package component

import (
	"context"
	"strings"

	"github.com/projectdiscovery/nuclei/v3/pkg/fuzz/dataformat"
	"github.com/projectdiscovery/retryablehttp-go"
)

// Header is a component for a request header
type Header struct {
	value *Value

	req *retryablehttp.Request
}

var _ Component = &Header{}

// NewHeader creates a new header component
func NewHeader() *Header {
	return &Header{}
}

// Name returns the name of the component
func (q *Header) Name() string {
	return RequestHeaderComponent
}

// Parse parses the component and returns the
// parsed component
func (q *Header) Parse(req *retryablehttp.Request) (bool, error) {
	q.req = req
	q.value = NewValue("")

	parsedHeaders := make(map[string]interface{})
	for key, value := range req.Header {
		if len(value) == 1 {
			parsedHeaders[key] = value[0]
			continue
		}
		parsedHeaders[key] = value
	}
	q.value.SetParsed(dataformat.KVMap(parsedHeaders), "")
	return true, nil
}

// Iterate iterates through the component
func (q *Header) Iterate(callback func(key string, value interface{}) error) (errx error) {
	q.value.parsed.Iterate(func(key string, value any) bool {
		// Skip ignored headers
		if _, ok := defaultIgnoredHeaderKeys[key]; ok {
			return ok
		}
		if err := callback(key, value); err != nil {
			errx = err
			return false
		}
		return true
	})
	return
}

// SetValue sets a value in the component
// for a key
func (q *Header) SetValue(key string, value string) error {
	if !q.value.SetParsedValue(key, value) {
		return ErrSetValue
	}
	return nil
}

// Delete deletes a key from the component
func (q *Header) Delete(key string) error {
	if !q.value.Delete(key) {
		return ErrKeyNotFound
	}
	return nil
}

// Rebuild returns a new request with the
// component rebuilt
func (q *Header) Rebuild() (*retryablehttp.Request, error) {
	cloned := q.req.Clone(context.Background())
	q.value.parsed.Iterate(func(key string, value any) bool {
		if strings.TrimSpace(key) == "" {
			return true
		}
		if strings.EqualFold(key, "Host") {
			return true
		}
		if vx, ok := IsTypedSlice(value); ok {
			// convert to []interface{}
			value = vx
		}
		if v, ok := value.([]interface{}); ok {
			for _, vv := range v {
				cloned.Header.Add(key, vv.(string))
			}
			return true
		}
		cloned.Header.Set(key, value.(string))
		return true
	})
	return cloned, nil
}

// Clones current state of this component
func (q *Header) Clone() Component {
	return &Header{
		value: q.value.Clone(),
		req:   q.req.Clone(context.Background()),
	}
}

// A list of headers that are essential to the request and
// must not be fuzzed.
var defaultIgnoredHeaderKeys = map[string]struct{}{
	"Accept-Charset":                   {},
	"Accept-Datetime":                  {},
	"Accept-Encoding":                  {},
	"Accept-Language":                  {},
	"Accept":                           {},
	"Access-Control-Request-Headers":   {},
	"Access-Control-Request-Method":    {},
	"Authorization":                    {},
	"Cache-Control":                    {},
	"Connection":                       {},
	"Cookie":                           {},
	"Content-Length":                   {},
	"Content-Type":                     {},
	"Date":                             {},
	"Dnt":                              {},
	"Expect":                           {},
	"Forwarded":                        {},
	"From":                             {},
	"Host":                             {},
	"If-Match":                         {},
	"If-Modified-Since":                {},
	"If-None-Match":                    {},
	"If-Range":                         {},
	"If-Unmodified-Since":              {},
	"Max-Forwards":                     {},
	"Pragma":                           {},
	"Priority":                         {},
	"Proxy-Authorization":              {},
	"Range":                            {},
	"Sec-Ch-Ua":                        {},
	"Sec-Ch-Ua-Mobile":                 {},
	"Sec-Ch-Ua-Platform":               {},
	"Sec-Fetch-Dest":                   {},
	"Sec-Fetch-Mode":                   {},
	"Sec-Fetch-Site":                   {},
	"Sec-Fetch-User":                   {},
	"TE":                               {},
	"Upgrade":                          {},
	"Via":                              {},
	"Warning":                          {},
	"Upgrade-Insecure-Requests":        {},
	"X-CSRF-Token":                     {},
	"X-Requested-With":                 {},
	"Strict-Transport-Security":        {},
	"Content-Security-Policy":          {},
	"X-Content-Type-Options":           {},
	"X-Frame-Options":                  {},
	"X-XSS-Protection":                 {},
	"Public-Key-Pins":                  {},
	"Referrer-Policy":                  {},
	"Access-Control-Allow-Origin":      {},
	"Access-Control-Allow-Credentials": {},
	"Access-Control-Expose-Headers":    {},
	"Access-Control-Max-Age":           {},
	"Access-Control-Allow-Methods":     {},
	"Access-Control-Allow-Headers":     {},
	"Server":                           {},
	"X-Powered-By":                     {},
	"X-AspNet-Version":                 {},
	"X-AspNetMvc-Version":              {},
	"ETag":                             {},
	"Vary":                             {},
	"Expires":                          {},
	"Last-Modified":                    {},
	"X-Cache":                          {},
	"X-Proxy-ID":                       {},
	"CF-Ray":                           {}, // Cloudflare
	"X-Served-By":                      {}, // Varnish, etc.
	"X-Cache-Hits":                     {},
	"Content-Encoding":                 {},
	"Transfer-Encoding":                {},
	"Location":                         {},
	"WWW-Authenticate":                 {},
	"Proxy-Authenticate":               {},
	"X-Access-Token":                   {},
	"X-Refresh-Token":                  {},
	"Link":                             {},
	"X-Content-Duration":               {},
	"X-UA-Compatible":                  {},
	"X-RateLimit-Limit":                {}, // Rate limiting header
	"X-RateLimit-Remaining":            {}, // Rate limiting header
	"X-RateLimit-Reset":                {}, // Rate limiting header
}