package autorest

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"strings"
)

const (
	mimeTypeJSON     = "application/json"
	mimeTypeFormPost = "application/x-www-form-urlencoded"

	headerAuthorization = "Authorization"
	headerContentType   = "Content-Type"
	headerUserAgent     = "User-Agent"
)

// Preparer is the interface that wraps the Prepare method.
//
// Prepare accepts and possibly modifies an http.Request (e.g., adding Headers). Implementations
// must ensure to not share or hold per-invocation state since Preparers may be shared and re-used.
type Preparer interface {
	Prepare(*http.Request) (*http.Request, error)
}

// PreparerFunc is a method that implements the Preparer interface.
type PreparerFunc func(*http.Request) (*http.Request, error)

// Prepare implements the Preparer interface on PreparerFunc.
func (pf PreparerFunc) Prepare(r *http.Request) (*http.Request, error) {
	return pf(r)
}

// PrepareDecorator takes and possibly decorates, by wrapping, a Preparer. Decorators may affect the
// http.Request and pass it along or, first, pass the http.Request along then affect the result.
type PrepareDecorator func(Preparer) Preparer

// CreatePreparer creates, decorates, and returns a Preparer.
// Without decorators, the returned Preparer returns the passed http.Request unmodified.
// Preparers are safe to share and re-use.
func CreatePreparer(decorators ...PrepareDecorator) Preparer {
	return DecoratePreparer(
		Preparer(PreparerFunc(func(r *http.Request) (*http.Request, error) { return r, nil })),
		decorators...)
}

// DecoratePreparer accepts a Preparer and a, possibly empty, set of PrepareDecorators, which it
// applies to the Preparer. Decorators are applied in the order received, but their affect upon the
// request depends on whether they are a pre-decorator (change the http.Request and then pass it
// along) or a post-decorator (pass the http.Request along and alter it on return).
func DecoratePreparer(p Preparer, decorators ...PrepareDecorator) Preparer {
	for _, decorate := range decorators {
		p = decorate(p)
	}
	return p
}

// Prepare accepts an http.Request and a, possibly empty, set of PrepareDecorators.
// It creates a Preparer from the decorators which it then applies to the passed http.Request.
func Prepare(r *http.Request, decorators ...PrepareDecorator) (*http.Request, error) {
	if r == nil {
		return nil, NewError("autorest", "Prepare", "Invoked without an http.Request")
	}
	return CreatePreparer(decorators...).Prepare(r)
}

// WithNothing returns a "do nothing" PrepareDecorator that makes no changes to the passed
// http.Request.
func WithNothing() PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			return p.Prepare(r)
		})
	}
}

// WithHeader returns a PrepareDecorator that sets the specified HTTP header of the http.Request to
// the passed value. It canonicalizes the passed header name (via http.CanonicalHeaderKey) before
// adding the header.
func WithHeader(header string, value string) PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				if r.Header == nil {
					r.Header = make(http.Header)
				}
				r.Header.Set(http.CanonicalHeaderKey(header), value)
			}
			return r, err
		})
	}
}

// WithBearerAuthorization returns a PrepareDecorator that adds an HTTP Authorization header whose
// value is "Bearer " followed by the supplied token.
func WithBearerAuthorization(token string) PrepareDecorator {
	return WithHeader(headerAuthorization, fmt.Sprintf("Bearer %s", token))
}

// AsContentType returns a PrepareDecorator that adds an HTTP Content-Type header whose value
// is the passed contentType.
func AsContentType(contentType string) PrepareDecorator {
	return WithHeader(headerContentType, contentType)
}

// WithUserAgent returns a PrepareDecorator that adds an HTTP User-Agent header whose value is the
// passed string.
func WithUserAgent(ua string) PrepareDecorator {
	return WithHeader(headerUserAgent, ua)
}

// AsFormURLEncoded returns a PrepareDecorator that adds an HTTP Content-Type header whose value is
// "application/x-www-form-urlencoded".
func AsFormURLEncoded() PrepareDecorator {
	return AsContentType(mimeTypeFormPost)
}

// AsJSON returns a PrepareDecorator that adds an HTTP Content-Type header whose value is
// "application/json".
func AsJSON() PrepareDecorator {
	return AsContentType(mimeTypeJSON)
}

// WithMethod returns a PrepareDecorator that sets the HTTP method of the passed request. The
// decorator does not validate that the passed method string is a known HTTP method.
func WithMethod(method string) PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r.Method = method
			return p.Prepare(r)
		})
	}
}

// AsDelete returns a PrepareDecorator that sets the HTTP method to DELETE.
func AsDelete() PrepareDecorator { return WithMethod("DELETE") }

// AsGet returns a PrepareDecorator that sets the HTTP method to GET.
func AsGet() PrepareDecorator { return WithMethod("GET") }

// AsHead returns a PrepareDecorator that sets the HTTP method to HEAD.
func AsHead() PrepareDecorator { return WithMethod("HEAD") }

// AsOptions returns a PrepareDecorator that sets the HTTP method to OPTIONS.
func AsOptions() PrepareDecorator { return WithMethod("OPTIONS") }

// AsPatch returns a PrepareDecorator that sets the HTTP method to PATCH.
func AsPatch() PrepareDecorator { return WithMethod("PATCH") }

// AsPost returns a PrepareDecorator that sets the HTTP method to POST.
func AsPost() PrepareDecorator { return WithMethod("POST") }

// AsPut returns a PrepareDecorator that sets the HTTP method to PUT.
func AsPut() PrepareDecorator { return WithMethod("PUT") }

// WithBaseURL returns a PrepareDecorator that populates the http.Request with a url.URL constructed
// from the supplied baseUrl.
func WithBaseURL(baseURL string) PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				var u *url.URL
				u, err = url.Parse(baseURL)
				if u.Scheme == "" {
					err = fmt.Errorf("autorest: No scheme detected in URL %s", baseURL)
				}
				if err == nil {
					r.URL = u
				}
			}
			return r, err
		})
	}
}

// WithFormData returns a PrepareDecoratore that "URL encodes" (e.g., bar=baz&foo=quux) into the
// http.Request body.
func WithFormData(v url.Values) PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				s := v.Encode()
				r.ContentLength = int64(len(s))
				r.Body = ioutil.NopCloser(strings.NewReader(s))
			}
			return r, err
		})
	}
}

// WithBool returns a PrepareDecorator that encodes the passed bool into the body of the request
// and sets the Content-Length header.
func WithBool(v bool) PrepareDecorator {
	return WithString(fmt.Sprintf("%v", v))
}

// WithFloat32 returns a PrepareDecorator that encodes the passed float32 into the body of the
// request and sets the Content-Length header.
func WithFloat32(v float32) PrepareDecorator {
	return WithString(fmt.Sprintf("%v", v))
}

// WithFloat64 returns a PrepareDecorator that encodes the passed float64 into the body of the
// request and sets the Content-Length header.
func WithFloat64(v float64) PrepareDecorator {
	return WithString(fmt.Sprintf("%v", v))
}

// WithInt32 returns a PrepareDecorator that encodes the passed int32 into the body of the request
// and sets the Content-Length header.
func WithInt32(v int32) PrepareDecorator {
	return WithString(fmt.Sprintf("%v", v))
}

// WithInt64 returns a PrepareDecorator that encodes the passed int64 into the body of the request
// and sets the Content-Length header.
func WithInt64(v int64) PrepareDecorator {
	return WithString(fmt.Sprintf("%v", v))
}

// WithString returns a PrepareDecorator that encodes the passed string into the body of the request
// and sets the Content-Length header.
func WithString(v string) PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				r.ContentLength = int64(len(v))
				r.Body = ioutil.NopCloser(strings.NewReader(v))
			}
			return r, err
		})
	}
}

// WithJSON returns a PrepareDecorator that encodes the data passed as JSON into the body of the
// request and sets the Content-Length header.
func WithJSON(v interface{}) PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				b, err := json.Marshal(v)
				if err == nil {
					r.ContentLength = int64(len(b))
					r.Body = ioutil.NopCloser(bytes.NewReader(b))
				}
			}
			return r, err
		})
	}
}

// WithPath returns a PrepareDecorator that adds the supplied path to the request URL. If the path
// is absolute (that is, it begins with a "/"), it replaces the existing path.
func WithPath(path string) PrepareDecorator {
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				if r.URL == nil {
					return r, NewError("autorest", "WithPath", "Invoked with a nil URL")
				}
				u := r.URL
				u.Path = strings.TrimRight(u.Path, "/")
				if strings.HasPrefix(path, "/") {
					u.Path = path
				} else {
					u.Path += "/" + path
				}
			}
			return r, err
		})
	}
}

// WithEscapedPathParameters returns a PrepareDecorator that replaces brace-enclosed keys within the
// request path (i.e., http.Request.URL.Path) with the corresponding values from the passed map. The
// values will be escaped (aka URL encoded) before insertion into the path.
func WithEscapedPathParameters(pathParameters map[string]interface{}) PrepareDecorator {
	parameters := escapeValueStrings(ensureValueStrings(pathParameters))
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				if r.URL == nil {
					return r, NewError("autorest", "WithEscapedPathParameters", "Invoked with a nil URL")
				}
				for key, value := range parameters {
					r.URL.Path = strings.Replace(r.URL.Path, "{"+key+"}", value, -1)
				}
			}
			return r, err
		})
	}
}

// WithPathParameters returns a PrepareDecorator that replaces brace-enclosed keys within the
// request path (i.e., http.Request.URL.Path) with the corresponding values from the passed map.
func WithPathParameters(pathParameters map[string]interface{}) PrepareDecorator {
	parameters := ensureValueStrings(pathParameters)
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				if r.URL == nil {
					return r, NewError("autorest", "WithPathParameters", "Invoked with a nil URL")
				}
				for key, value := range parameters {
					r.URL.Path = strings.Replace(r.URL.Path, "{"+key+"}", value, -1)
				}
			}
			return r, err
		})
	}
}

// WithQueryParameters returns a PrepareDecorators that encodes and applies the query parameters
// given in the supplied map (i.e., key=value).
func WithQueryParameters(queryParameters map[string]interface{}) PrepareDecorator {
	parameters := ensureValueStrings(queryParameters)
	return func(p Preparer) Preparer {
		return PreparerFunc(func(r *http.Request) (*http.Request, error) {
			r, err := p.Prepare(r)
			if err == nil {
				if r.URL == nil {
					return r, NewError("autorest", "WithQueryParameters", "Invoked with a nil URL")
				}
				v := r.URL.Query()
				for key, value := range parameters {
					v.Add(key, value)
				}
				r.URL.RawQuery = v.Encode()
			}
			return r, err
		})
	}
}

// Authorizer is the interface that provides a PrepareDecorator used to supply request
// authorization. Most often, the Authorizer decorator runs last so it has access to the full
// state of the formed HTTP request.
type Authorizer interface {
	WithAuthorization() PrepareDecorator
}

// NullAuthorizer implements a default, "do nothing" Authorizer.
type NullAuthorizer struct{}

// WithAuthorization returns a PrepareDecorator that does nothing.
func (na NullAuthorizer) WithAuthorization() PrepareDecorator {
	return WithNothing()
}
