import { choiceOptions, isDerivedLink, isMachineWritten, ratingMax } from "./types";
import type { Field } from "./types";

function choiceMatch(raw: string, allowed: string[]): string | undefined {
  const wanted = raw.trim().toLowerCase();
  return allowed.find((value) => value.trim().toLowerCase() === wanted);
}

function numericValue(raw: string): string | undefined {
  const clean = raw.trim().replace(/[$,%\s]/g, "");
  if (clean === "") return "";
  const value = Number(clean);
  return Number.isFinite(value) ? String(value) : undefined;
}

/**
 * Convert one clipboard cell into the overlay store's string contract. `undefined` means the
 * paste is invalid and the caller must reject the whole operation; an empty string is a valid
 * clear. Choice fields always return their canonical declared spelling.
 */
export function coerceClipboardValue(
  field: Field,
  raw: string,
  allowedChoices: string[] = choiceOptions(field)
): string | undefined {
  // ⭐ OWNER ITEM 4 (2026-08-06) — THE PASTE DOOR, which the type switch below structurally
  // cannot cover. This module's own design note is that a paste never opens an editor, so a cell
  // that is read-only by NATURE and absent from the switch is uneditable by keyboard and
  // overwritable by Ctrl+V. Every case below is a TYPE; `isMachineWritten` is not type-based — an
  // automation-filled column is an ordinary `text` field wearing a tag — so the Instagram preset
  // columns fell straight through it. `grid_events` refuses the write either way, but a
  // multi-cell paste would paint optimistically across them and then bounce, which reads to the
  // person doing it as the app losing their data rather than as a wall.
  if (isMachineWritten(field)) return undefined;
  // ⭐ 2026-08-07 — the DERIVED half of `link`, refused for the same reason and by the same
  // shape: it is read-only per FIELD, not per type, so the switch below structurally cannot see
  // it. The server rewrites the cell on the next refresh pass, so a pasted value would paint,
  // survive a moment, and vanish — the failure this whole function exists to prevent.
  if (isDerivedLink(field)) return undefined;
  const value = raw.replace(/\r/g, "");
  const trimmed = value.trim();
  switch (field.type) {
    case "formula":
    case "created_time":
    case "status":
    // ⭐ 2026-08-07 — a ROLLUP cell is an aggregate the host computed. Same argument as
    // `automation` below: a paste would be overwritten by the next refresh with nothing on any
    // surface saying so.
    case "rollup":
    // C5-AUTOFIELD (wave 18) — an automation cell is what the last RUN wrote, so a paste into
    // one is refused HERE and not only by the renderer. `READONLY_CELL_TYPES` decides what
    // gets an editor; a paste never opens one, so a type that is read-only by nature and
    // absent from this list would be uneditable by keyboard and overwritable by Ctrl+V —
    // and the next run would silently replace whatever landed.
    case "automation":
      return undefined;
    case "checkbox": {
      if (trimmed === "") return "";
      const key = trimmed.toLowerCase();
      if (["1", "true", "yes", "y", "on", "checked", "x"].includes(key)) return "1";
      if (["0", "false", "no", "n", "off", "unchecked"].includes(key)) return "";
      return undefined;
    }
    case "int":
    case "currency":
    case "pct":
      return numericValue(value);
    case "rating": {
      if (trimmed === "") return "";
      const n = Number(trimmed);
      return Number.isInteger(n) && n >= 1 && n <= ratingMax(field)
        ? String(n)
        : undefined;
    }
    case "select":
    case "user":
      return trimmed === "" ? "" : choiceMatch(trimmed, allowedChoices);
    case "multiselect": {
      if (trimmed === "") return "";
      const out: string[] = [];
      const seen = new Set<string>();
      for (const part of value.split(/[,\n]/)) {
        if (!part.trim()) continue;
        const match = choiceMatch(part, allowedChoices);
        if (!match) return undefined;
        const key = match.toLowerCase();
        if (!seen.has(key)) {
          seen.add(key);
          out.push(match);
        }
      }
      return out.length ? out.join(",") : "";
    }
    /**
     * ⭐ WAVE-26 ITEM 3 — a pasted date is NORMALISED to the stored contract, not stored as
     * whatever text happened to parse.
     *
     * It used to `return trimmed` for anything `Date.parse` accepted, which meant pasting a
     * DISPLAY string put a display string in the cell: `8/5/2026` from Excel, or — after item 3
     * changed the rendering — `Aug 5, 2026` copied out of this very grid. The cell then LOOKED
     * right (an unparseable date renders verbatim) while the stored value had stopped being a
     * date: it sorts as text, no date filter matches it, and the JSON export carries the browser
     * locale's spelling of somebody's calendar.
     *
     * ⚠ AN ALREADY-CANONICAL VALUE IS LEFT ALONE, and that guard is the load-bearing half.
     * `new Date("2026-08-05")` is UTC midnight, so re-deriving `YYYY-MM-DD` from its LOCAL parts
     * would move it to the 4th for every viewer west of Greenwich — a normaliser that corrupts
     * exactly the values that needed no normalising. Anything already starting with an ISO day
     * (bare, or carrying a time) passes through untouched.
     *
     * A display string, by contrast, was written in the reader's own clock, so its LOCAL parts
     * are the day they meant — never `toISOString()`, which would shift it back the other way.
     */
    case "date": {
      if (trimmed === "") return "";
      if (/^\d{4}-\d{2}-\d{2}/.test(trimmed)) return trimmed;
      const parsed = new Date(trimmed);
      if (Number.isNaN(parsed.getTime())) return undefined;
      const pad = (n: number) => String(n).padStart(2, "0");
      return `${parsed.getFullYear()}-${pad(parsed.getMonth() + 1)}-${pad(parsed.getDate())}`;
    }
    default:
      return value;
  }
}

/** The product deliberately supports vertical field paste, never a cross-field matrix. */
export function isSingleColumnClipboard(values: readonly (readonly string[])[]): boolean {
  return values.length > 0 && values.every((row) => row.length === 1);
}

export interface GridCopyProvenance {
  fieldKey: string | null;
  /** The native copy event follows the grid key event; this short arm identifies that one event. */
  armedUntil: number;
}

export const EMPTY_GRID_COPY_PROVENANCE: GridCopyProvenance = {
  fieldKey: null,
  armedUntil: 0,
};

export function markGridCopy(
  fieldKey: string | null,
  now: number
): GridCopyProvenance {
  return { fieldKey, armedUntil: now + 1_000 };
}

/**
 * Preserve provenance for the native copy event belonging to the grid shortcut. Any later
 * document copy is external to the grid and clears it, so stale source metadata cannot block
 * an unrelated paste.
 */
export function observeCopyEvent(
  provenance: GridCopyProvenance,
  now: number
): GridCopyProvenance {
  return now <= provenance.armedUntil
    ? { ...provenance, armedUntil: 0 }
    : EMPTY_GRID_COPY_PROVENANCE;
}

export interface FieldPastePatch {
  pid: number;
  value: string;
}

/**
 * The selected RECTANGLE, in glide's own coordinates (`GridSelection.current.range`).
 * `width`/`height` are counts of columns/rows, so a single clicked cell is 1×1.
 */
export interface PasteSelection {
  x: number;
  y: number;
  width: number;
  height: number;
}

/**
 * Wave-15 item 3 (R8) — HOW MANY ROWS a paste writes.
 *
 * The defect this replaces: the target rows were walked down from the anchor for exactly
 * `values.length` rows and THE SELECTION WAS NEVER CONSULTED. So copying one cell, selecting
 * fifty rows and pasting wrote ONE — the fifty-row selection was painted, obeyed by nothing, and
 * the user had no way to tell the difference between "it filled" and "it filled the first row"
 * without scrolling.
 *
 * R8: the clipboard TILES TO FILL the selection. A pattern of K repeats top-to-bottom until N
 * rows are covered (`planFieldPaste` takes `values[i % K]`), and N need not be a multiple of K —
 * Excel refuses that, Airtable tiles, and the owner asked for tiling. A clipboard LARGER than
 * the selection is not truncated either: it pastes from the anchor downward, past the selection
 * end, because the rows the user copied are the thing they chose and silently dropping the tail
 * would be the same class of quiet lie as the bug above.
 *
 * ⚠ `target` IS the selection origin whenever there is a selection — glide's `onPasteInternal`
 * computes `target = [current.range.x, current.range.y]` (data-editor.tsx:3361), MEASURED, not
 * assumed. The equality guards below are therefore normally trivially true; they earn their
 * place by covering glide's OTHER two target branches (a whole-column or whole-row selection
 * with no `current`), where `range` is undefined and the honest answer is today's behaviour.
 */
export function pasteRowCount(
  clipboardRows: number,
  selection: PasteSelection | undefined,
  target: { col: number; row: number }
): number {
  if (clipboardRows <= 0) return 0;
  // No rectangle to fill: paste the clipboard as it comes, from the anchor down.
  if (!selection) return clipboardRows;
  // Same-field VERTICAL paste only, exactly as today (`isSingleColumnClipboard` is the other
  // half). A selection spanning columns describes a matrix this product deliberately refuses,
  // so filling it would invent a policy nobody asked for.
  if (selection.width !== 1) return clipboardRows;
  // The paste has to be landing IN the selection for the selection to mean anything.
  if (selection.x !== target.col || selection.y !== target.row) return clipboardRows;
  return Math.max(clipboardRows, selection.height);
}

/**
 * The whole paste policy as a pure, atomic plan. CustomerGrid supplies the actual target row
 * pids (null for a group/header row) — `pasteRowCount` of them — then applies the returned
 * patches only when every value passed. `null` means apply nothing.
 *
 * ⚠ ONE PATCH PER TARGET ROW, not per clipboard row (wave-15 R8). The clipboard is a PATTERN
 * that repeats: row i takes `values[i % values.length]`. With one copied cell and fifty targets
 * that is fifty identical patches; with a two-row pattern and seven targets it is
 * A B A B A B A.
 */
export function planFieldPaste({
  field,
  sourceFieldKey,
  editable,
  values,
  targetPids,
  allowedChoices,
}: {
  field: Field;
  sourceFieldKey: string | null;
  editable: boolean;
  values: readonly (readonly string[])[];
  targetPids: readonly (number | null)[];
  allowedChoices?: string[];
}): FieldPastePatch[] | null {
  if (!editable || !isSingleColumnClipboard(values)) return null;
  if (sourceFieldKey && sourceFieldKey !== field.key) return null;
  // ⚠ This was `!==` until wave 15, and the change is deliberate rather than a loosening.
  // FEWER targets than clipboard rows still refuses — that would drop copied rows on the floor
  // silently. MORE is now legal, because that IS the tile-to-fill case. The null test is
  // untouched and is what keeps the whole operation ATOMIC: a selection running past the last
  // record, or over a group header, refuses everything rather than half-writing.
  if (targetPids.length < values.length || targetPids.some((pid) => pid == null))
    return null;
  const patches: FieldPastePatch[] = [];
  for (let index = 0; index < targetPids.length; index += 1) {
    const value = coerceClipboardValue(
      field, values[index % values.length][0], allowedChoices);
    const pid = targetPids[index];
    if (value === undefined || pid == null) return null;
    patches.push({ pid, value });
  }
  return patches;
}