// Package spamc provides a client for the SpamAssassin spamd protocol.
// http://svn.apache.org/repos/asf/spamassassin/trunk/spamd/PROTOCOL
//
// Modified to add timeouts from https://github.com/cgt/spamc
package spamc

import (
	"bufio"
	"fmt"
	"io"
	"net"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/axllent/mailpit/internal/tools"
)

// ProtoVersion is the protocol version
const ProtoVersion = "1.5"

var (
	spamInfoRe    = regexp.MustCompile(`(.+)\/(.+) (\d+) (.+)`)
	spamMainRe    = regexp.MustCompile(`^Spam: (.+) ; (.+) . (.+)$`)
	spamDetailsRe = regexp.MustCompile(`^\s?(-?[0-9\.]+)\s([a-zA-Z0-9_]*)(\W*)(.*)`)
)

// connection is like net.Conn except that it also has a CloseWrite method.
// CloseWrite is implemented by net.TCPConn and net.UnixConn, but for some
// reason it is not present in the net.Conn interface.
type connection interface {
	net.Conn
	CloseWrite() error
}

// Client is a spamd client.
type Client struct {
	net     string
	addr    string
	timeout int
}

// NewTCP returns a *Client that connects to spamd via the given TCP address.
func NewTCP(addr string, timeout int) *Client {
	return &Client{"tcp", addr, timeout}
}

// NewUnix returns a *Client that connects to spamd via the given Unix socket.
func NewUnix(addr string) *Client {
	return &Client{"unix", addr, 0}
}

// Rule represents a matched SpamAssassin rule.
type Rule struct {
	Points      string
	Name        string
	Description string
}

// Result struct
type Result struct {
	ResponseCode int
	Message      string
	Spam         bool
	Score        float64
	Threshold    float64
	Rules        []Rule
}

// dial connects to spamd through TCP or a Unix socket.
func (c *Client) dial() (connection, error) {
	if c.net == "tcp" {
		tcpAddr, err := net.ResolveTCPAddr("tcp", c.addr)
		if err != nil {
			return nil, err
		}
		return net.DialTCP("tcp", nil, tcpAddr)
	} else if c.net == "unix" {
		unixAddr, err := net.ResolveUnixAddr("unix", c.addr)
		if err != nil {
			return nil, err
		}
		return net.DialUnix("unix", nil, unixAddr)
	}

	panic("Client.net must be either \"tcp\" or \"unix\"")
}

// Report checks if message is spam or not, and returns score plus report
func (c *Client) Report(email []byte) (Result, error) {
	output, err := c.report(email)
	if err != nil {
		return Result{}, err
	}

	return c.parseOutput(output), nil
}

func (c *Client) report(email []byte) ([]string, error) {
	conn, err := c.dial()
	if err != nil {
		return nil, err
	}

	defer conn.Close()

	if err := conn.SetDeadline(time.Now().Add(time.Duration(c.timeout) * time.Second)); err != nil {
		return nil, err
	}

	bw := bufio.NewWriter(conn)
	if _, err := bw.WriteString("REPORT SPAMC/" + ProtoVersion + "\r\n"); err != nil {
		return nil, err
	}

	if _, err := bw.WriteString("Content-length: " + strconv.Itoa(len(email)) + "\r\n\r\n"); err != nil {
		return nil, err
	}

	if _, err := bw.Write(email); err != nil {
		return nil, err
	}

	if err := bw.Flush(); err != nil {
		return nil, err
	}

	// Client is supposed to close its writing side of the connection
	// after sending its request.
	if err := conn.CloseWrite(); err != nil {
		return nil, err
	}

	var (
		lines []string
		br    = bufio.NewReader(conn)
	)

	for {
		line, err := br.ReadString('\n')
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, err
		}
		line = strings.TrimRight(line, " \t\r\n")
		lines = append(lines, line)
	}

	// join lines, and replace multi-line descriptions with single line for each
	tmp := strings.Join(lines, "\n")
	re := regexp.MustCompile("\n                            ")
	n := re.ReplaceAllString(tmp, " ")

	//split lines again
	return strings.Split(n, "\n"), nil
}

func (c *Client) parseOutput(output []string) Result {
	var result Result
	var reachedRules bool
	for _, row := range output {
		// header
		if spamInfoRe.MatchString(row) {
			res := spamInfoRe.FindStringSubmatch(row)
			if len(res) == 5 {
				resCode, err := strconv.Atoi(res[3])
				if err == nil {
					result.ResponseCode = resCode
				}
				result.Message = res[4]
				continue
			}
		}

		// summary
		if spamMainRe.MatchString(row) {
			res := spamMainRe.FindStringSubmatch(row)
			if len(res) == 4 {
				if tools.InArray(res[1], []string{"true", "yes"}) {
					result.Spam = true
				} else {
					result.Spam = false
				}
				resFloat, err := strconv.ParseFloat(res[2], 32)
				if err == nil {
					result.Score = resFloat
					continue
				}
				resFloat, err = strconv.ParseFloat(res[3], 32)
				if err == nil {
					result.Threshold = resFloat
					continue
				}
			}
		}

		if strings.HasPrefix(row, "Content analysis details") {
			reachedRules = true
			continue
		}

		// details
		if reachedRules && spamDetailsRe.MatchString(row) {
			res := spamDetailsRe.FindStringSubmatch(row)
			if len(res) == 5 {
				rule := Rule{Points: res[1], Name: res[2], Description: res[4]}
				result.Rules = append(result.Rules, rule)
			}
		}
	}

	return result
}

// Ping the spamd
func (c *Client) Ping() error {
	conn, err := c.dial()
	if err != nil {
		return err
	}
	defer conn.Close()

	if err := conn.SetDeadline(time.Now().Add(time.Duration(c.timeout) * time.Second)); err != nil {
		return err
	}

	if _, err := io.WriteString(conn, fmt.Sprintf("PING SPAMC/%s\r\n\r\n", ProtoVersion)); err != nil {
		return err
	}

	if err := conn.CloseWrite(); err != nil {
		return err
	}

	br := bufio.NewReader(conn)
	for {
		_, err = br.ReadSlice('\n')
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
	}

	return nil
}