feat: rewriter layer

internal/rule/engine.go

@@ -0,0 +1,45 @@
+package rule
+
+import (
+	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/vm"
+	"github.com/pkg/errors"
+)
+
+type Engine[E any] struct {
+	rules []*vm.Program
+}
+
+func (e *Engine[E]) Apply(env E) ([]any, error) {
+	results := make([]any, 0, len(e.rules))
+	for i, r := range e.rules {
+		result, err := expr.Run(r, env)
+		if err != nil {
+			return nil, errors.Wrapf(err, "could not run rule #%d", i)
+		}
+
+		results = append(results, result)
+	}
+
+	return results, nil
+}
+
+func NewEngine[E any](funcs ...OptionFunc) (*Engine[E], error) {
+	opts := NewOptions(funcs...)
+
+	engine := &Engine[E]{
+		rules: make([]*vm.Program, 0, len(opts.Rules)),
+	}
+
+	for i, r := range opts.Rules {
+
+		program, err := expr.Compile(r, opts.Expr...)
+		if err != nil {
+			return nil, errors.Wrapf(err, "could not compile rule #%d", i)
+		}
+
+		engine.rules = append(engine.rules, program)
+	}
+
+	return engine, nil
+}

internal/rule/http/option.go

@@ -0,0 +1,42 @@
+package http
+
+import (
+	"net/http"
+
+	"forge.cadoles.com/cadoles/bouncer/internal/rule"
+	"github.com/expr-lang/expr"
+)
+
+func WithRequestFuncs(r *http.Request) rule.OptionFunc {
+	return func(opts *rule.Options) {
+		funcs := []expr.Option{
+			setRequestURL(r),
+			setRequestHeaderFunc(r),
+			addRequestHeaderFunc(r),
+			delRequestHeadersFunc(r),
+			setRequestHostFunc(r),
+		}
+
+		if len(opts.Expr) == 0 {
+			opts.Expr = make([]expr.Option, 0)
+		}
+
+		opts.Expr = append(opts.Expr, funcs...)
+	}
+}
+
+func WithResponseFuncs(r *http.Response) rule.OptionFunc {
+	return func(opts *rule.Options) {
+		funcs := []expr.Option{
+			setResponseHeaderFunc(r),
+			addResponseHeaderFunc(r),
+			delResponseHeadersFunc(r),
+		}
+
+		if len(opts.Expr) == 0 {
+			opts.Expr = make([]expr.Option, 0)
+		}
+
+		opts.Expr = append(opts.Expr, funcs...)
+	}
+}

internal/rule/http/request.go

@@ -0,0 +1,122 @@
+package http
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"forge.cadoles.com/Cadoles/go-proxy/wildcard"
+	"github.com/expr-lang/expr"
+	"github.com/pkg/errors"
+)
+
+func setRequestHostFunc(r *http.Request) expr.Option {
+	return expr.Function(
+		"set_host",
+		func(params ...any) (any, error) {
+			host := params[0].(string)
+			r.Host = host
+
+			return true, nil
+		},
+		new(func(string) bool),
+	)
+}
+
+func setRequestURL(r *http.Request) expr.Option {
+	return expr.Function(
+		"set_url",
+		func(params ...any) (any, error) {
+			rawURL := params[0].(string)
+
+			url, err := url.Parse(rawURL)
+			if err != nil {
+				return false, errors.WithStack(err)
+			}
+
+			r.URL = url
+
+			return true, nil
+		},
+		new(func(string) bool),
+	)
+}
+
+func addRequestHeaderFunc(r *http.Request) expr.Option {
+	return expr.Function(
+		"add_header",
+		func(params ...any) (any, error) {
+			name := params[0].(string)
+			rawValue := params[1]
+
+			var value string
+			switch v := rawValue.(type) {
+			case []string:
+				value = strings.Join(v, ",")
+			case time.Time:
+				value = strconv.FormatInt(v.UTC().Unix(), 10)
+			case time.Duration:
+				value = strconv.FormatInt(int64(v.Seconds()), 10)
+			default:
+				value = fmt.Sprintf("%v", rawValue)
+			}
+
+			r.Header.Add(name, value)
+
+			return true, nil
+		},
+		new(func(string, string) bool),
+	)
+}
+
+func setRequestHeaderFunc(r *http.Request) expr.Option {
+	return expr.Function(
+		"set_header",
+		func(params ...any) (any, error) {
+			name := params[0].(string)
+			rawValue := params[1]
+
+			var value string
+			switch v := rawValue.(type) {
+			case []string:
+				value = strings.Join(v, ",")
+			case time.Time:
+				value = strconv.FormatInt(v.UTC().Unix(), 10)
+			case time.Duration:
+				value = strconv.FormatInt(int64(v.Seconds()), 10)
+			default:
+				value = fmt.Sprintf("%v", rawValue)
+			}
+
+			r.Header.Set(name, value)
+
+			return true, nil
+		},
+		new(func(string, string) bool),
+	)
+}
+
+func delRequestHeadersFunc(r *http.Request) expr.Option {
+	return expr.Function(
+		"del_headers",
+		func(params ...any) (any, error) {
+			pattern := params[0].(string)
+			deleted := false
+
+			for key := range r.Header {
+				if !wildcard.Match(key, pattern) {
+					continue
+				}
+
+				r.Header.Del(key)
+				deleted = true
+			}
+
+			return deleted, nil
+		},
+		new(func(string) bool),
+	)
+}

internal/rule/http/response.go

@@ -0,0 +1,88 @@
+package http
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"forge.cadoles.com/Cadoles/go-proxy/wildcard"
+	"github.com/expr-lang/expr"
+)
+
+func addResponseHeaderFunc(r *http.Response) expr.Option {
+	return expr.Function(
+		"add_header",
+		func(params ...any) (any, error) {
+			name := params[0].(string)
+			rawValue := params[1]
+
+			var value string
+			switch v := rawValue.(type) {
+			case []string:
+				value = strings.Join(v, ",")
+			case time.Time:
+				value = strconv.FormatInt(v.UTC().Unix(), 10)
+			case time.Duration:
+				value = strconv.FormatInt(int64(v.Seconds()), 10)
+			default:
+				value = fmt.Sprintf("%v", rawValue)
+			}
+
+			r.Header.Add(name, value)
+
+			return true, nil
+		},
+		new(func(string, string) bool),
+	)
+}
+
+func setResponseHeaderFunc(r *http.Response) expr.Option {
+	return expr.Function(
+		"set_header",
+		func(params ...any) (any, error) {
+			name := params[0].(string)
+			rawValue := params[1]
+
+			var value string
+			switch v := rawValue.(type) {
+			case []string:
+				value = strings.Join(v, ",")
+			case time.Time:
+				value = strconv.FormatInt(v.UTC().Unix(), 10)
+			case time.Duration:
+				value = strconv.FormatInt(int64(v.Seconds()), 10)
+			default:
+				value = fmt.Sprintf("%v", rawValue)
+			}
+
+			r.Header.Set(name, value)
+
+			return true, nil
+		},
+		new(func(string, string) bool),
+	)
+}
+
+func delResponseHeadersFunc(r *http.Response) expr.Option {
+	return expr.Function(
+		"del_headers",
+		func(params ...any) (any, error) {
+			pattern := params[0].(string)
+			deleted := false
+
+			for key := range r.Header {
+				if !wildcard.Match(key, pattern) {
+					continue
+				}
+
+				r.Header.Del(key)
+				deleted = true
+			}
+
+			return deleted, nil
+		},
+		new(func(string) bool),
+	)
+}

internal/rule/options.go

@@ -0,0 +1,35 @@
+package rule
+
+import "github.com/expr-lang/expr"
+
+type Options struct {
+	Rules []string
+	Expr  []expr.Option
+}
+
+type OptionFunc func(opts *Options)
+
+func NewOptions(funcs ...OptionFunc) *Options {
+	opts := &Options{
+		Expr:  make([]expr.Option, 0),
+		Rules: make([]string, 0),
+	}
+
+	for _, fn := range funcs {
+		fn(opts)
+	}
+
+	return opts
+}
+
+func WithRules(rules ...string) OptionFunc {
+	return func(opts *Options) {
+		opts.Rules = rules
+	}
+}
+
+func WithExpr(options ...expr.Option) OptionFunc {
+	return func(opts *Options) {
+		opts.Expr = options
+	}
+}