package web

import (
	"context"
	"errors"
	"net/http"
	"strconv"
	"strings"

	"github.com/m/projax/gitea"
	"github.com/m/projax/store"
)

// handleIssueAction dispatches POST /i/{path}/issues/{action} where action is
// close|reopen|comment|create. Form fields: repo (owner/repo), number
// (optional for create), body (optional for create/comment).
//
// On success the handler busts the dashboard cache and re-renders the
// detail-page issues_section partial so HTMX swaps it into place.
func (s *Server) handleIssueAction(w http.ResponseWriter, r *http.Request, path, action string) {
	if s.Gitea == nil {
		http.Error(w, "gitea not configured", http.StatusServiceUnavailable)
		return
	}
	it, err := s.Store.GetByPath(r.Context(), path)
	if err != nil {
		s.fail(w, r, err)
		return
	}
	if err := r.ParseForm(); err != nil {
		s.fail(w, r, err)
		return
	}
	repoRef := strings.TrimSpace(r.FormValue("repo"))
	if repoRef == "" {
		http.Error(w, "repo required", http.StatusBadRequest)
		return
	}
	// Guard: repo must be linked to this item.
	if !s.repoLinkedToItem(r.Context(), it.ID, repoRef) {
		http.Error(w, "repo not linked to this item", http.StatusForbidden)
		return
	}
	owner, repo := gitea.ParseRepoRef(repoRef)
	if owner == "" || repo == "" {
		http.Error(w, "malformed repo ref", http.StatusBadRequest)
		return
	}

	banner := ""
	switch action {
	case "close":
		num, ok := parseIssueNumber(r.FormValue("number"))
		if !ok {
			http.Error(w, "number required", http.StatusBadRequest)
			return
		}
		if err := s.Gitea.Client.CloseIssue(r.Context(), owner, repo, num); err != nil {
			banner = giteaWritebackBanner("close", repoRef, err)
		}
	case "reopen":
		num, ok := parseIssueNumber(r.FormValue("number"))
		if !ok {
			http.Error(w, "number required", http.StatusBadRequest)
			return
		}
		if err := s.Gitea.Client.ReopenIssue(r.Context(), owner, repo, num); err != nil {
			banner = giteaWritebackBanner("reopen", repoRef, err)
		}
	case "comment":
		num, ok := parseIssueNumber(r.FormValue("number"))
		if !ok {
			http.Error(w, "number required", http.StatusBadRequest)
			return
		}
		body := strings.TrimSpace(r.FormValue("body"))
		if body == "" {
			banner = "Cannot post empty comment."
			break
		}
		if _, err := s.Gitea.Client.AddComment(r.Context(), owner, repo, num, body); err != nil {
			banner = giteaWritebackBanner("comment", repoRef, err)
		}
	case "create":
		title := strings.TrimSpace(r.FormValue("title"))
		if title == "" {
			banner = "Cannot create issue without a title."
			break
		}
		body := r.FormValue("body")
		if _, err := s.Gitea.Client.CreateIssue(r.Context(), owner, repo, title, body); err != nil {
			banner = giteaWritebackBanner("create", repoRef, err)
		}
	default:
		http.Error(w, "unknown action: "+action, http.StatusBadRequest)
		return
	}

	// Bust caches so the next fetch reflects the upstream change.
	s.Gitea.Cache.Invalidate(repoRef + "|open")
	s.Gitea.Cache.Invalidate(repoRef + "|closed-recent")
	if s.dashboard != nil {
		s.dashboard.InvalidateAll()
	}

	if r.Header.Get("HX-Request") == "true" {
		s.renderIssuesSection(w, r, it, banner)
		return
	}
	http.Redirect(w, r, "/i/"+it.PrimaryPath(), http.StatusSeeOther)
}

// renderIssuesSection re-fetches the issues for the item and renders the
// issues_section partial. Used by HTMX swaps after a writeback.
func (s *Server) renderIssuesSection(w http.ResponseWriter, r *http.Request, it *store.Item, banner string) {
	issues, err := s.detailIssues(r.Context(), it)
	if err != nil {
		s.fail(w, r, err)
		return
	}
	openTotal := 0
	for _, ri := range issues {
		openTotal += ri.OpenCount
	}
	s.render(w, r, "issues_section", map[string]any{
		"Item":            it,
		"Issues":          issues,
		"IssuesOpenTotal": openTotal,
		"GiteaOn":         s.Gitea != nil,
		"Banner":          banner,
	})
}

// repoLinkedToItem checks that the given owner/repo ref is actually attached
// to this item via a gitea-repo item_link. Prevents form-crafted writeback
// against unrelated repos.
func (s *Server) repoLinkedToItem(ctx context.Context, itemID, repoRef string) bool {
	links, err := s.Store.LinksByType(ctx, itemID, refTypeGiteaRepo)
	if err != nil {
		return false
	}
	for _, l := range links {
		if l.RefID == repoRef {
			return true
		}
	}
	return false
}

func parseIssueNumber(s string) (int, bool) {
	n, err := strconv.Atoi(strings.TrimSpace(s))
	if err != nil || n <= 0 {
		return 0, false
	}
	return n, true
}

// giteaWritebackBanner formats an inline error banner so the issues section
// surfaces upstream failures (token lacks perms, repo not found, network)
// without breaking the page render.
func giteaWritebackBanner(action, repo string, err error) string {
	switch {
	case errors.Is(err, gitea.ErrForbidden):
		return "Could not " + action + " on " + repo + ": Gitea token lacks write access. Check GITEA_TOKEN_AI scope."
	case errors.Is(err, gitea.ErrNotFound):
		return "Repo " + repo + " not found on Gitea (renamed, deleted, or token lacks access)."
	}
	return "Could not " + action + " issue on " + repo + ": " + err.Error()
}

// Server.repoLinkedToItem requires the handler to pass r.Context(); the
// signature is plain context.Context so package importers (tests, other web
// helpers) don't need to know which package the context came from.