package api

import (
	structs "code.gitea.io/gitea/modules/structs"
	gitea "code.gitea.io/sdk/gitea"
	"encoding/json"
	"fmt"
	"git.lumeweb.com/LumeWeb/gitea-github-proxy/config"
	"github.com/google/go-github/v59/github"
	"github.com/gorilla/mux"
	"go.uber.org/zap"
	"net/http"
	"strconv"
)

type restApi struct {
	config *config.Config
	logger *zap.Logger
}

func newRestApi(cfg *config.Config, logger *zap.Logger) *restApi {
	return &restApi{config: cfg, logger: logger}
}

func (r restApi) handlerGetPullRequestFiles(w http.ResponseWriter, request *http.Request) {
	vars := mux.Vars(request)

	owner := vars["owner"]
	repo := vars["repo"]
	pullNumber := vars["pull_number"]

	client := r.getClientOrError(w)

	if client == nil {
		return
	}
	parsedPullNumber, err := strconv.ParseInt(pullNumber, 10, 64)
	if err != nil {
		http.Error(w, "Failed to parse pull number", http.StatusBadRequest)
		r.logger.Error("Failed to parse pull number", zap.Error(err))
		return
	}

	files, r2, err := client.ListPullRequestFiles(owner, repo, parsedPullNumber, gitea.ListPullRequestFilesOptions{
		ListOptions: r.getPagingOptions(request),
	})
	if err != nil {
		http.Error(w, "Failed to get pull request files", http.StatusInternalServerError)
		r.logger.Error("Failed to get pull request files", zap.Error(err))
		return
	}

	githubFiles := make([]*github.CommitFile, len(files))

	for i, file := range files {
		f := structs.ChangedFile(*file)
		githubFiles[i] = convertCommitFile(&f)
	}

	r.sendPagingHeaders(w, r2)
	r.respond(w, http.StatusOK, githubFiles)
}

func (r restApi) getPagingOptions(request *http.Request) gitea.ListOptions {
	page, _ := strconv.Atoi(request.URL.Query().Get("page"))
	perPage, _ := strconv.Atoi(request.URL.Query().Get("per_page"))

	return gitea.ListOptions{
		Page:     page,
		PageSize: perPage,
	}
}

func (r restApi) sendPagingHeaders(w http.ResponseWriter, apiResponse *gitea.Response) {
	links := []string{}

	baseURL := fmt.Sprintf("https://%s", r.config.Domain)

	joinStrings := func(elements []string, separator string) string {
		if len(elements) == 0 {
			return ""
		}
		result := elements[0]
		for i := 1; i < len(elements); i++ {
			result += separator + elements[i]
		}
		return result
	}
	joinLinks := func(links []string) string {
		return fmt.Sprintf("%s", joinStrings(links, ", "))
	}

	if apiResponse.FirstPage > 0 {
		links = append(links, fmt.Sprintf(`<%s?page=%d>; rel="first"`, baseURL, apiResponse.FirstPage))
	}
	if apiResponse.PrevPage > 0 {
		links = append(links, fmt.Sprintf(`<%s?page=%d>; rel="prev"`, baseURL, apiResponse.PrevPage))
	}
	if apiResponse.NextPage > 0 {
		links = append(links, fmt.Sprintf(`<%s?page=%d>; rel="next"`, baseURL, apiResponse.NextPage))
	}
	if apiResponse.LastPage > 0 {
		links = append(links, fmt.Sprintf(`<%s?page=%d>; rel="last"`, baseURL, apiResponse.LastPage))
	}

	if len(links) > 0 {
		w.Header().Add("Link", fmt.Sprintf("%s", joinLinks(links)))
	}
}

func (r restApi) respond(w http.ResponseWriter, status int, data interface{}) {
	jsonData, err := json.Marshal(data)
	if err != nil {
		http.Error(w, "Failed to marshal response", http.StatusInternalServerError)
		r.logger.Error("Failed to marshal response", zap.Error(err))
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if data != nil {
		_, _ = w.Write(jsonData)
	}
}

func (r restApi) getClientOrError(w http.ResponseWriter) *gitea.Client {
	client, err := getClient(ClientParams{
		Config: r.config,
	})
	if err != nil {
		http.Error(w, "Failed to get Gitea client", http.StatusInternalServerError)
		r.logger.Error("Failed to get Gitea client", zap.Error(err))
		return nil
	}

	return client
}

func setupRestRoutes(params RouteParams) {
	logger := params.Logger
	cfg := params.Config
	r := params.R

	restApi := newRestApi(cfg, logger)

	setupRoutes := func(r *mux.Router) {
		r.HandleFunc("/repos/{owner}/{repo}/pulls/{pull_number}/files", restApi.handlerGetPullRequestFiles).Methods("GET")
	}

	restRouter := r.PathPrefix("/api").Subrouter()
	restRouter.Use(githubRestVerifyMiddleware(params.Db))
	restRouter.Use(githubRestRequireAuthMiddleware(params.Config))

	setupRoutes(restRouter)
	setupRoutes(restRouter.PathPrefix("/v3").Subrouter())
}