import type { ClassSchema, SchemaFingerprint } from '../../types/auto-group'

export function serializeFingerprint(schemas: ClassSchema[]): SchemaFingerprint {
  return {
    version: 1,
    classes: schemas.map(s => ({
      kind: s.classKind,
      subKind: s.subKind,
      tokenLength: s.tokenLength,
      columns: s.columns.map(c => ({
        name: c.displayName ?? c.name,
        role: c.role ?? 'factor',
        sourceIndices: c.sourceIndices,
        binning: c.binning,
        ops: c.ops,
      })),
      groupBy: s.groupBy,
    })),
  }
}

export function restoreFingerprint(
  fp: SchemaFingerprint,
  current: ClassSchema[],
): ClassSchema[] {
  return fp.classes.map(snap => {
    // Match on token length too when the snapshot carries one, so length-split
    // classes sharing a (kind, subKind) restore to the right schema. Snapshots
    // saved before token-length splitting have no `tokenLength`; for those we
    // match on (kind, subKind) and prefer the candidate with the same column
    // count, so an old single-class fingerprint lands on the compatible split
    // instead of throwing on the first (wrong-arity) hit.
    const candidates = current.filter(
      c =>
        c.classKind === snap.kind &&
        c.subKind === snap.subKind &&
        (snap.tokenLength == null || c.tokenLength == null || c.tokenLength === snap.tokenLength),
    )
    const target =
      candidates.find(c => c.columns.length === snap.columns.length) ?? candidates[0]
    if (!target) {
      throw new Error(
        `Fingerprint class not present in current input: ${snap.kind}${snap.subKind ? '/' + snap.subKind : ''}`,
      )
    }
    if (target.columns.length !== snap.columns.length) {
      throw new Error(
        `Saved schema expects ${snap.columns.length} columns, current data has ${target.columns.length} for class ${snap.kind}${snap.subKind ? '/' + snap.subKind : ''}. column count mismatch`,
      )
    }
    return {
      ...target,
      groupBy: snap.groupBy,
      columns: target.columns.map((col, i) => ({
        ...col,
        displayName: snap.columns[i].name,
        role: snap.columns[i].role,
        binning: snap.columns[i].binning,
        ops: snap.columns[i].ops,
      })),
    }
  })
}