package parse

import (
	"fmt"
	"net"
	"net/url"
	"strings"

	"github.com/elastic/beats/metricbeat/mb"

	"github.com/pkg/errors"
)

// URLHostParserBuilder builds a tailored HostParser for used with host strings
// that are URLs.
type URLHostParserBuilder struct {
	PathConfigKey string
	DefaultPath   string
	DefaultScheme string
	QueryParams   string
}

// Build returns a new HostParser function whose behavior is influenced by the
// options set in URLHostParserBuilder.
func (b URLHostParserBuilder) Build() mb.HostParser {
	return func(module mb.Module, host string) (mb.HostData, error) {
		conf := map[string]interface{}{}
		err := module.UnpackConfig(conf)
		if err != nil {
			return mb.HostData{}, err
		}

		var user, pass, path string
		t, ok := conf["username"]
		if ok {
			user, ok = t.(string)
			if !ok {
				return mb.HostData{}, errors.Errorf("'username' config for module %v is not a string", module.Name())
			}
		}
		t, ok = conf["password"]
		if ok {
			pass, ok = t.(string)
			if !ok {
				return mb.HostData{}, errors.Errorf("'password' config for module %v is not a string", module.Name())
			}
		}
		t, ok = conf[b.PathConfigKey]
		if ok {
			path, ok = t.(string)
			if !ok {
				return mb.HostData{}, errors.Errorf("'%v' config for module %v is not a string", b.PathConfigKey, module.Name())
			}
		} else {
			path = b.DefaultPath
		}

		return ParseURL(host, b.DefaultScheme, user, pass, path, b.QueryParams)
	}
}

// NewHostDataFromURL returns a new HostData based on the contents of the URL.
// If the URLs scheme is "unix" or end is "unix" (e.g. "http+unix://") then
// the HostData.Host field is set to the URLs path instead of the URLs host,
// the same happens for "npipe".
func NewHostDataFromURL(u *url.URL) mb.HostData {
	var user, pass string
	if u.User != nil {
		user = u.User.Username()
		pass, _ = u.User.Password()
	}

	host := u.Host
	if strings.HasSuffix(u.Scheme, "unix") || strings.HasSuffix(u.Scheme, "npipe") {
		host = u.Path
	}

	return mb.HostData{
		URI:          u.String(),
		SanitizedURI: redactURLCredentials(u).String(),
		Host:         host,
		User:         user,
		Password:     pass,
	}
}

// ParseURL returns HostData object from a raw 'host' value and a series of
// defaults that are added to the URL if not present in the rawHost value.
// Values from the rawHost take precedence over the defaults.
func ParseURL(rawHost, scheme, user, pass, path, query string) (mb.HostData, error) {
	u, err := getURL(rawHost, scheme, user, pass, path, query)
	if err != nil {
		return mb.HostData{}, err
	}

	return NewHostDataFromURL(u), nil
}

// SetURLUser set the user credentials in the given URL. If the username or
// password is not set in the URL then the default is used (if provided).
func SetURLUser(u *url.URL, defaultUser, defaultPass string) {
	var user, pass string
	var userIsSet, passIsSet bool
	if u.User != nil {
		user = u.User.Username()
		if user != "" {
			userIsSet = true
		}
		pass, passIsSet = u.User.Password()
	}

	if !userIsSet && defaultUser != "" {
		userIsSet = true
		user = defaultUser
	}

	if !passIsSet && defaultPass != "" {
		passIsSet = true
		pass = defaultPass
	}

	if userIsSet && passIsSet {
		u.User = url.UserPassword(user, pass)
	} else if userIsSet {
		u.User = url.User(user)
	}
}

// getURL constructs a URL from the rawHost value and adds the provided user,
// password, path, and query params if one was not set in the rawURL value.
func getURL(rawURL, scheme, username, password, path, query string) (*url.URL, error) {
	if parts := strings.SplitN(rawURL, "://", 2); len(parts) != 2 {
		// Add scheme.
		rawURL = fmt.Sprintf("%s://%s", scheme, rawURL)
	}

	u, err := url.Parse(rawURL)
	if err != nil {
		return nil, fmt.Errorf("error parsing URL: %v", err)
	}

	SetURLUser(u, username, password)

	if !strings.HasSuffix(u.Scheme, "unix") && !strings.HasSuffix(u.Scheme, "npipe") {
		if u.Host == "" {
			return nil, fmt.Errorf("error parsing URL: empty host")
		}

		// Validate the host. The port is optional.
		host, _, err := net.SplitHostPort(u.Host)
		if err != nil {
			if strings.Contains(err.Error(), "missing port") {
				host = u.Host
			} else {
				return nil, fmt.Errorf("error parsing URL: %v", err)
			}
		}
		if host == "" {
			return nil, fmt.Errorf("error parsing URL: empty host")
		}
	}

	if u.Path == "" && path != "" {
		// The path given in the host config takes precedence over the
		// default path.
		if !strings.HasPrefix(path, "/") {
			path = "/" + path
		}
		u.Path = path
	}

	// Add the query params to existing query parameters overwriting any
	// keys that already exist.
	q := u.Query()
	params, err := url.ParseQuery(query)
	for key, values := range params {
		for _, v := range values {
			q.Set(key, v)
		}
	}
	u.RawQuery = q.Encode()

	return u, nil
}

// redactURLCredentials returns the URL as a string with the username and
// password redacted.
func redactURLCredentials(u *url.URL) *url.URL {
	redacted := *u
	redacted.User = nil
	return &redacted
}