import type { ColumnDef } from "../components/data-table/types"

export type ColumnPinPolicy = {
  defaults: Record<string, "left" | "right">
  lockedLeft: string[]
  lockedRight: string[]
}

/** Derive default / locked pin policy from hub `ColumnDef[]`. */
export function columnPinPolicyFromDefs<T extends Record<string, unknown>>(
  columns: ColumnDef<T>[],
): ColumnPinPolicy {
  const defaults: Record<string, "left" | "right"> = {}
  const lockedLeft: string[] = []
  const lockedRight: string[] = []

  for (const col of columns) {
    if (col.defaultPin) defaults[col.key] = col.defaultPin
    if (col.lockPin && col.defaultPin === "left") lockedLeft.push(col.key)
    if (col.lockPin && col.defaultPin === "right") lockedRight.push(col.key)
  }

  return { defaults, lockedLeft, lockedRight }
}

/**
 * Merge persisted pins with column defaults. Saved user pins win for
 * non-locked columns; locked columns always match `ColumnDef.lockPin`.
 * Default pins apply only when a column has no saved pin entry yet.
 */
export function reconcileColumnPins(
  saved: Record<string, "left" | "right">,
  policy: ColumnPinPolicy,
): Record<string, "left" | "right"> {
  const next = { ...saved }
  for (const [key, pin] of Object.entries(policy.defaults)) {
    if (!(key in next)) next[key] = pin
  }
  for (const key of policy.lockedLeft) next[key] = "left"
  for (const key of policy.lockedRight) next[key] = "right"
  return next
}

/** Keep locked edge columns anchored; preserve middle order from saved state. */
export function mergeColOrderWithPinPolicy(
  saved: string[],
  columnKeys: Set<string>,
  policy?: ColumnPinPolicy,
): string[] {
  const lockedLeft = policy?.lockedLeft.filter(k => columnKeys.has(k)) ?? []
  const lockedRight = policy?.lockedRight.filter(k => columnKeys.has(k)) ?? []
  const locked = new Set([...lockedLeft, ...lockedRight])
  const middle = saved.filter(k => columnKeys.has(k) && !locked.has(k))
  const inMiddle = new Set(middle)

  for (const key of columnKeys) {
    if (locked.has(key) || inMiddle.has(key)) continue
    middle.push(key)
    inMiddle.add(key)
  }

  return [...lockedLeft, ...middle, ...lockedRight]
}