import type { LocaleResolver, GlobLocale } from "./comn_types.ts";
import type { UnitCategoryData, UnitCategoryInstance, UnitCategoryKey, UnitDisplay, UnitInstance, UnitSystem } from "./unit_types.ts";
import { resolveLocale } from "./comn_engine.ts";
import { DEFAULT_ISO_LOCALE } from "@/ling/lib/consts.ts";
import { type LingNode, type LingInstance, ling } from "@/ling/lib";
import { unitData } from "./unit_data.ts";
import { unitsLingNode } from "./unit_langs.ts";





// ==============================
// CONVERSIÓN DE TEMPERATURA
// ==============================

function convertTemp(value: number, from: string, to: string): number {
    if (from === to) return value;
    let c: number;
    switch (from) {
        case 'c': c = value; break;
        case 'f': c = (value - 32) * 5 / 9; break;
        case 'k': c = value - 273.15; break;
        default:  c = value;
    }
    switch (to) {
        case 'c': return c;
        case 'f': return c * 9 / 5 + 32;
        case 'k': return c + 273.15;
        default:  return c;
    }
}

// ==============================
// CATEGORY ENGINE
// ==============================

function createCategory<S extends LingNode>(
    categoryKey  : UnitCategoryKey,
    category     : UnitCategoryData,
    getSystem    : () => UnitSystem,
    defaultLocale: LocaleResolver,
    ling         : LingInstance<S>,
): UnitCategoryInstance {

    function resolveTargetUnit(): string {
        return getSystem() === 'imperial' ? category.baseImperial : category.base;
    }

    function formatValue(value: number, unitKey: string, display: UnitDisplay, locale: GlobLocale): string {
        const formatted = new Intl.NumberFormat(locale, { maximumFractionDigits: 2 }).format(value);

        if (display === 'abbr') {
            // Lee símbolo de ling: units.weight.kg.abbr
            const abbr = ling.t(`units.${categoryKey}.${unitKey}.abbr` as any);
            return `${formatted} ${abbr}`;
        }

        // Lee nombre pluralizado de ling: units.weight.kg.name
        const name = ling.t(`units.${categoryKey}.${unitKey}.name` as any, { count: value });
        return `${formatted} ${name}`;
    }

    function convert(value: number, from: string, to: string): number {
        if (from === to) return value;
        if (categoryKey === 'temp') return convertTemp(value, from, to);
        const fromData = category.units[from];
        const toData   = category.units[to];
        if (!fromData || !toData) return value;
        return (value * fromData.factor) / toData.factor;
    }

    function f(value: number, display: UnitDisplay = 'abbr', locale: LocaleResolver = defaultLocale): string {
        const loc  = resolveLocale(locale);
        const unit = resolveTargetUnit();
        return formatValue(value, unit, display, loc);
    }

    function fTo(value: number, targetUnit?: string, display: UnitDisplay = 'abbr', locale: LocaleResolver = defaultLocale): string {
        const loc       = resolveLocale(locale);
        const to        = targetUnit ?? resolveTargetUnit();
        const converted = convert(value, category.base, to);
        return formatValue(converted, to, display, loc);
    }

    return { f, fTo, convert };
}

// ==============================
// UNIT ENGINE
// ==============================

export function createUnit<S extends LingNode>(
    ling         : LingInstance<S>,
    categories   : Partial<Record<UnitCategoryKey, UnitCategoryData>> = {},
    opts         : { selectedSystem?: UnitSystem } = {},
    defaultLocale: LocaleResolver = 'es'
): UnitInstance {

    // El módulo registra sus propias traducciones en ling
    ling.extend('units', unitsLingNode);

    let currentSystem: UnitSystem = opts.selectedSystem ?? 'metric';

    function getSystem(): UnitSystem  { return currentSystem; }
    function setSystem(s: UnitSystem) { currentSystem = s; }

    const merged: Record<UnitCategoryKey, UnitCategoryData> = {
        ...unitData,
        ...categories,
    };

    const makeCategory = (key: UnitCategoryKey) =>
        createCategory(key, merged[key], getSystem, defaultLocale, ling);

    return {
        getSystem,
        setSystem,
        weight : makeCategory('weight'),
        length : makeCategory('length'),
        temp   : makeCategory('temp'),
        volume : makeCategory('volume'),
        area   : makeCategory('area'),
    };
}