package api

import (
	"errors"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"time"

	"github.com/go-chi/chi/v5"

	"github.com/cdnutter/playlink/internal/backup"
	"github.com/cdnutter/playlink/internal/store"
)

func (s *Server) backupRoutes(r chi.Router) {
	r.Get("/backups", s.handleListBackups)
	r.Put("/backups/config", s.handleBackupConfig)
	r.Post("/backups", s.handleCreateBackup)
	r.Post("/backups/restore-upload", s.handleRestoreUpload)
	r.Get("/backups/{name}/download", s.handleDownloadBackup)
	r.Post("/backups/{name}/restore", s.handleRestoreBackup)
	r.Delete("/backups/{name}", s.handleDeleteBackup)
}

func (s *Server) handleListBackups(w http.ResponseWriter, r *http.Request) {
	list, err := s.cfg.Backups.List(r.Context())
	if err != nil {
		writeErr(w, 500, err)
		return
	}
	writeJSON(w, 200, map[string]any{"config": s.cfg.Backups.Config(r.Context()), "backups": list})
}

func (s *Server) handleBackupConfig(w http.ResponseWriter, r *http.Request) {
	var c backup.Config
	if !readJSON(w, r, &c) {
		return
	}
	if err := s.cfg.Backups.SetConfig(r.Context(), c); err != nil {
		writeErr(w, 400, err)
		return
	}
	writeJSON(w, 200, s.cfg.Backups.Config(r.Context()))
}

func (s *Server) handleCreateBackup(w http.ResponseWriter, r *http.Request) {
	b, err := s.cfg.Backups.Create(r.Context(), backup.TypeManual, "manual")
	if err != nil {
		writeErr(w, 500, err)
		return
	}
	writeJSON(w, 200, b)
}

func (s *Server) backupPath(w http.ResponseWriter, r *http.Request) (string, bool) {
	p, err := s.cfg.Backups.Path(r.Context(), chi.URLParam(r, "name"))
	switch {
	case errors.Is(err, backup.ErrBadName):
		writeErr(w, 400, err)
	case err != nil:
		writeErr(w, 404, errors.New("backup not found"))
	default:
		return p, true
	}
	return "", false
}

func (s *Server) handleDownloadBackup(w http.ResponseWriter, r *http.Request) {
	p, ok := s.backupPath(w, r)
	if !ok {
		return
	}
	w.Header().Set("Content-Type", "application/zip")
	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, filepath.Base(p)))
	http.ServeFile(w, r, p)
}

func (s *Server) handleDeleteBackup(w http.ResponseWriter, r *http.Request) {
	if _, ok := s.backupPath(w, r); !ok {
		return
	}
	if err := s.cfg.Backups.Delete(r.Context(), chi.URLParam(r, "name")); err != nil {
		writeErr(w, 500, err)
		return
	}
	writeJSON(w, 200, map[string]any{"ok": true})
}

// restoreBusy refuses a restore while any job runs: the database is about to
// be replaced.
func (s *Server) restoreBusy(w http.ResponseWriter, r *http.Request) bool {
	pairs, _ := s.st.Pairs(r.Context())
	for _, p := range pairs {
		if j := s.eng.Job(p.ID); j != nil && j.State == "running" {
			writeErr(w, 409, fmt.Errorf("a job is running for %q; wait for it to finish before restoring", p.Name))
			return true
		}
	}
	return false
}

func (s *Server) handleRestoreBackup(w http.ResponseWriter, r *http.Request) {
	p, ok := s.backupPath(w, r)
	if !ok || s.restoreBusy(w, r) {
		return
	}
	s.stageAndRestart(w, r, p)
}

func (s *Server) handleRestoreUpload(w http.ResponseWriter, r *http.Request) {
	if s.restoreBusy(w, r) {
		return
	}
	file, _, err := r.FormFile("backup")
	if err != nil {
		writeErr(w, 400, errors.New("choose a backup .zip file to upload"))
		return
	}
	defer file.Close()
	tmp, err := os.CreateTemp(s.cfg.Backups.Config(r.Context()).Folder, ".upload-*.zip")
	if err != nil {
		writeErr(w, 500, err)
		return
	}
	defer os.Remove(tmp.Name())
	if _, err := io.Copy(tmp, file); err != nil {
		tmp.Close()
		writeErr(w, 400, err)
		return
	}
	tmp.Close()
	s.stageAndRestart(w, r, tmp.Name())
}

func (s *Server) stageAndRestart(w http.ResponseWriter, r *http.Request, zipPath string) {
	if err := s.cfg.Backups.Stage(r.Context(), zipPath, store.SchemaVersion()); err != nil {
		writeErr(w, 400, err)
		return
	}
	writeJSON(w, 202, map[string]any{"ok": true, "restarting": true})
	if s.cfg.Restart != nil {
		// Let the response reach the browser before shutting down.
		go func() {
			time.Sleep(500 * time.Millisecond)
			s.log.Warn("restarting to apply the restored backup")
			s.cfg.Restart()
		}()
	}
}