package web

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"sort"
	"strings"

	"github.com/jackc/pgx/v5"

	"github.com/m/projax/internal/itemwrite"
	"github.com/m/projax/store"
)

// handleBulk renders the bulk-edit admin page: a filter bar (reusing the
// tree-page TreeFilter so URL params translate 1:1), a checkbox list of every
// matching item, and an action bar that posts to /admin/bulk/apply. The page
// is intentionally desktop-only — m bulk-edits from a keyboard.
func (s *Server) handleBulk(w http.ResponseWriter, r *http.Request) {
	items, err := s.Items.ListAll(r.Context())
	if err != nil {
		s.fail(w, r, err)
		return
	}
	linkKinds, err := s.linkKindsByItem(r.Context())
	if err != nil {
		s.fail(w, r, err)
		return
	}
	allTags, err := s.Items.AllTags(r.Context())
	if err != nil {
		s.fail(w, r, err)
		return
	}
	filter := ParseTreeFilter(r.URL.Query())
	// Bulk filters never default to status=active; the page is for editing,
	// and m wants to see done/archived rows too. Override the implicit default.
	if r.URL.Query().Get("status") == "" {
		filter.Status = nil
	}
	rows := filterFlat(items, filter, linkKinds)

	data := map[string]any{
		"Title":   "bulk edit",
		"Rows":    rows,
		"AllTags": allTags,
		"Filter":  filter,
		"Total":   len(items),
		"Matched": len(rows),
	}
	if r.Header.Get("HX-Request") == "true" {
		s.render(w, r, "bulk_section", data)
		return
	}
	s.render(w, r, "bulk", data)
}

// filterFlat returns every item matching the filter as a flat sorted list
// (no tree shape — bulk-edit treats items as a flat working set). Sort by
// primary path so siblings cluster together.
func filterFlat(items []*store.Item, f TreeFilter, linkKinds map[string]map[string]struct{}) []*store.Item {
	out := []*store.Item{}
	for _, it := range items {
		// Bulk filter is "match this item directly" — no descendant credit.
		// Override status default: if Status is nil treat as "any".
		if !bulkMatches(f, it, linkKinds[it.ID]) {
			continue
		}
		out = append(out, it)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].PrimaryPath() < out[j].PrimaryPath() })
	return out
}

// bulkMatches is a near-clone of TreeFilter.Matches but with Status treated
// as "any" when the slice is empty (the bulk-edit page deliberately surfaces
// every status when m has not picked one). Archived is still honoured
// through ShowArchived.
func bulkMatches(f TreeFilter, it *store.Item, itemLinkKinds map[string]struct{}) bool {
	if len(f.Status) > 0 && !contains(f.Status, it.Status) {
		return false
	}
	if it.Archived && !f.ShowArchived {
		// "any status" mode still hides archived rows unless ShowArchived is
		// explicit; otherwise a single archived item would dominate the list.
		// When the user filters to status=archived the previous branch already
		// accepted it, and ShowArchived stays default-off — which means we'd
		// still hide it here. Honour status=archived as an implicit ShowArchived.
		if !contains(f.Status, "archived") {
			return false
		}
	}
	for _, t := range f.Tags {
		if !it.HasTag(t) {
			return false
		}
	}
	if len(f.Management) > 0 {
		ok := false
		for _, m := range f.Management {
			if m == "unmanaged" && len(it.Management) == 0 {
				ok = true
				break
			}
			if it.HasManagement(m) {
				ok = true
				break
			}
		}
		if !ok {
			return false
		}
	}
	for _, h := range f.HasLinks {
		if _, ok := itemLinkKinds[h]; !ok {
			return false
		}
	}
	// Phase 5i Slice A: project scope. Same predicate as TreeFilter.Matches —
	// at least one of the item's paths must equal ProjectPath, with the
	// IncludeDescendants toggle gating the prefix-match for the subtree.
	// bulkMatches was a near-clone of Matches() that wasn't updated when
	// the project dim landed, so /admin/bulk silently ignored ?project=…
	// (and the chip's hidden-input round-trip too).
	if f.ProjectPath != "" {
		prefix := f.ProjectPath + "."
		hit := false
		for _, p := range it.Paths {
			if p == f.ProjectPath {
				hit = true
				break
			}
			if f.IncludeDescendants && strings.HasPrefix(p, prefix) {
				hit = true
				break
			}
		}
		if !hit {
			return false
		}
	}
	if f.Q != "" {
		q := strings.ToLower(f.Q)
		hit := strings.Contains(strings.ToLower(it.Title), q) ||
			strings.Contains(strings.ToLower(it.Slug), q) ||
			strings.Contains(strings.ToLower(it.ContentMD), q)
		if !hit {
			for _, p := range it.Paths {
				if strings.Contains(strings.ToLower(p), q) {
					hit = true
					break
				}
			}
		}
		if !hit {
			return false
		}
	}
	return true
}

// bulkAction parses the action descriptor sent by the form. Exactly one field
// is non-zero per request; the dispatch picks the matching code path.
type bulkAction struct {
	AddTag      string // free-text input
	RemoveTag   string
	SetMgmt     string // "mai" / "self" / "external" / "clear"
	SetStatus   string // "active" / "done" / "archived"
	SetPublic   string // "" / "make_public" / "make_private" — Phase 4d
	TimelineTodos string // "" / "exclude" / "include" — Phase 4f
}

func parseBulkAction(r *http.Request) bulkAction {
	get := func(k string) string { return strings.TrimSpace(r.FormValue(k)) }
	return bulkAction{
		AddTag:    strings.ToLower(get("add_tag")),
		RemoveTag: strings.ToLower(get("remove_tag")),
		SetMgmt:   get("set_mgmt"),
		SetStatus: get("set_status"),
		SetPublic: get("set_public"),
		TimelineTodos: get("timeline_todos"),
	}
}

func (a bulkAction) describe() string {
	switch {
	case a.AddTag != "":
		return "add tag " + a.AddTag
	case a.RemoveTag != "":
		return "remove tag " + a.RemoveTag
	case a.SetMgmt != "":
		return "set management " + a.SetMgmt
	case a.SetStatus != "":
		return "set status " + a.SetStatus
	case a.SetPublic == "make_public":
		return "make public"
	case a.SetPublic == "make_private":
		return "make private"
	case a.TimelineTodos == "exclude":
		return "exclude todos from timeline"
	case a.TimelineTodos == "include":
		return "re-include todos on timeline"
	}
	return ""
}

// handleBulkApply applies one action to every selected item in a single
// transaction. The form posts:
//   ids=<uuid>&ids=<uuid>&… plus one action field (add_tag / remove_tag /
//   set_mgmt / set_status). The action is validated here, dispatched to the
//   matching SQL, and returns the re-rendered list partial.
func (s *Server) handleBulkApply(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		s.fail(w, r, err)
		return
	}
	ids := dedupeStrings(r.Form["ids"])
	action := parseBulkAction(r)

	// Validation banners: re-render the section instead of replacing it with
	// a plain-text 400. The previous behaviour caused HTMX swaps to wipe out
	// the page chrome when m clicked Apply without ticking a row or filling
	// an action field. Two distinct messages so m can tell what he missed.
	var banner string
	switch {
	case len(ids) == 0 && action.describe() == "":
		banner = "Pick at least one row and choose an action before clicking Apply."
	case len(ids) == 0:
		banner = "No rows selected — tick the checkboxes for the rows you want to change."
	case action.describe() == "":
		banner = "No action chosen — type a tag, pick a management mode, or pick a status before clicking Apply."
	default:
		// Pre-flight bulk action via itemwrite where applicable. set_status
		// is the only bulk action today that mutates a validated field
		// (status enum); the others (add_tag / set_mgmt / set_public /
		// timeline_todos) operate outside the validator's rule set.
		if action.SetStatus != "" {
			if ve := itemwrite.ValidateFormat(itemwrite.Input{Title: "x", Slug: "x", Status: action.SetStatus}); ve != nil {
				banner = "Cannot apply: " + itemWriteBannerCopy(ve)
				break
			}
		}
		if err := s.applyBulk(r.Context(), ids, action); err != nil {
			s.fail(w, r, err)
			return
		}
	}

	// HTMX: re-render the list partial with the same filter context (and
	// banner, if any). The form sends every filter input alongside the
	// action via hx-include="#bulk-filter".
	if r.Header.Get("HX-Request") == "true" {
		s.renderBulkList(w, r, banner)
		return
	}
	// Non-HTMX fallback: redirect back to the bulk page preserving filters.
	dest := "/admin/bulk"
	if q := r.FormValue("filter_query"); q != "" {
		dest = "/admin/bulk?" + q
	}
	http.Redirect(w, r, dest, http.StatusSeeOther)
}

// applyBulk runs the action against every id in a single transaction so
// partial failures roll back. Each branch is its own UPDATE because Postgres
// array operators cannot be parameterised cleanly across different operations.
func (s *Server) applyBulk(ctx context.Context, ids []string, a bulkAction) error {
	tx, err := s.Store.Pool.BeginTx(ctx, pgx.TxOptions{})
	if err != nil {
		return fmt.Errorf("begin bulk tx: %w", err)
	}
	defer tx.Rollback(ctx)

	switch {
	case a.AddTag != "":
		// array_append guards against duplicate tag with a CASE: only append
		// when the tag isn't already present.
		_, err = tx.Exec(ctx, `
			update projax.items
			   set tags = case when $2 = any(tags) then tags else array_append(tags, $2) end
			 where id = any($1::uuid[]) and deleted_at is null`,
			ids, a.AddTag)
	case a.RemoveTag != "":
		_, err = tx.Exec(ctx, `
			update projax.items
			   set tags = array_remove(tags, $2)
			 where id = any($1::uuid[]) and deleted_at is null`,
			ids, a.RemoveTag)
	case a.SetMgmt != "":
		if a.SetMgmt == "clear" {
			_, err = tx.Exec(ctx, `
				update projax.items set management = '{}'::text[]
				 where id = any($1::uuid[]) and deleted_at is null`,
				ids)
		} else {
			// Replace management entirely — single-mode semantics matches
			// the chip group on detail.tmpl.
			_, err = tx.Exec(ctx, `
				update projax.items set management = ARRAY[$2]::text[]
				 where id = any($1::uuid[]) and deleted_at is null`,
				ids, a.SetMgmt)
		}
	case a.SetStatus != "":
		_, err = tx.Exec(ctx, `
			update projax.items set status = $2
			 where id = any($1::uuid[]) and deleted_at is null`,
			ids, a.SetStatus)
	case a.SetPublic == "make_public":
		_, err = tx.Exec(ctx, `
			update projax.items set public = true
			 where id = any($1::uuid[]) and deleted_at is null`,
			ids)
	case a.SetPublic == "make_private":
		_, err = tx.Exec(ctx, `
			update projax.items set public = false
			 where id = any($1::uuid[]) and deleted_at is null`,
			ids)
	case a.TimelineTodos == "exclude":
		// Idempotent: append 'todos' only when not already in the array.
		_, err = tx.Exec(ctx, `
			update projax.items
			   set timeline_exclude = case
			     when 'todos' = any(timeline_exclude) then timeline_exclude
			     else array_append(timeline_exclude, 'todos')
			   end
			 where id = any($1::uuid[]) and deleted_at is null`,
			ids)
	case a.TimelineTodos == "include":
		_, err = tx.Exec(ctx, `
			update projax.items
			   set timeline_exclude = array_remove(timeline_exclude, 'todos')
			 where id = any($1::uuid[]) and deleted_at is null`,
			ids)
	default:
		return errors.New("bulk: empty action")
	}
	if err != nil {
		return fmt.Errorf("bulk %s: %w", a.describe(), err)
	}
	return tx.Commit(ctx)
}

// normaliseFormStrings deduplicates, lowercases, and trims the slice of
// values a multi-value form key submitted. Mirrors what parseCSV would do
// to a single comma-joined string — but takes the already-split slice that
// r.Form[k] returns for multi-select inputs. Drops empties.
func normaliseFormStrings(in []string) []string {
	if len(in) == 0 {
		return []string{}
	}
	seen := map[string]struct{}{}
	out := make([]string, 0, len(in))
	for _, v := range in {
		t := strings.ToLower(strings.TrimSpace(v))
		if t == "" {
			continue
		}
		if _, ok := seen[t]; ok {
			continue
		}
		seen[t] = struct{}{}
		out = append(out, t)
	}
	return out
}

// renderBulkList re-renders the bulk section after a bulk apply or a
// validation failure. The apply form ships every filter input alongside the
// action via hx-include, so this reads them straight off r.Form (which the
// caller has already ParseForm'd). banner, when non-empty, surfaces an
// inline note above the action bar.
//
// Multi-value selects (tag, mgmt, status, has) submit ONE name=value pair
// per selected option. r.Form[k] is []string{...}; r.FormValue returns only
// the first. Must use the slice form here or the second+ values silently
// drop on every Apply round-trip.
func (s *Server) renderBulkList(w http.ResponseWriter, r *http.Request, banner string) {
	items, err := s.Items.ListAll(r.Context())
	if err != nil {
		s.fail(w, r, err)
		return
	}
	linkKinds, err := s.linkKindsByItem(r.Context())
	if err != nil {
		s.fail(w, r, err)
		return
	}
	allTags, err := s.Items.AllTags(r.Context())
	if err != nil {
		s.fail(w, r, err)
		return
	}
	filter := TreeFilter{
		Q:            strings.TrimSpace(r.FormValue("q")),
		Tags:         normaliseFormStrings(r.Form["tag"]),
		Management:   normaliseFormStrings(r.Form["mgmt"]),
		Status:       normaliseFormStrings(r.Form["status"]),
		HasLinks:     normaliseFormStrings(r.Form["has"]),
		ShowArchived: r.FormValue("show-archived") == "1",
	}
	rows := filterFlat(items, filter, linkKinds)
	s.render(w, r, "bulk_section", map[string]any{
		"Title":   "bulk edit",
		"Rows":    rows,
		"AllTags": allTags,
		"Filter":  filter,
		"Banner":  banner,
		"Total":   len(items),
		"Matched": len(rows),
	})
}

// handleBulkChip handles per-row inline chip edits — the small +/× buttons
// next to a tag chip on the bulk page. POST /admin/bulk/chip with id + op +
// kind + value. op ∈ {add, remove}; kind ∈ {tag, mgmt}. Returns the re-rendered
// chip cell.
func (s *Server) handleBulkChip(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		s.fail(w, r, err)
		return
	}
	id := strings.TrimSpace(r.FormValue("id"))
	op := strings.TrimSpace(r.FormValue("op"))
	kind := strings.TrimSpace(r.FormValue("kind"))
	val := strings.ToLower(strings.TrimSpace(r.FormValue("value")))
	if id == "" || op == "" || kind == "" || val == "" {
		http.Error(w, "id, op, kind, value all required", http.StatusBadRequest)
		return
	}
	a := bulkAction{}
	switch {
	case kind == "tag" && op == "add":
		a.AddTag = val
	case kind == "tag" && op == "remove":
		a.RemoveTag = val
	case kind == "mgmt" && op == "set":
		a.SetMgmt = val
	default:
		http.Error(w, "unsupported op/kind", http.StatusBadRequest)
		return
	}
	if err := s.applyBulk(r.Context(), []string{id}, a); err != nil {
		s.fail(w, r, err)
		return
	}
	it, err := s.Items.GetByID(r.Context(), id)
	if err != nil {
		s.fail(w, r, err)
		return
	}
	// Return just the chip cell's inner HTML (HTMX hx-swap=innerHTML on the <td>).
	// The chip templates render against the Item directly, not a map — we pass
	// it through .Item-keyed data so the same fragment-render path works.
	switch kind {
	case "tag":
		s.renderChip(w, "bulk_chip_tags", it)
	case "mgmt":
		s.renderChip(w, "bulk_chip_mgmt", it)
	default:
		http.Error(w, "unknown chip kind", http.StatusBadRequest)
	}
}

// renderChip renders a chip-cell template directly against an *Item.
func (s *Server) renderChip(w http.ResponseWriter, name string, it *store.Item) {
	t, ok := s.pages[name]
	if !ok {
		http.Error(w, "unknown page: "+name, http.StatusInternalServerError)
		return
	}
	entry := strings.ReplaceAll(name, "_", "-")
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := t.ExecuteTemplate(w, entry, it); err != nil {
		s.Logger.Error("render chip", "page", name, "err", err)
	}
}