package proxy

import (
	"encoding/json"
	"io"
	"net/http"
	"net/url"
	"time"

	"forgejo.riotpiao.com/rock/homelab-frontend/internal/logging"
)

// tokenRequest is the JSON body for POST /auth/token.
type tokenRequest struct {
	Username string `json:"username"`
	Password string `json:"password"`
	Scope    string `json:"scope,omitempty"`
}

// refreshRequest is the JSON body for POST /auth/refresh.
type refreshRequest struct {
	RefreshToken string `json:"refresh_token"`
	Scope        string `json:"scope,omitempty"`
}

// authClient handles token exchange with the upstream identity provider.
// Extracted for testability — production uses http.DefaultClient,
// tests inject a stub.
type authClient interface {
	PostForm(url string, data url.Values) (*http.Response, error)
}

// httpAuthClient wraps http.Client to implement authClient.
type httpAuthClient struct {
	client *http.Client
}

func (c *httpAuthClient) PostForm(url string, data url.Values) (*http.Response, error) {
	return c.client.PostForm(url, data)
}

func newAuthClient() authClient {
	return &httpAuthClient{
		client: &http.Client{Timeout: 10 * time.Second},
	}
}

// handleAuthToken exchanges username+password for a JWT via the upstream
// identity provider's token endpoint using grant_type=password.
func (h *Handler) handleAuthToken(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		writeProblemDetail(w, http.StatusMethodNotAllowed,
			"about:blank#method-not-allowed", "Method Not Allowed",
			"POST only", nil)
		return
	}

	if h.config.Auth.TokenURL == "" || h.config.Auth.ClientID == "" {
		writeProblemDetail(w, http.StatusServiceUnavailable,
			"about:blank#not-configured", "Not Configured",
			"token endpoint not configured", nil)
		return
	}

	var req tokenRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeProblemDetail(w, http.StatusBadRequest,
			"about:blank#bad-request", "Bad Request",
			"invalid JSON body", nil)
		return
	}

	if req.Username == "" || req.Password == "" {
		writeProblemDetail(w, http.StatusBadRequest,
			"about:blank#bad-request", "Bad Request",
			"username and password are required", nil)
		return
	}

	scope := req.Scope
	if scope == "" {
		scope = "openid roles permissions"
	}

	form := url.Values{
		"grant_type":    {"password"},
		"username":      {req.Username},
		"password":      {req.Password},
		"client_id":     {h.config.Auth.ClientID},
		"client_secret": {h.config.Auth.ClientSecret},
		"scope":         {scope},
	}

	h.forwardTokenResponse(w, form, "/auth/token")
}

// handleAuthRefresh exchanges a refresh token for a new JWT.
func (h *Handler) handleAuthRefresh(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		writeProblemDetail(w, http.StatusMethodNotAllowed,
			"about:blank#method-not-allowed", "Method Not Allowed",
			"POST only", nil)
		return
	}

	if h.config.Auth.TokenURL == "" || h.config.Auth.ClientID == "" {
		writeProblemDetail(w, http.StatusServiceUnavailable,
			"about:blank#not-configured", "Not Configured",
			"token endpoint not configured", nil)
		return
	}

	var req refreshRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeProblemDetail(w, http.StatusBadRequest,
			"about:blank#bad-request", "Bad Request",
			"invalid JSON body", nil)
		return
	}

	if req.RefreshToken == "" {
		writeProblemDetail(w, http.StatusBadRequest,
			"about:blank#bad-request", "Bad Request",
			"refresh_token is required", nil)
		return
	}

	form := url.Values{
		"grant_type":    {"refresh_token"},
		"refresh_token": {req.RefreshToken},
		"client_id":     {h.config.Auth.ClientID},
		"client_secret": {h.config.Auth.ClientSecret},
	}

	if req.Scope != "" {
		form.Set("scope", req.Scope)
	}

	h.forwardTokenResponse(w, form, "/auth/refresh")
}

// forwardTokenResponse posts form data to the token endpoint and
// forwards the response verbatim to the client.
func (h *Handler) forwardTokenResponse(w http.ResponseWriter, form url.Values, logPath string) {
	resp, err := h.authHTTP.PostForm(h.config.Auth.TokenURL, form)
	if err != nil {
		writeProblemDetail(w, http.StatusBadGateway,
			"about:blank#bad-gateway", "Bad Gateway",
			"identity provider unreachable", nil)
		logging.Errorf("auth upstream error", err, map[string]string{
			"path": logPath,
		})
		return
	}
	defer resp.Body.Close()

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(resp.StatusCode)
	io.Copy(w, resp.Body)
}