/**
 * Shared state lives in stores, not prop-drilling (spec §8.2 rule 3).
 * Mutation flow: component → api.js → update store from the response.
 * Svelte 5 runes style only (spec §8.2 rule 8).
 */

import { api } from './api.js'
import { shiftDate } from './format.js'

/** Return today as a YYYY-MM-DD string — the server never decides "today" (spec §8.1 rule 8). */
function todayString() {
  return new Date().toISOString().slice(0, 10)
}

// ── Current date ────────────────────────────────────────────────────────────

export const currentDate = $state({ value: todayString() })

export function setDate(dateStr) {
  currentDate.value = dateStr
}

export function goPrevDay() {
  currentDate.value = shiftDate(currentDate.value, -1)
}

export function goNextDay() {
  currentDate.value = shiftDate(currentDate.value, 1)
}

// ── App view ─────────────────────────────────────────────────────────────────

export const appView = $state({ current: 'dashboard' })

/** Simple navigation requests from child components (e.g., "Set a target"). */
export const navigateTo = (view) => { appView.current = view }

// ── Day data (log + summary) ─────────────────────────────────────────────────

export const dayData = $state({
  log: [],
  summary: null, // { date, totals: { calories, protein_g, ... }, target: {...} | null }
  loading: false,
  error: null,
})

export async function refreshDayData() {
  const date = currentDate.value
  dayData.loading = true
  dayData.error = null
  try {
    const [log, summary] = await Promise.all([
      api.getLog(date),
      api.getSummary(date),
    ])
    dayData.log = log
    dayData.summary = summary
    dayData.loading = false
  } catch (e) {
    dayData.error = e.message
    dayData.loading = false
  }
}

/** Re-fetch the summary for the current date without touching the log array. */
async function refreshSummary() {
  try {
    dayData.summary = await api.getSummary(currentDate.value)
  } catch {
    // Keep the previous summary on failure; the user can retry.
  }
}

/** Add a newly-created log entry to the store then refresh the summary. */
export async function addLogEntryToStore(entry) {
  dayData.log = [...dayData.log, entry]
  await refreshSummary()
}

/** Update a log entry in the store after a successful API PUT, then refresh the summary. */
export async function updateLogEntryInStore(updated) {
  dayData.log = dayData.log.map(e => (e.id === updated.id ? updated : e))
  await refreshSummary()
}

/** Remove a log entry from the store after a successful API DELETE, then refresh the summary. */
export async function removeLogEntryFromStore(id) {
  dayData.log = dayData.log.filter(e => e.id !== id)
  await refreshSummary()
}