech32VerifyChecksum(hrp, data)) {
    throw new Error('Invalid Bitcoin address checksum')
  }

  return {
    hrp,
    data: data.slice(0, -6),
    spec:
      bech32Polymod([
        ...bech32HrpExpand(hrp),
        ...data,
      ]) === 1
        ? 'bech32'
        : 'bech32m',
  }
}

function convertBits(data, fromBits, toBits, pad) {
  let accumulator = 0
  let bits = 0
  const result = []
  const maxValue = (1 << toBits) - 1

  for (const value of data) {
    if (value < 0 || value >> fromBits !== 0) {
      throw new Error('Invalid bit conversion input')
    }

    accumulator =
      (accumulator << fromBits) | value
    bits += fromBits

    while (bits >= toBits) {
      bits -= toBits
      result.push(
        (accumulator >> bits) & maxValue,
      )
    }
  }

  if (pad) {
    if (bits > 0) {
      result.push(
        (accumulator << (toBits - bits)) & maxValue,
      )
    }
  } else {
    if (bits >= fromBits) {
      throw new Error('Invalid padding')
    }

    if (
      ((accumulator << (toBits - bits)) &
        maxValue) !==
      0
    ) {
      throw new Error('Non-zero padding')
    }
  }

  return result
}

function addressToScriptPubKey(address) {
  const decoded = bech32Decode(address)

  if (decoded.hrp !== 'bc') {
    throw new Error(
      'Only mainnet Bitcoin addresses are supported',
    )
  }

  if (decoded.data.length < 1) {
    throw new Error('Invalid SegWit address')
  }

  const witnessVersion = decoded.data[0]

  if (witnessVersion > 16) {
    throw new Error('Invalid SegWit witness version')
  }

  if (
    witnessVersion === 0 &&
    decoded.spec !== 'bech32'
  ) {
    throw new Error(
      'Witness version 0 must use Bech32',
    )
  }

  if (
    witnessVersion !== 0 &&
    decoded.spec !== 'bech32m'
  ) {
    throw new Error(
      'Witness version 1+ must use Bech32m',
    )
  }

  const program = convertBits(
    decoded.data.slice(1),
    5,
    8,
    false,
  )

  if (program.length < 2 || program.length > 40) {
    throw new Error('Invalid witness program length')
  }

  if (
    witnessVersion === 0 &&
    program.length !== 20 &&
    program.length !== 32
  ) {
    throw new Error(
      'Invalid witness version 0 program length',
    )
  }

  const versionOpcode =
    witnessVersion === 0
      ? 0x00
      : 0x50 + witnessVersion

  const script = Buffer.from([
    versionOpcode,
    program.length,
    ...program,
  ])

  return script
}

function scriptPubKeyToScripthash(scriptPubKey) {
  const hash = crypto
    .createHash('sha256')
    .update(scriptPubKey)
    .digest()

  return Buffer.from(hash)
    .reverse()
    .toString('hex')
}

function addressToScripthash(address) {
  const scriptPubKey =
    addressToScriptPubKey(address)

  return scriptPubKeyToScripthash(scriptPubKey)
}

async function getAddressData(
  fulcrumUrl,
  address,
) {
  let scripthash

  try {
    scripthash = addressToScripthash(address)
  } catch (error) {
    return {
      address,
      balance: null,
      utxos: [],
      history: [],
      error:
        error instanceof Error
          ? error.message
          : 'Invalid Bitcoin address',
    }
  }

  const balance = await queryFulcrum(
    fulcrumUrl,
    'blockchain.scripthash.get_balance',
    [scripthash],
  )

  const utxos = await queryFulcrum(
    fulcrumUrl,
    'blockchain.scripthash.listunspent',
    [scripthash],
  )

  const history = await queryFulcrum(
    fulcrumUrl,
    'blockchain.scripthash.get_history',
    [scripthash],
  )

  return {
    address,
    scripthash,
    balance: balance.ok
      ? balance.result
      : null,
    utxos: utxos.ok
      ? utxos.result
      : [],
    history: history.ok
      ? history.result
      : [],
    error:
      balance.ok &&
      utxos.ok &&
      history.ok
        ? null
        : {
            balance: balance.ok
              ? null
              : balance.error,
            utxos: utxos.ok
              ? null
              : utxos.error,
            history: history.ok
              ? null
              : history.error,
          },
  }
}

async function getFulcrumStatus(
  fulcrumUrl,
) {
  const version = await queryFulcrum(
    fulcrumUrl,
    'server.version',
    ['Munin Bitcoin', '1.4'],
  )

  if (!version.ok) {
    return {
      configured: Boolean(fulcrumUrl),
      connected: false,
      url: fulcrumUrl,
      serverVersion: null,
      blockchainHeight: null,
      error: version.error,
    }
  }

  const headers = await queryFulcrum(
    fulcrumUrl,
    'blockchain.headers.subscribe',
    [],
  )

  return {
    configured: Boolean(fulcrumUrl),
    connected: true,
    url: fulcrumUrl,
    serverVersion: version.result,
    blockchainHeight:
      headers.ok && headers.result
        ? headers.result.height ?? null
        : null,
    error: headers.ok ? null : headers.error,
  }
}

async function getStatus() {
  const fulcrumUrl =
    process.env.MUNIN_FULCRUM_URL || null

  const fulcrum =
    await getFulcrumStatus(fulcrumUrl)

  return {
    service: 'running',
    fulcrum,
    wallet: 'not configured',
    labels: 0,
    transactions: 0,
    lastScan: 'never',
  }
}

function sendJson(
  res,
  statusCode,
  body,
) {
  res.writeHead(statusCode, {
    'Content-Type': 'application/json',
  })

  res.end(JSON.stringify(body))
}

function readRequestBody(req) {
  return new Promise((resolve, reject) => {
    let body = ''

    req.on('data', (chunk) => {
      body += chunk
    })

    req.on('end', () => {
      resolve(body)
    })

    req.on('error', reject)
  })
}

const server = http.createServer(
  async (req, res) => {
    if (
      req.method === 'POST' &&
      req.url === '/api/login'
    ) {
      try {
        const body =
          await readRequestBody(req)

        const input = JSON.parse(body)

        if (!checkPassword(input.password)) {
          sendJson(res, 401, {
            error: 'Invalid password',
          })
          return
        }

        const token = createSession()

        res.writeHead(200, {
          'Content-Type': 'application/json',
          'Set-Cookie':
            'munin_session=' +
            encodeURIComponent(token) +
            '; HttpOnly; Secure; SameSite=Strict; Path=/; Max-Age=86400',
        })

        res.end(
          JSON.stringify({
            ok: true,
          }),
        )
      } catch {
        sendJson(res, 400, {
          error: 'Invalid request',
        })
      }

      return
    }

    if (
      req.method === 'GET' &&
      req.url === '/api/addresses'
    ) {
      if (!isValidSession(req)) {
        sendJson(res, 401, {
          error: 'Authentication required',
        })
        return
      }

      try {
        const addresses =
          await listAddresses()

        sendJson(res, 200, {
          addresses,
        })
      } catch (error) {
        console.error(
          'Failed to list addresses:',
          error,
        )

        sendJson(res, 500, {
          error:
            'Failed to read address watchlist',
        })
      }

      return
    }

    if (
      req.method === 'GET' &&
      req.url === '/api/addresses/data'
    ) {
      if (!isValidSession(req)) {
        sendJson(res, 401, {
          error: 'Authentication required',
        })
        return
      }

      try {
        const fulcrumUrl =
          process.env.MUNIN_FULCRUM_URL ||
          null

        if (!fulcrumUrl) {
          sendJson(res, 503, {
            error:
              'Fulcrum URL is not configured',
          })
          return
        }

        const addresses =
          await listAddresses()

        const results = []

        for (const entry of addresses) {
          results.push(
            await getAddressData(
              fulcrumUrl,
              entry.address,
            ),
          )
        }

        sendJson(res, 200, {
          addresses: results,
        })
      } catch (error) {
        console.error(
          'Failed to get address data:',
          error,
        )

        sendJson(res, 500, {
          error:
            'Failed to retrieve address data',
        })
      }

      return
    }

    if (
      req.method === 'POST' &&
      req.url === '/api/addresses'
    ) {
      if (!isValidSession(req)) {
        sendJson(res, 401, {
          error: 'Authentication required',
        })
        return
      }

      try {
        const body =
          await readRequestBody(req)

        const input = JSON.parse(body)

        const entry = await addAddress(
          input.address,
          input.label,
        )

        sendJson(res, 201, entry)
      } catch (error) {
        const message =
          error instanceof Error
            ? error.message
            : 'Failed to add address'

        sendJson(res, 400, {
          error: message,
        })
      }

      return
    }

    if (
      req.method === 'DELETE' &&
      req.url === '/api/addresses'
    ) {
      if (!isValidSession(req)) {
        sendJson(res, 401, {
          error: 'Authentication required',
        })
        return
      }

      try {
        const body =
          await readRequestBody(req)

        const input = JSON.parse(body)

        await removeAddress(input.address)

        sendJson(res, 200, {
          ok: true,
        })
      } catch (error) {
        const message =
          error instanceof Error
            ? error.message
            : 'Failed to remove address'

        sendJson(res, 400, {
          error: message,
        })
      }

      return
    }

    if (req.url === '/api/status') {
      if (!isValidSession(req)) {
        sendJson(res, 401, {
          error: 'Authentication required',
        })
        return
      }

      try {
        const status = await getStatus()

        sendJson(res, 200, status)
      } catch (error) {
        console.error(
          'Failed to get service status:',
          error,
        )

        sendJson(res, 500, {
          service: 'running',
          error:
            'Failed to determine service status',
        })
      }

      return
    }

    res.writeHead(404)
    res.end('Not found')
  },
)

server.listen(port, () => {
  console.log(
    `Status API listening on port ${port}`,
  )
})