<!--
	DrCr: Double-entry bookkeeping framework
	Copyright (C) 2022-2025  Lee Yingtong Li (RunasSudo)
	
	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU Affero General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.
	
	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU Affero General Public License for more details.
	
	You should have received a copy of the GNU Affero General Public License
	along with this program.  If not, see <https://www.gnu.org/licenses/>.
-->

<template>
	<DynamicReportComponent :report="report" :columns="reportColumns">
		<div class="my-2 py-2 flex gap-x-2 items-baseline">
			<input type="date" class="bordered-field" v-model.lazy="dtStart">
			<span>to</span>
			<input type="date" class="bordered-field" v-model.lazy="dt">
			<span>Compare</span>
			<div class="relative flex flex-grow items-stretch shadow-sm">
				<input type="number" min="1" class="bordered-field w-[9.5em] pr-[6em]" v-model.lazy="comparePeriods">
				<div class="absolute inset-y-0 right-0 flex items-center z-10">
					<select class="h-full border-0 bg-transparent py-0 pl-2 pr-8 text-gray-900 focus:ring-2 focus:ring-inset focus:ring-emerald-600" v-model="compareUnit" @change="onCompareUnitChange">
						<option value="years">years</option>
						<option value="months">months</option>
					</select>
				</div>
			</div>
			<DynamicReportMenu :report="report" :columns="reportColumns" :subtitle="dtStart + ' to ' + dt" />
		</div>
	</DynamicReportComponent>
</template>

<script setup lang="ts">
	import dayjs from 'dayjs';
	import { invoke } from '@tauri-apps/api/core';
	import { ref, watch } from 'vue';
	
	import { DynamicReport } from './base.ts';
	import { db } from '../db.ts';
	import DynamicReportComponent from '../components/DynamicReportComponent.vue';
	import DynamicReportMenu from '../components/DynamicReportMenu.vue';
	
	const report = ref(null as DynamicReport | null);
	const reportColumns = ref([] as string[]);
	
	const dt = ref(null as string | null);
	const dtStart = ref(null as string | null);
	
	const comparePeriods = ref(1);
	const compareUnit = ref('years');
	
	async function load() {
		await db.load();
		
		dt.value = db.metadata.eofy_date;
		dtStart.value = dayjs(db.metadata.eofy_date).subtract(1, 'year').add(1, 'day').format('YYYY-MM-DD');
		
		await updateReport();
		
		// Update report when dates etc. changed
		// We initialise the watcher here only after dt and dtStart are initialised above
		watch([dt, dtStart, comparePeriods, compareUnit], updateReport);
	}
	
	async function updateReport() {
		const dayjsDt = dayjs(dt.value!);
		const dayjsDtStart = dayjs(dtStart.value!);
		
		const reportDates = [];
		let newReportColumns = [];
		
		for (let i = 0; i < comparePeriods.value; i++) {
			let thisReportDt, thisReportDtStart;
			
			// Get period start and end dates
			if (compareUnit.value === 'years') {
				thisReportDt = dayjsDt.subtract(i, 'year');
				thisReportDtStart = dayjsDtStart.subtract(i, 'year');
				newReportColumns.push(thisReportDt.format('YYYY'));
			} else if (compareUnit.value === 'months') {
				if (dayjsDt.add(1, 'day').isSame(dayjsDt.set('date', 1).add(1, 'month'))) {
					// If dt is the end of a calendar month, then fix each prior dt to be the end of the calendar month
					thisReportDt = dayjsDt.subtract(i, 'month').set('date', 1).add(1, 'month').subtract(1, 'day');
					thisReportDtStart = dayjsDtStart.subtract(i, 'month');
				} else {
					thisReportDt = dayjsDt.subtract(i, 'month');
					thisReportDtStart = dayjsDtStart.subtract(i, 'month');
				}
				newReportColumns.push(thisReportDt.format('YYYY-MM'));
			} else {
				throw new Error('Unexpected compareUnit');
			}
			
			reportDates.push([thisReportDtStart.format('YYYY-MM-DD'), thisReportDt.format('YYYY-MM-DD')]);
		}
		
		if (comparePeriods.value === 1) {
			// Override column headers if only one column
			newReportColumns = ['$'];
		}
		
		report.value = DynamicReport.fromJSON(await invoke('get_income_statement', { dates: reportDates }));
		reportColumns.value = newReportColumns;  // Wait until report available to update this
	}
	
	load();
	
	function onCompareUnitChange() {
		const dayjsDt = dayjs(dt.value!);
		const dayjsDtStart = dayjs(dtStart.value!);
		
		if (compareUnit.value === 'years') {
			if (dayjsDt.add(1, 'day').subtract(1, 'month').isSame(dayjsDtStart)) {
				// Dates were previously set to one month - now compareUnit changed to years
				// Automatically change dates to one year
				dtStart.value = dayjsDt.add(1, 'day').subtract(1, 'year').format('YYYY-MM-DD');
			}
		} else if (compareUnit.value === 'months') {
			if (dayjsDt.add(1, 'day').subtract(1, 'year').isSame(dayjsDtStart)) {
				// Dates were previously set to one year - now compareUnit changed to months
				// Automatically change dates to one month
				dtStart.value = dayjsDt.add(1, 'day').subtract(1, 'month').format('YYYY-MM-DD');
			}
		} else {
			throw new Error('Unexpected compareUnit');
		}
	}
</script>
