// Bulk triage actions for Phase 4 (FR-6, FR-9, FR-13).
//
// The UI selects rows in a group, then asks for delete, move, or mark. Two
// guard rails matter here:
//
//   - Deletes are recoverable: they move the message to the Delete label, never
//     a hard delete. A restore moves it back to INBOX.
//   - Spam is recommended, never auto-deleted. A delete that includes a message
//     classified Spam needs a second, explicit confirmation.
//
// Every action is appended to the action log.
package server

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

	"gitea.lab.audasmedia.com.au/sam/email_agent/internal/mailops"
	"gitea.lab.audasmedia.com.au/sam/email_agent/internal/store"
)

// MailActions is the mailbox side of a triage action. The live implementation is
// *mailops.Client; tests substitute a fake.
type MailActions interface {
	// Move files msg under destFolder and returns the Gmail label it now lives
	// in.
	Move(ctx context.Context, msg store.Message, destFolder string) (string, error)
	// Mark applies read/star flags (read, unread, star, unstar).
	Mark(ctx context.Context, msg store.Message, mark string) error
}

// handleBulkAction performs one action over the selected message ids.
func (s *Server) handleBulkAction(w http.ResponseWriter, r *http.Request) {
	if !s.csrfOK(r) {
		http.Error(w, "invalid CSRF token", http.StatusForbidden)
		return
	}
	if err := r.ParseForm(); err != nil {
		s.renderInbox(w, r, "", "Could not read the action form.")
		return
	}

	action := strings.ToLower(strings.TrimSpace(r.FormValue("action")))
	ids := parseIDList(r.Form["ids"])
	if len(ids) == 0 {
		s.renderInbox(w, r, "", "Select at least one message first.")
		return
	}

	ctx := r.Context()
	msgs, err := s.store.MessagesByIDs(ctx, ids)
	if err != nil {
		s.logger.Error("load selected messages", "error", err)
		s.renderInbox(w, r, "", "Could not load the selected messages.")
		return
	}
	if len(msgs) == 0 {
		s.renderInbox(w, r, "", "Those messages no longer exist.")
		return
	}

	// Bulk delete needs a confirmation (FR-6) and every spam action needs its
	// own confirmation (§10). The UI sets both after the user confirms; a
	// request that arrives without them is refused here.
	if action == "delete" {
		if r.FormValue("confirm") != "yes" {
			s.renderInbox(w, r, "", "Deleting needs confirmation. Select Delete again and confirm.")
			return
		}
		spam, err := s.spamCount(ctx, msgs)
		if err != nil {
			s.logger.Error("check spam before delete", "error", err)
		}
		if spam > 0 && r.FormValue("spam_confirm") != "yes" {
			s.renderInbox(w, r, "", fmt.Sprintf(
				"%d selected message(s) are classified Spam. Spam is never deleted automatically; confirm to move them to the Delete folder.",
				spam))
			return
		}
	}

	actor := sessionFrom(r).User
	if actor == "" {
		actor = "Sam"
	}

	var ok, failed int
	for _, m := range msgs {
		var err error
		switch action {
		case "delete", "save", "reply", "restore":
			folder := folderForAction(action)
			var label string
			label, err = s.actions.Move(ctx, m, folder)
			if err == nil {
				if serr := s.store.SetMessageLocation(ctx, m.ID, folder, label); serr != nil {
					s.logger.Error("record message location", "message_id", m.ID, "error", serr)
				}
				s.logMessageAction(ctx, m.ID, "move", actor,
					fmt.Sprintf("to=%s label=%q from=%q", folder, label, m.Mailbox))
			}
		case "mark_read", "mark_unread", "star", "unstar":
			mark := strings.TrimPrefix(action, "mark_")
			err = s.actions.Mark(ctx, m, mark)
			if err == nil {
				s.logMessageAction(ctx, m.ID, "mark", actor, "mark="+mark)
			}
		default:
			s.renderInbox(w, r, "", fmt.Sprintf("Unknown action %q.", action))
			return
		}
		if err != nil {
			failed++
			s.logger.Warn("triage action failed", "action", action, "message_id", m.ID, "error", err)
			continue
		}
		ok++
	}

	s.logAction(ctx, "bulk_"+action, actor,
		fmt.Sprintf("requested=%d ok=%d failed=%d ids=%s", len(msgs), ok, failed, joinIDs(ids)))

	note := actionSummary(action, ok, failed)
	if failed > 0 {
		note += " " + s.failureHint()
	}
	s.renderInbox(w, r, note, "")
}

// spamCount reports how many of the selected messages are classified Spam.
func (s *Server) spamCount(ctx context.Context, msgs []store.Message) (int, error) {
	ids := make([]int64, len(msgs))
	for i, m := range msgs {
		ids[i] = m.ID
	}
	classes, err := s.store.LatestClassifications(ctx, ids)
	if err != nil {
		return 0, err
	}
	n := 0
	for _, m := range msgs {
		if strings.EqualFold(strings.TrimSpace(classes[m.ID].Category), "Spam") {
			n++
		}
	}
	return n, nil
}

// folderForAction maps a bulk action to its destination app folder.
func folderForAction(action string) string {
	switch action {
	case "delete":
		return store.FolderDelete
	case "save":
		return store.FolderSaved
	case "reply":
		return store.FolderReplied
	default:
		return store.FolderInbox
	}
}

// actionSummary is the human note rendered above the refreshed list.
func actionSummary(action string, ok, failed int) string {
	verb := map[string]string{
		"delete":      "Moved %d message(s) to the Delete folder (recoverable).",
		"save":        "Saved %d message(s).",
		"reply":       "Marked %d message(s) as replied-to.",
		"restore":     "Restored %d message(s) to the inbox.",
		"mark_read":   "Marked %d message(s) read.",
		"mark_unread": "Marked %d message(s) unread.",
		"star":        "Starred %d message(s).",
		"unstar":      "Unstarred %d message(s).",
	}[action]
	if verb == "" {
		verb = "Updated %d message(s)."
	}
	msg := fmt.Sprintf(verb, ok)
	if failed > 0 {
		msg += fmt.Sprintf(" %d failed.", failed)
	}
	return msg
}

// failureHint explains the common reason a mailbox action fails.
func (s *Server) failureHint() string {
	return "Check GMAIL_USER, GMAIL_APP_PASSWORD, and the container log."
}

// logMessageAction records a per-message action; a logging failure must not fail
// the request.
func (s *Server) logMessageAction(ctx context.Context, messageID int64, action, actor, detail string) {
	if err := s.store.LogMessageAction(ctx, messageID, action, actor, detail); err != nil {
		s.logger.Warn("log message action", "message_id", messageID, "action", action, "error", err)
	}
}

// logAction records a summary action; a logging failure must not fail the
// request.
func (s *Server) logAction(ctx context.Context, action, actor, detail string) {
	if err := s.store.LogAction(ctx, action, actor, detail); err != nil {
		s.logger.Warn("log action", "action", action, "error", err)
	}
}

// parseIDList parses form values into unique, positive message ids.
func parseIDList(values []string) []int64 {
	seen := map[int64]struct{}{}
	var out []int64
	for _, v := range values {
		for _, part := range strings.Split(v, ",") {
			n, err := strconv.ParseInt(strings.TrimSpace(part), 10, 64)
			if err != nil || n <= 0 {
				continue
			}
			if _, dup := seen[n]; dup {
				continue
			}
			seen[n] = struct{}{}
			out = append(out, n)
		}
	}
	return out
}

// joinIDs renders ids for an action-log detail line.
func joinIDs(ids []int64) string {
	parts := make([]string, len(ids))
	for i, id := range ids {
		parts[i] = strconv.FormatInt(id, 10)
	}
	return strings.Join(parts, ",")
}

// folderLabel is the display name for an app folder.
func folderLabel(folder string) string {
	switch folder {
	case store.FolderDelete:
		return "Delete"
	case store.FolderSaved:
		return "Saved"
	case store.FolderReplied:
		return "Replied-to"
	case "all":
		return "All mail"
	default:
		return "Inbox"
	}
}

// Ensure the live client satisfies the interface at compile time.
var _ MailActions = (*mailops.Client)(nil)