/**
 * Meal API — the whole backend in one file.
 *
 * - Domain: a **Meal** is one item on the menu. The collection lives at /api/menu.
 * - Validation: zod v4 schemas are the single source of truth. Elysia consumes them
 *   directly (Standard Schema), so the same schema validates the request, types the
 *   handler and documents the endpoint in the OpenAPI spec at /openapi.
 * - Runs on Node (`node server.js`) and Bun (`bun server.js`) from this same file.
 */
import { Elysia, status } from 'elysia'
import { node } from '@elysiajs/node'
import { openapi } from '@elysiajs/openapi'
import { readFileSync } from 'node:fs'
import { fileURLToPath } from 'node:url'
import { z } from 'zod'

const PORT = process.env.PORT || 3000

// ---------------------------------------------------------------------------
// Schemas
// ---------------------------------------------------------------------------

/** The categories a meal can belong to. */
const MEAL_CATEGORIES = ['appetizer', 'main', 'dessert', 'drink']

const ID_MESSAGE = 'ID must be a whole number, like 1.'

/** `:id` path param. Coerces "2" to 2 and rejects "abc", "0", "-1" and "1.5". */
const mealIdSchema = z.coerce.number({ error: ID_MESSAGE }).int(ID_MESSAGE).min(1, ID_MESSAGE)

/** What a client sends to create (or fully replace) a meal. */
const mealDraftSchema = z.object({
  name: z
    .string()
    .trim()
    .min(1, 'Name is required.')
    .max(80, 'Keep the name under 80 characters.'),
  category: z.enum(MEAL_CATEGORIES, {
    error: `Pick a category: ${MEAL_CATEGORIES.join(', ')}.`,
  }),
  // Strict number on purpose: an empty form field arrives as "" and must be
  // rejected as missing, never quietly coerced into a ₱0 meal.
  price: z
    .number({ error: 'Price is required.' })
    .nonnegative('Price cannot be negative.')
    .max(100000, 'That price looks too high.')
    .refine(
      (value) => Math.round(value * 100) / 100 === value,
      'Price can have at most 2 decimal places.',
    ),
  description: z.string().trim().max(240, 'Keep the description under 240 characters.').optional(),
  available: z.boolean({ error: 'Available must be true or false.' }).optional(),
})

/** What the API stores and returns: the draft, plus the server-managed fields. */
const mealSchema = mealDraftSchema.required({ description: true, available: true }).extend({
  id: z.number().int().min(1),
  createdAt: z.iso.datetime(),
  updatedAt: z.iso.datetime(),
})

/** PATCH body — every field optional, but an empty patch is rejected. */
const mealPatchSchema = mealDraftSchema
  .partial()
  .refine((patch) => Object.keys(patch).length > 0, 'Provide at least one field to update.')

/** Filtering / sorting for the list endpoint. */
const mealQuerySchema = z.object({
  category: z.enum(MEAL_CATEGORIES, {
    error: `Unknown category. Pick one of: ${MEAL_CATEGORIES.join(', ')}.`,
  }).optional(),
  available: z.stringbool({ error: 'available must be true or false.' }).optional(),
  search: z.string().trim().min(1, 'Search cannot be empty.').optional(),
  sort: z.enum(['name', 'price', 'createdAt'], { error: 'Sort by name, price or createdAt.' }).optional(),
  order: z.enum(['asc', 'desc'], { error: 'Order must be asc or desc.' }).optional(),
})

/** Every error the API returns: a message, plus per-field messages when relevant. */
const errorSchema = z.object({
  error: z.string(),
  fields: z.record(z.string(), z.string()).optional(),
})

// ---------------------------------------------------------------------------
// Store — in-memory, seeded with the original three meals
// ---------------------------------------------------------------------------

let nextId = 1

/** @type {Array<z.infer<typeof mealSchema>>} */
const menu = []

function seed(name, category, price, description) {
  const at = new Date().toISOString()
  menu.push({
    id: nextId++,
    name,
    category,
    price,
    description,
    available: true,
    createdAt: at,
    updatedAt: at,
  })
}

seed('Adobo', 'main', 75, 'Pork belly simmered in soy sauce, vinegar and bay leaves.')
seed('Fried Chicken', 'main', 50, 'Buttermilk-brined thigh, dredged and fried to order.')
seed('Yum Burger', 'main', 70, 'Beef patty, cheese and house sauce on a toasted bun.')

const findMeal = (id) => menu.find((meal) => meal.id === id)

/** The message every "no such meal" response uses. */
const missingMeal = (id) => ({ error: `No menu item with ID ${id}.` })

// ---------------------------------------------------------------------------
// The frontend
// ---------------------------------------------------------------------------

// Read per request, so editing index.html shows up without restarting the server.
const INDEX_HTML_PATH = fileURLToPath(new URL('./index.html', import.meta.url))

function indexResponse() {
  const html = readFileSync(INDEX_HTML_PATH, 'utf8')

  return new Response(html, {
    headers: {
      'content-type': 'text/html; charset=utf-8',
      'content-length': String(Buffer.byteLength(html)),
    },
  })
}

// ---------------------------------------------------------------------------
// App
// ---------------------------------------------------------------------------

// Elysia serves through Bun.serve on Bun, but needs the Node adapter on Node.
const adapter =
  typeof Bun === 'undefined' ? (await import('@elysiajs/node')).node() : undefined

new Elysia(adapter ? { adapter } : {})
  .use(
    openapi({
      path: '/openapi',
      // zod -> JSON Schema, so the docs describe the real schemas.
      mapJsonSchema: { zod: z.toJSONSchema },
      documentation: {
        info: {
          title: 'Meal API',
          version: '1.0.0',
          description:
            'A small food menu API. A meal is one item on the menu; /api/menu is the collection.',
        },
        tags: [
          { name: 'Menu', description: 'Browse, create, update and delete meals.' },
        ],
      },
    }),
  )

  // Turn every zod validation failure into one consistent error shape.
  // Elysia defaults to 422 here; we answer 400 with the first message plus
  // a field-by-field breakdown the frontend can render next to each input.
  .onError(({ code, error, status }) => {
    if (code === 'VALIDATION') {
      const issues = (error.all ?? []).map((issue) => ({
        key: typeof issue.path === 'string' ? issue.path : issue.path?.[0],
        message: issue.message,
      }))

      const fields = {}
      for (const { key, message } of issues) {
        if (typeof key === 'string' && !(key in fields)) fields[key] = message
      }

      return status(400, { error: issues[0]?.message ?? 'Invalid request.', fields })
    }

    if (code === 'NOT_FOUND') return status(404, 'Not found')

    console.error('Unhandled error:', error)
    return status(500, { error: 'Internal server error.' })
  })

  // ---- Read -----------------------------------------------------------------

  // GET /api/menu -> the whole menu, optionally filtered and sorted
  .get(
    '/api/menu',
    ({ query }) => {
      let items = [...menu]

      if (query.category) items = items.filter((meal) => meal.category === query.category)
      if (query.available !== undefined) {
        items = items.filter((meal) => meal.available === query.available)
      }

      if (query.search) {
        const needle = query.search.toLowerCase()
        items = items.filter(
          (meal) =>
            meal.name.toLowerCase().includes(needle) ||
            meal.description.toLowerCase().includes(needle),
        )
      }

      if (query.sort) {
        const direction = query.order === 'desc' ? -1 : 1
        items.sort((a, b) => {
          const left = a[query.sort]
          const right = b[query.sort]
          if (left === right) return 0
          return (left > right ? 1 : -1) * direction
        })
      }

      return items
    },
    {
      query: mealQuerySchema,
      response: { 200: z.array(mealSchema) },
      detail: {
        summary: 'List meals',
        description: 'Returns every meal. Supports category, availability, search, sort and order.',
        tags: ['Menu'],
      },
    },
  )

  // GET /api/menu/:id -> one meal
  .get(
    '/api/menu/:id',
    ({ params: { id }, status }) => {
      const meal = findMeal(id)
      if (!meal) return status(404, missingMeal(id))
      return meal
    },
    {
      params: z.object({ id: mealIdSchema }),
      response: { 200: mealSchema, 404: errorSchema },
      detail: { summary: 'Get one meal', tags: ['Menu'] },
    },
  )

  // ---- Create ---------------------------------------------------------------

  // POST /api/menu -> add a meal
  .post(
    '/api/menu',
    ({ body, set, status }) => {
      const at = new Date().toISOString()

      const meal = {
        id: nextId++,
        name: body.name,
        category: body.category,
        price: body.price,
        description: body.description ?? '',
        available: body.available ?? true,
        createdAt: at,
        updatedAt: at,
      }

      menu.push(meal)
      set.headers.location = `/api/menu/${meal.id}`

      return status(201, meal)
    },
    {
      body: mealDraftSchema,
      response: { 201: mealSchema, 400: errorSchema },
      detail: { summary: 'Create a meal', tags: ['Menu'] },
    },
  )

  // ---- Update ---------------------------------------------------------------

  // PUT /api/menu/:id -> replace a meal (omitted optional fields reset)
  .put(
    '/api/menu/:id',
    ({ params: { id }, body, status }) => {
      const index = menu.findIndex((meal) => meal.id === id)
      if (index === -1) return status(404, missingMeal(id))

      const replaced = {
        id,
        name: body.name,
        category: body.category,
        price: body.price,
        description: body.description ?? '',
        available: body.available ?? true,
        createdAt: menu[index].createdAt,
        updatedAt: new Date().toISOString(),
      }

      menu[index] = replaced
      return replaced
    },
    {
      params: z.object({ id: mealIdSchema }),
      body: mealDraftSchema,
      response: { 200: mealSchema, 404: errorSchema },
      detail: { summary: 'Replace a meal', tags: ['Menu'] },
    },
  )

  // PATCH /api/menu/:id -> update only the fields you send
  .patch(
    '/api/menu/:id',
    ({ params: { id }, body, status }) => {
      const index = menu.findIndex((meal) => meal.id === id)
      if (index === -1) return status(404, missingMeal(id))

      const updated = {
        ...menu[index],
        ...body,
        id,
        createdAt: menu[index].createdAt,
        updatedAt: new Date().toISOString(),
      }

      menu[index] = updated
      return updated
    },
    {
      params: z.object({ id: mealIdSchema }),
      body: mealPatchSchema,
      response: { 200: mealSchema, 404: errorSchema },
      detail: { summary: 'Update a meal', tags: ['Menu'] },
    },
  )

  // ---- Delete ---------------------------------------------------------------

  // DELETE /api/menu/:id -> remove a meal
  .delete(
    '/api/menu/:id',
    ({ params: { id }, status }) => {
      const index = menu.findIndex((meal) => meal.id === id)
      if (index === -1) return status(404, missingMeal(id))

      menu.splice(index, 1)
      return status(204)
    },
    {
      params: z.object({ id: mealIdSchema }),
      response: { 404: errorSchema },
      detail: { summary: 'Delete a meal', tags: ['Menu'] },
    },
  )

  // ---- Frontend -------------------------------------------------------------

  .get('/', indexResponse, { detail: { hide: true } })
  .get('/index.html', indexResponse, { detail: { hide: true } })

  .get('*', () => status(404, 'Not found'), { detail: { hide: true } })

  .listen(PORT)

const runtime = typeof Bun === 'undefined' ? 'Node.js' : 'Bun'
console.log(`Meal API running at http://localhost:${PORT} (${runtime})`)
console.log(`API docs at http://localhost:${PORT}/openapi`)