package proxy

import (
	"embed"
	"net/http"
	"strings"

	"code.wejust.rest/lain/ghproxy/internal/config"
	"github.com/gin-gonic/gin"
)

//go:embed static/index.html
var staticFS embed.FS

type ProxyHandler struct {
	addr         string
	githubProxy  http.Handler
	assetsProxy  http.Handler
	apiProxy     http.Handler
	allowedRepos map[string]bool
}

func NewProxyHandler(cfg *config.Config) (*ProxyHandler, error) {
	allowed := make(map[string]bool)
	for _, repo := range cfg.AllowedRepos {
		allowed[repo] = true
	}

	return &ProxyHandler{
		addr:         cfg.Addr,
		githubProxy:  CreateReverseProxy("https://github.com"),
		assetsProxy:  CreateReverseProxy("https://github.githubassets.com"),
		apiProxy:     CreateReverseProxy("https://api.github.com"),
		allowedRepos: allowed,
	}, nil
}

func (h *ProxyHandler) RegisterRoutes(r *gin.Engine) {
	r.GET("/", func(c *gin.Context) {
		if c.Request.URL.Path == "/" {
			data, err := staticFS.ReadFile("static/index.html")
			if err != nil {
				c.String(http.StatusInternalServerError, "failed to read embedded index.html")
				return
			}
			c.Data(http.StatusOK, "text/html; charset=utf-8", data)
			return
		}
		c.Next()
	})

	r.GET("/robots.txt", func(c *gin.Context) {
		c.Data(http.StatusOK, "text/plain; charset=utf-8", []byte("User-Agent: *\nDisallow: /\n"))
	})

	r.NoRoute(func(c *gin.Context) {
		reqPath := c.Request.URL.Path

		if strings.Contains(reqPath, "/_private/browser/stats") {
			c.AbortWithStatus(http.StatusNoContent)
			return
		}

		//NOTE(kroot): proxy GitHub GraphQL API as-is to avoid breaking the issues UI
		if reqPath == "/_graphql" {
			h.githubProxy.ServeHTTP(c.Writer, c.Request)
			return
		}

		//NOTE(kroot): handle assets, gravatars, and favicons
		if strings.Contains(reqPath, "/assets/") || strings.HasPrefix(reqPath, "/images/gravatars/") || strings.HasPrefix(reqPath, "/favicons/") {
			h.assetsProxy.ServeHTTP(c.Writer, c.Request)
			return
		}

		if strings.HasPrefix(reqPath, "/api/") {
			//NOTE(kroot): strip /api prefix if needed, or just proxy as is
			h.apiProxy.ServeHTTP(c.Writer, c.Request)
			return
		}

		parts := strings.Split(strings.Trim(reqPath, "/"), "/")

		//NOTE(kroot): if we have allowed_repos, restrict access
		if len(h.allowedRepos) > 0 {
			if len(parts) >= 2 {
				repoFullName := parts[0] + "/" + parts[1]
				if h.allowedRepos[repoFullName] {
					h.serveWithCache(c.Writer, c.Request, h.githubProxy)
					return
				}
			}

			//NOTE(kroot): if its not an allowed repository, and allowed_repos is not empty, just redirect to root
			c.Redirect(http.StatusSeeOther, "/")
			return
		}

		//NOTE(kroot): if allowed_repos is empty, allow everything
		h.serveWithCache(c.Writer, c.Request, h.githubProxy)
	})
}