import type { ExamTemplateDetail, TemplateReplacePayload } from '../../types/exam.types'

export const PAGE_HEIGHT = 1100
export const PAGE_WIDTH = 780

export type ExamCanvasRegionKind = 'response' | 'context' | 'question_number' | 'mark_area' | 'reference' | 'furniture'
export type ExamCanvasShapeKind = 'boundary' | 'part' | ExamCanvasRegionKind

export interface CanvasBounds { x: number; y: number; w: number; h: number }

export interface ExamCanvasShapeModel {
  /** Stable domain UUID persisted to Supabase. Do not reuse tldraw shape ids for new shapes. */
  id: string
  kind: ExamCanvasShapeKind
  x: number
  y: number
  w: number
  h: number
  label?: string
  maxMarks?: number
  answerType?: 'written' | 'mcq' | 'short' | 'diagram'
  responseForm?: 'lines' | 'answer-box' | 'working' | 'diagram' | 'tick-boxes' | 'table' | 'blanks'
  contextType?: string
  questionId?: string | null
}

export function pageForY(y: number): number {
  return Math.max(1, Math.floor(y / PAGE_HEIGHT) + 1)
}

export function isUuid(value: string | null | undefined): value is string {
  return typeof value === 'string' && /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i.test(value)
}

export function newDomainId(): string {
  if (typeof crypto !== 'undefined' && 'randomUUID' in crypto) {
    return crypto.randomUUID()
  }
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, (c) => {
    const r = Math.floor(Math.random() * 16)
    const v = c === 'x' ? r : (r % 4) + 8
    return v.toString(16)
  })
}

function bounds(shape: Pick<ExamCanvasShapeModel, 'x' | 'y' | 'w' | 'h'>): CanvasBounds {
  return { x: shape.x, y: shape.y, w: shape.w, h: shape.h }
}

function contains(outer: CanvasBounds, inner: CanvasBounds): boolean {
  const ox2 = outer.x + outer.w
  const oy2 = outer.y + outer.h
  const ix2 = inner.x + inner.w
  const iy2 = inner.y + inner.h
  return inner.x >= outer.x && inner.y >= outer.y && ix2 <= ox2 && iy2 <= oy2
}

function bandContains(top: ExamCanvasShapeModel, bottom: ExamCanvasShapeModel, shape: ExamCanvasShapeModel): boolean {
  const minY = Math.min(top.y, bottom.y)
  const maxY = Math.max(top.y, bottom.y)
  const cy = shape.y + shape.h / 2
  return cy >= minY && cy <= maxY
}

export function serializeCanvasShapes(template: ExamTemplateDetail, shapes: ExamCanvasShapeModel[]): TemplateReplacePayload {
  const orderedBoundaries = shapes
    .filter((s) => s.kind === 'boundary')
    .sort((a, b) => (pageForY(a.y) - pageForY(b.y)) || (a.y - b.y))
  const parts = shapes.filter((s) => s.kind === 'part')
  const regions = shapes.filter((s) => s.kind !== 'boundary' && s.kind !== 'part')

  const questions: TemplateReplacePayload['questions'] = []
  const boundaries: TemplateReplacePayload['boundaries'] = []
  const bands: Array<{ questionId: string; top: ExamCanvasShapeModel; bottom: ExamCanvasShapeModel }> = []

  for (let i = 0; i < orderedBoundaries.length; i += 2) {
    const top = orderedBoundaries[i]
    const bottom = orderedBoundaries[i + 1]
    if (!top || !bottom) break
    const qNum = bands.length + 1
    const questionId = isUuid(top.questionId) ? top.questionId : isUuid(bottom.questionId) ? bottom.questionId : newDomainId()
    const label = top.label?.replace(/\s+(start|end)$/i, '') || bottom.label?.replace(/\s+(start|end)$/i, '') || `Q${qNum}`
    questions.push({ id: questionId, label, order: qNum - 1, max_marks: 0, is_container: true, mark_scheme: {} })
    bands.push({ questionId, top, bottom })
    for (const b of [top, bottom]) {
      boundaries.push({ id: isUuid(b.id) ? b.id : newDomainId(), question_id: questionId, label: b === top ? `${label} start` : `${label} end`, page_index: pageForY(b.y) - 1, y: b.y, bounds: bounds(b), source: 'manual', confirmed: true })
    }
  }

  const partQuestionIds = new Map<string, string>()
  parts.sort((a, b) => (a.y - b.y) || (a.x - b.x)).forEach((part, index) => {
    const parentBand = bands.find((band) => bandContains(band.top, band.bottom, part))
    const qid = isUuid(part.questionId) ? part.questionId : isUuid(part.id) ? part.id : newDomainId()
    partQuestionIds.set(part.id, qid)
    questions.push({ id: qid, parent_id: parentBand?.questionId ?? null, label: part.label || `Part ${index + 1}`, order: index, max_marks: Number(part.maxMarks ?? 0), answer_type: part.answerType ?? 'written', mcq_options: null, mark_scheme: {}, is_container: false, spec_ref: null, bounds: bounds(part), page: pageForY(part.y) })
  })

  const response_areas: TemplateReplacePayload['response_areas'] = []
  for (const region of regions) {
    const containingPart = parts.find((part) => contains(bounds(part), bounds(region)))
    const fallbackPart = parts.find((part) => pageForY(part.y) === pageForY(region.y)) ?? parts[0]
    const questionId = containingPart ? partQuestionIds.get(containingPart.id) : fallbackPart ? partQuestionIds.get(fallbackPart.id) : undefined
    if (!questionId) continue
    const kind = region.kind as ExamCanvasRegionKind
    response_areas.push({ id: isUuid(region.id) ? region.id : newDomainId(), question_id: questionId, page: pageForY(region.y), bounds: bounds(region), kind, response_form: kind === 'response' ? (region.responseForm ?? 'lines') : null, context_type: kind === 'context' ? (region.contextType ?? 'generic') : null, source: 'manual', confirmed: true, confidence: null })
  }

  return { meta: { title: template.title, subject: template.subject ?? undefined, page_count: template.page_count ?? undefined, status: template.status }, questions, response_areas, boundaries }
}

export function shapesFromTemplate(detail: ExamTemplateDetail): ExamCanvasShapeModel[] {
  const shapes: ExamCanvasShapeModel[] = []
  const questions = new Map(detail.questions.map((q) => [q.id, q]))
  for (const b of detail.boundaries ?? []) {
    const bb = b.bounds ?? { x: 48, y: b.y, w: PAGE_WIDTH - 96, h: 8 }
    shapes.push({ id: b.id, kind: 'boundary', x: Number(bb.x ?? 48), y: Number(bb.y ?? b.y), w: Number(bb.w ?? PAGE_WIDTH - 96), h: Number(bb.h ?? 8), label: b.label ?? undefined, questionId: b.question_id })
  }
  for (const q of detail.questions ?? []) {
    if (q.is_container || !q.bounds) continue
    shapes.push({ id: q.id, kind: 'part', x: Number(q.bounds.x ?? 80), y: Number(q.bounds.y ?? 120), w: Number(q.bounds.w ?? 420), h: Number(q.bounds.h ?? 180), label: q.label, maxMarks: q.max_marks, answerType: q.answer_type ?? 'written', questionId: q.id })
  }
  for (const r of detail.response_areas ?? []) {
    const bb = r.bounds ?? { x: 100, y: (r.page - 1) * PAGE_HEIGHT + 360, w: 360, h: 120 }
    const q = questions.get(r.question_id)
    shapes.push({ id: r.id, kind: r.kind, x: Number(bb.x ?? 100), y: Number(bb.y ?? (r.page - 1) * PAGE_HEIGHT + 360), w: Number(bb.w ?? 360), h: Number(bb.h ?? 120), label: q ? `→ ${q.label}` : r.kind, responseForm: r.response_form ?? undefined, contextType: r.context_type ?? undefined, questionId: r.question_id })
  }
  return shapes
}