// * Packages
import slugify from "slugify";
import pluralize, { singular } from "pluralize";

interface Stringable {
    /**
     * Trim a word based.
     * Examples:
     * - "...Some.$.in.the.GARDEN !..." -> Some $ in the GARDEN !
     *
     * @return Stringable
     */
    trim: () => Stringable;
    /**
     * Slugify a word based.
     * Examples:
     * - Some $ in the GARDEN ! -> some-dollar-in-the-garden
     *
     * @return Stringable
     */
    slug: () => Stringable;
    /**
     * Upper case the first letter of a word based.
     * Examples:
     * - some $ in the GARDEN ! -> Some $ in the GARDEN !
     *
     * @return Stringable
     */
    ucFirst: () => Stringable;
    /**
     * Camel case a word based.
     * Examples:
     * - Some $ in the GARDEN ! -> some$InTheGarden!
     *
     * @return Stringable
     */
    camelCase: () => Stringable;
    /**
     * Pascal case a word based.
     * Examples:
     * - some $ in the GARDEN ! -> Some$InTheGarden!
     *
     * @return Stringable
     */
    pascalCase: () => Stringable;
    /**
     * Kebab case a word based.
     * Examples:
     * - Some $ in the GARDEN ! -> some-$-in-the-garden-!
     *
     * @return Stringable
     */
    kebabCase: () => Stringable;
    /**
     * Snake case a word based.
     * Examples:
     * - Some $ in the GARDEN ! -> some_$_in_the_garden_!
     *
     * @return Stringable
     */
    snakeCase: () => Stringable;
    /**
     * Upper case a word based.
     * Examples:
     * - Some $ in the GARDEN ! -> SOME $ IN THE GARDEN !
     *
     * @return Stringable
     */
    upperCase: () => Stringable;
    /**
     * Lower case a word based.
     * Examples:
     * - Some $ in the GARDEN ! -> some $ in the garden !
     *
     * @return Stringable
     */
    lowerCase: () => Stringable;
    /**
     * Pluralize a word based.
     * Examples:
     * - word -> words
     * - story -> stories
     *
     * @return Stringable
     */
    plural: () => Stringable;
    /**
     * Singularize a word based.
     * Examples:
     * - words -> word
     * - stories -> story
     *
     * @return Stringable
     */
    singular: () => Stringable;
    /**
     * Return the transformated string.
     *
     * @return string
     */
    value: () => string;
}

/**
 * Get a Stringable object.
 *
 * @param string initialValue
 * @return Stringable
 */
const str = (initialValue: string): Stringable => {
    let value = initialValue;

    // * HELPERS

    /**
     * Split string into multiple segments.
     * @param string string
     * @returns string[]
     */
    const splitIntoSegments = (string: string): string[] =>
        string.split(/[-_\s]+/).filter(Boolean);

    // * METHODS

    return {
        trim: (): Stringable => {
            value = value.trim();
            return str(value);
        },

        slug: (): Stringable => {
            value = slugify(value, { lower: true, strict: true, trim: true });
            return str(value);
        },

        ucFirst: (): Stringable => {
            value = value.charAt(0).toUpperCase() + value.slice(1);
            return str(value);
        },

        camelCase: (): Stringable => {
            const segments = splitIntoSegments(value);

            // If segments are empty.
            if (segments.length === 0) {
                value = "";
                return str(value);
            }

            // If single segment and already in camel case.
            if (segments.length === 1 && /^[a-z][a-zA-Z0-9]*$/.test(value)) {
                return str(value);
            }

            // first segment: lower first char, preserve internals
            const first =
                segments[0].charAt(0).toLowerCase() + segments[0].slice(1);

            // rest: uppercase first char; preserve internals if mixed case, otherwise lowercase internals
            const rest = segments.slice(1).map((p) => {
                if (!p) return "";
                const hasLower = /[a-z]/.test(p);
                const hasUpper = /[A-Z]/.test(p);
                const isMixed = hasLower && hasUpper;
                const head = p.charAt(0).toUpperCase();
                const tail = p.slice(1);
                return isMixed ? head + tail : head + tail.toLowerCase();
            });

            value = [first, ...rest].join("");
            return str(value);
        },

        pascalCase: (): Stringable => {
            const segments = splitIntoSegments(value);
            if (segments.length === 0) {
                value = "";
                return str(value);
            }

            // If already Pascal-ish, keep as is
            if (segments.length === 1 && /^[A-Z][a-zA-Z0-9]*$/.test(value)) {
                return str(value);
            }

            const converted = segments.map((p) => {
                const hasLower = /[a-z]/.test(p);
                const hasUpper = /[A-Z]/.test(p);
                const isMixed = hasLower && hasUpper;

                if (isMixed) {
                    // preserve internal capitals, only uppercase first char
                    return p.charAt(0).toUpperCase() + p.slice(1);
                }
                // normalize (capitalize first, lowercase rest)
                return p.charAt(0).toUpperCase() + p.slice(1).toLowerCase();
            });

            value = converted.join("");
            return str(value);
        },

        kebabCase: (): Stringable => {
            const words = value
                .replace(/([a-z0-9])([A-Z])/g, "$1 $2")
                .split(/[-_\s]+/)
                .filter(Boolean);
            value = words.map((w) => w.toLowerCase()).join("-");
            return str(value);
        },

        snakeCase: (): Stringable => {
            const words = value
                .replace(/([a-z0-9])([A-Z])/g, "$1 $2")
                .split(/[-\s]+|_+/)
                .filter(Boolean);

            value = words.map((w) => w.toLowerCase()).join("_");
            return str(value);
        },

        upperCase: (): Stringable => {
            value = value.toUpperCase();
            return str(value);
        },

        lowerCase: (): Stringable => {
            value = value.toLowerCase();
            return str(value);
        },

        plural: (): Stringable => {
            value = pluralize(value);
            return str(value);
        },

        singular: (): Stringable => {
            value = singular(value);
            return str(value);
        },

        value: (): string => value,
    };
};

export default str;