coredns/core/setup/rewrite.go

package setup

import (
	"strconv"
	"strings"

	"github.com/miekg/coredns/middleware"
	"github.com/miekg/coredns/middleware/rewrite"
)

// Rewrite configures a new Rewrite middleware instance.
func Rewrite(c *Controller) (middleware.Middleware, error) {
	rewrites, err := rewriteParse(c)
	if err != nil {
		return nil, err
	}

	return func(next middleware.Handler) middleware.Handler {
		return rewrite.Rewrite{
			Next:  next,
			Rules: rewrites,
		}
	}, nil
}

func rewriteParse(c *Controller) ([]rewrite.Rule, error) {
	var simpleRules []rewrite.Rule
	var regexpRules []rewrite.Rule

	for c.Next() {
		var rule rewrite.Rule
		var err error
		var base = "."
		var pattern, to string
		var status int
		var ext []string

		args := c.RemainingArgs()

		var ifs []rewrite.If

		switch len(args) {
		case 1:
			base = args[0]
			fallthrough
		case 0:
			for c.NextBlock() {
				switch c.Val() {
				case "r", "regexp":
					if !c.NextArg() {
						return nil, c.ArgErr()
					}
					pattern = c.Val()
				case "to":
					args1 := c.RemainingArgs()
					if len(args1) == 0 {
						return nil, c.ArgErr()
					}
					to = strings.Join(args1, " ")
				case "ext": // TODO(miek): fix or remove
					args1 := c.RemainingArgs()
					if len(args1) == 0 {
						return nil, c.ArgErr()
					}
					ext = args1
				case "if":
					args1 := c.RemainingArgs()
					if len(args1) != 3 {
						return nil, c.ArgErr()
					}
					ifCond, err := rewrite.NewIf(args1[0], args1[1], args1[2])
					if err != nil {
						return nil, err
					}
					ifs = append(ifs, ifCond)
				case "status": // TODO(miek): fix or remove
					if !c.NextArg() {
						return nil, c.ArgErr()
					}
					status, _ = strconv.Atoi(c.Val())
					if status < 200 || (status > 299 && status < 400) || status > 499 {
						return nil, c.Err("status must be 2xx or 4xx")
					}
				default:
					return nil, c.ArgErr()
				}
			}
			// ensure to or status is specified
			if to == "" && status == 0 {
				return nil, c.ArgErr()
			}
			// TODO(miek): complex rules
			base, pattern, to, status, ext, ifs = base, pattern, to, status, ext, ifs
			err = err
			// if rule, err = rewrite.NewComplexRule(base, pattern, to, status, ext, ifs); err != nil {
			// return nil, err
			// }
			regexpRules = append(regexpRules, rule)

		// the only unhandled case is 2 and above
		default:
			rule = rewrite.NewSimpleRule(args[0], strings.Join(args[1:], " "))
			simpleRules = append(simpleRules, rule)
		}
	}

	// put simple rules in front to avoid regexp computation for them
	return append(simpleRules, regexpRules...), nil
}