package handlers

import (
	"database/sql"
	"github.com/andrew/go-computer/internal/db"
	"github.com/andrew/go-computer/internal/kanban"
	"net/http"
	"strings"
)

func HandleKanbanColumnsList(w http.ResponseWriter, r *http.Request) {
	v, e := kanban.GetColumns(r.Context(), database(r), user(r))
	respond(w, 200, v, e)
}
func columnData(b object) (object, error) {
	d := fields(b, "label color")
	if e := stringFields(d, "", "label color"); e != nil {
		return nil, e
	}
	if _, ok := d["label"]; ok {
		s := strings.TrimSpace(str(d, "label"))
		if s == "" {
			return nil, bad("Label required")
		}
		r := []rune(s)
		if len(r) > 40 {
			r = r[:40]
		}
		d["label"] = string(r)
	}
	return d, validColor(d)
}
func HandleKanbanColumnsCreate(w http.ResponseWriter, r *http.Request) {
	b, ok := read(w, r)
	if !ok {
		return
	}
	d, e := columnData(b)
	if e != nil {
		respond(w, 0, nil, e)
		return
	}
	if str(d, "label") == "" {
		respond(w, 0, nil, bad("Label required"))
		return
	}
	if _, ok := d["color"]; !ok {
		d["color"] = "#8b5cf6"
	}
	d["id"], d["userId"] = db.NewID(), user(r)
	var v object
	e = db.Transaction(r.Context(), database(r), func(tx *sql.Tx) error {
		if e := lockUser(r, tx); e != nil {
			return e
		}
		var n int
		if e := tx.QueryRowContext(r.Context(), `SELECT COALESCE(max(position),-1)+1 FROM "KanbanColumn" WHERE "userId"=$1`, user(r)).Scan(&n); e != nil {
			return e
		}
		d["position"] = n
		var e error
		v, e = db.Insert(r.Context(), tx, "KanbanColumn", d)
		return e
	})
	respond(w, 201, v, e)
}
func HandleKanbanColumnsReorder(w http.ResponseWriter, r *http.Request) {
	b, ok := read(w, r)
	if !ok {
		return
	}
	order, e := ids(b, "order")
	if e == nil {
		e = reorder(r, "KanbanColumn", "userId", order)
	}
	if e != nil {
		respond(w, 0, nil, e)
		return
	}
	HandleKanbanColumnsList(w, r)
}
func HandleKanbanColumnsUpdate(w http.ResponseWriter, r *http.Request) {
	b, ok := read(w, r)
	if !ok {
		return
	}
	d, e := columnData(b)
	if e != nil {
		respond(w, 0, nil, e)
		return
	}
	v, e := db.Update(r.Context(), database(r), "KanbanColumn", r.PathValue("id"), "userId", user(r), d)
	respond(w, 200, v, e)
}

// HandleKanbanCardsMove moves or reorders one card on the board. It carries
// the same optimistic-concurrency version as a bookmark PUT (review CR-04):
// a card edited or moved elsewhere is a 409, and the board reloads instead of
// silently clobbering it. The target column's positions are normalized in the
// same transaction, so dragging inside a column survives reloads.
func HandleKanbanCardsMove(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	b, ok := read(w, r)
	if !ok {
		return
	}
	columnID := strings.TrimSpace(str(b, "columnId"))
	if columnID == "" {
		respond(w, 0, nil, bad("columnId is required"))
		return
	}
	rawPosition, hasPosition := b["position"]
	if !hasPosition {
		respond(w, 0, nil, bad("position is required"))
		return
	}
	f, ok := rawPosition.(float64)
	if !ok || f < 0 || f != float64(int64(f)) {
		respond(w, 0, nil, bad("position must be a non-negative integer"))
		return
	}
	position := int(f)
	baseVersion, hasVersion := 0, false
	if v, present := b["version"]; present {
		f, isNum := v.(float64)
		if !isNum || f < 0 || f != float64(int64(f)) {
			respond(w, 0, nil, bad("version must be a non-negative integer"))
			return
		}
		baseVersion, hasVersion = int(f), true
	}
	if !hasVersion {
		respond(w, 0, nil, bad("version is required when moving a card; refetch it and retry"))
		return
	}
	// Ensure the default board exists before the transaction reads columns.
	if _, e := kanban.GetColumns(r.Context(), database(r), user(r)); e != nil {
		respond(w, 0, nil, e)
		return
	}
	e := db.Transaction(r.Context(), database(r), func(tx *sql.Tx) error {
		if e := lockUser(r, tx); e != nil {
			return e
		}
		cur, e := owned(r, tx, "Bookmark", id, "ownerId")
		if e != nil {
			return e
		}
		if stored, _ := cur["version"].(float64); int(stored) != baseVersion {
			return conflict("Bookmark was modified elsewhere; reload to see the latest version")
		}
		if _, e := owned(r, tx, "KanbanColumn", columnID, "userId"); e != nil {
			return bad("Invalid columnId")
		}
		cols, e := db.Many(r.Context(), tx, `SELECT to_jsonb(c) FROM "KanbanColumn" c WHERE "userId"=$1 ORDER BY position,id`, user(r))
		if e != nil {
			return e
		}
		// Resolve legacy cards (kanbanStatus only) the same way the board does,
		// then normalize every card in the target column to explicit
		// membership plus a contiguous position. That makes the new order
		// durable without requiring a schema backfill.
		rows, e := db.Many(r.Context(), tx, `SELECT jsonb_build_object('id',b.id,'kanbanColumnId',b."kanbanColumnId",'kanbanStatus',b."kanbanStatus") FROM "Bookmark" b WHERE b."ownerId"=$1 ORDER BY b."kanbanPosition",b."updatedAt" DESC,b.id DESC`, user(r))
		if e != nil {
			return e
		}
		target := make([]string, 0, len(rows))
		for _, row := range rows {
			if str(row, "id") == id {
				continue
			}
			if kanban.ResolveColumnID(row, cols) == columnID {
				target = append(target, str(row, "id"))
			}
		}
		if position > len(target) {
			position = len(target)
		}
		target = append(target, "")
		copy(target[position+1:], target[position:])
		target[position] = id
		if _, e := tx.ExecContext(r.Context(), `UPDATE "Bookmark" AS b SET "kanbanColumnId"=$1,"kanbanPosition"=t.ord-1 FROM unnest($2::text[]) WITH ORDINALITY AS t(bid,ord) WHERE b.id=t.bid AND b."ownerId"=$3`, columnID, target, user(r)); e != nil {
			return e
		}
		// Only the moved card's revision advances; reindexing its neighbours is
		// board placement, not a content edit.
		if _, e := tx.ExecContext(r.Context(), `UPDATE "Bookmark" SET version=version+1,"updatedAt"=now() WHERE id=$1 AND "ownerId"=$2`, id, user(r)); e != nil {
			return e
		}
		return nil
	})
	if e != nil {
		respond(w, 0, nil, e)
		return
	}
	v, e := bookmark(r, id, false)
	respond(w, 200, v, e)
}

func HandleKanbanColumnsDelete(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	var dest string
	var moved int
	e := db.Transaction(r.Context(), database(r), func(tx *sql.Tx) error {
		// The user row is the single serialization point for board mutations
		// (review CR-05): bookmark create/update take the same lock before
		// validating/assigning kanbanColumnId, so this handler's snapshot of
		// affected bookmarks, the move and the column delete cannot interleave
		// with a competing assignment.
		if e := lockUser(r, tx); e != nil {
			return e
		}
		cols, e := db.Many(r.Context(), tx, `SELECT to_jsonb(c) FROM "KanbanColumn" c WHERE "userId"=$1 ORDER BY position,id`, user(r))
		if e != nil {
			return e
		}
		found := false
		remaining := []object{}
		for _, c := range cols {
			if str(c, "id") == id {
				found = true
			} else {
				remaining = append(remaining, c)
			}
		}
		if !found {
			return db.ErrNotFound
		}
		if len(remaining) == 0 {
			return bad("A board needs at least one column")
		}
		dest = str(remaining[0], "id")
		// Only the three columns ResolveColumnID needs, and one set-based
		// UPDATE for the whole move instead of a round trip per bookmark.
		bms, e := db.Many(r.Context(), tx, `SELECT jsonb_build_object('id',b.id,'kanbanColumnId',b."kanbanColumnId",'kanbanStatus',b."kanbanStatus") FROM "Bookmark" b WHERE "ownerId"=$1`, user(r))
		if e != nil {
			return e
		}
		moveIDs := make([]string, 0, len(bms))
		for _, b := range bms {
			if kanban.ResolveColumnID(b, cols) == id {
				moveIDs = append(moveIDs, str(b, "id"))
			}
		}
		if len(moveIDs) > 0 {
			// The move is a mutation covered by the bookmark concurrency
			// contract (review CR-04): bumping version turns any client
			// snapshot that still shows the old column into a 409 on its
			// next save instead of letting it silently move the bookmark
			// back.
			if _, e := tx.ExecContext(r.Context(), `UPDATE "Bookmark" SET "kanbanColumnId"=$1,version=version+1,"updatedAt"=now() WHERE id=ANY($2::text[])`, dest, moveIDs); e != nil {
				return e
			}
			moved = len(moveIDs)
		}
		if _, e := tx.ExecContext(r.Context(), `DELETE FROM "KanbanColumn" WHERE id=$1 AND "userId"=$2`, id, user(r)); e != nil {
			return e
		}
		order := make([]string, len(remaining))
		for i, c := range remaining {
			order[i] = str(c, "id")
		}
		if _, e := tx.ExecContext(r.Context(), `UPDATE "KanbanColumn" AS k SET position=t.ord-1 FROM unnest($1::text[]) WITH ORDINALITY AS t(cid,ord) WHERE k.id=t.cid`, order); e != nil {
			return e
		}
		return nil
	})
	respond(w, 200, object{"ok": true, "movedTo": dest, "moved": moved}, e)
}