/**
 * A parsed wardley map.
 * @typedef {Object} Map
 * @property {Entity[]} entities - The list of parsed entities
 */

/**
 * Any of the potential entities in the map.
 * @typedef {Component|Dependency|Note|Stage|Group|Inertia|Evolution} Entity
 */

/**
 * Any of the potential shapes in a component.
 * @typedef {"x"|"square"|"triangle"|"circle"} Shape
 */

/**
 * A component in the map.
 * @typedef {Object} Component
 * @property {'component'} type - Entity type
 * @property {string} label - Component label
 * @property {[number, number]} coordinates - X and Y coordinates
 * @property {Shape} shape - Shape of the component
 */

/**
 * A dependency between two components.
 * @typedef {Object} Dependency
 * @property {'dependency'} type - Entity type
 * @property {string} from - Source component label
 * @property {string} to - Target component label
 * @property {boolean} isDirected - Whether the dependency is directed (->) or undirected (--)
 */

/**
 * A note.
 * @typedef {Object} Note
 * @property {'note'} type - Entity type
 * @property {[number, number]} coordinates - X and Y coordinates
 * @property {string} text - Note text content
 */

/**
 * An override for the width of an evolution stage.
 * @typedef {Object} Stage
 * @property {'stage'} type - Entity type
 * @property {string} stage - Stage number (i, ii, iii, iv)
 * @property {number} value - Stage value
 */

/**
 * A group of components.
 * @typedef {Object} Group
 * @property {'group'} type - Entity type
 * @property {string[]} components - Array of component labels in the group
 */

/**
 * Inertia associated with a component.
 * @typedef {Object} Inertia
 * @property {'inertia'} type - Entity type
 * @property {string} component - Component label with inertia
 */

/**
 * Evolution associated with a component.
 * @typedef {Object} Evolution
 * @property {'evolution'} type - Entity type
 * @property {string} component - Component label
 * @property {number} value - Evolution value
 */

/**
 * Helper: Check if character is whitespace
 */
function isWhitespace(character) {
    return character === " " || character === "\t";
}

/**
 * Helper: Check if character is a digit or dot
 */
function isDigitOrDot(character) {
    return (character >= "0" && character <= "9") || character === ".";
}

/**
 * wmap format Wardley Map parser.
 * @param {string} source - The wmap source code to parse
 * @returns {Map} - Parsed map with entities
 */
export function parse(source) {
    const entities = [];
    const lines = source.split(/\r\n|\r|\n/);

    for (const rawLine of lines) {
        const line = rawLine.trim();
        if (!line) continue;

        const entity = parseLine(line);
        if (entity) {
            entities.push(entity);
        }
    }

    return { entities };
}

/**
 * Parse a line
 */
function parseLine(line) {
    const length = line.length;
    let i = 0;

    // Skip leading whitespace
    while (i < length && isWhitespace(line[i])) i++;
    if (i >= length) return null;

    if (line[i] === "[") {
        return parseKeywordEntity(line, i, length);
    }

    return parseComponentOrDependency(line, length);
}

/**
 * Parse entities that start with keywords in brackets: [Stage], [Note], [Group], [Inertia], [Evolution]
 */
function parseKeywordEntity(line, start, length) {
    let i = start + 1; // skip '['
    const keywordStart = i;

    // Read until ']'
    while (i < length && line[i] !== "]") i++;
    if (i >= length) return null;

    const keyword = line.substring(keywordStart, i).trim().toLowerCase();
    i++; // skip ']'

    // Skip whitespace after ']'
    while (i < length && isWhitespace(line[i])) i++;

    // Stage: [I|II|III|IV] stage
    if (
        keyword === "i" ||
        keyword === "ii" ||
        keyword === "iii" ||
        keyword === "iv"
    ) {
        const numStart = i;
        while (i < length && isDigitOrDot(line[i])) i++;
        if (i > numStart) {
            return {
                type: "stage",
                stage: keyword,
                value: parseFloat(line.substring(numStart, i)),
            };
        }
        return null;
    }

    // Note: [Note] (x, y) text
    if (keyword === "note") {
        // Expect '('
        if (i >= length || line[i] !== "(") return null;
        i++;

        // Read x
        while (i < length && isWhitespace(line[i])) i++;
        const xStart = i;
        while (i < length && isDigitOrDot(line[i])) i++;
        if (i === xStart) return null;
        const x = parseFloat(line.substring(xStart, i));

        // Expect ','
        while (i < length && isWhitespace(line[i])) i++;
        if (i >= length || line[i] !== ",") return null;
        i++;

        // Read y
        while (i < length && isWhitespace(line[i])) i++;
        const yStart = i;
        while (i < length && isDigitOrDot(line[i])) i++;
        if (i === yStart) return null;
        const y = parseFloat(line.substring(yStart, i));

        // Expect ')'
        while (i < length && isWhitespace(line[i])) i++;
        if (i >= length || line[i] !== ")") return null;
        i++;

        // Read text
        while (i < length && isWhitespace(line[i])) i++;
        const text = line.substring(i).trim();

        return {
            type: "note",
            coordinates: [x, y],
            text,
        };
    }

    // Group: [Group] label1, label2, ...
    if (keyword === "group") {
        const components = line
            .substring(i)
            .split(",")
            .map(v => v.trim())
            .filter(v => v);
        return components.length > 0 ? { type: "group", components } : null;
    }

    // Inertia: [Inertia] label
    if (keyword === "inertia") {
        const component = line.substring(i).trim();
        return component ? { type: "inertia", component } : null;
    }

    // Evolution: [Evolution] label +/- number
    if (keyword === "evolution") {
        let indexOfSign = -1;
        let signCharacter = null;

        // Find the sign
        for (let j = i; j < length; j++) {
            if (line[j] === "+" || line[j] === "-") {
                // Make sure it's not part of a dependency arrow
                if (j + 1 < length && (line[j + 1] === ">" || line[j + 1] === "-"))
                    continue;
                indexOfSign = j;
                signCharacter = line[j];
                break;
            }
        }

        if (indexOfSign === -1 || indexOfSign === i) return null;

        const component = line.substring(i, indexOfSign).trim();
        if (!component) return null;

        // Read number after sign
        let indexOfNumber = indexOfSign + 1;
        while (indexOfNumber < length && isWhitespace(line[indexOfNumber])) indexOfNumber++;
        const numStart = indexOfNumber;
        while (indexOfNumber < length && isDigitOrDot(line[indexOfNumber])) indexOfNumber++;
        if (indexOfNumber === numStart) return null;

        return {
            type: "evolution",
            component,
            value: (signCharacter === "+" ? 1 : -1) * parseFloat(line.substring(numStart, indexOfNumber)),
        };
    }

    return null;
}

/**
 * Parse component or dependency
 */
function parseComponentOrDependency(line, length) {
    // Use indexOf to quickly find potential dependency arrows and parentheses
    const indexOfArrow = line.indexOf("->");
    const indexOfDash = line.indexOf("--");
    const indexOfParenthesis = line.indexOf("(");

    // Check for directed dependency (->)
    if (indexOfArrow !== -1 && (indexOfParenthesis === -1 || indexOfArrow < indexOfParenthesis)) {
        const from = line.substring(0, indexOfArrow).trim();
        const to = line.substring(indexOfArrow + 2).trim();
        if (from && to) {
            return {
                type: "dependency",
                from,
                to,
                isDirected: true,
            };
        }
        return null;
    }

    // Check for undirected dependency (--)
    if (indexOfDash !== -1 && (indexOfParenthesis === -1 || indexOfDash < indexOfParenthesis)) {
        const from = line.substring(0, indexOfDash).trim();
        const to = line.substring(indexOfDash + 2).trim();
        if (from && to) {
            return {
                type: "dependency",
                from,
                to,
                isDirected: false,
            };
        }
        return null;
    }

    // Check for component (opening parenthesis)
    if (indexOfParenthesis > 0) {
        return parseComponent(line, indexOfParenthesis, length);
    }

    return null;
}

/**
 * Parse component starting from the opening parenthesis
 */
function parseComponent(line, indexOfParenthesis, length) {
    const label = line.substring(0, indexOfParenthesis).trim();
    if (!label) return null;

    let i = indexOfParenthesis + 1;

    // Read x
    while (i < length && isWhitespace(line[i])) i++;
    const xStart = i;
    while (i < length && isDigitOrDot(line[i])) i++;
    if (i === xStart) return null;
    const x = parseFloat(line.substring(xStart, i));

    // Expect ','
    while (i < length && isWhitespace(line[i])) i++;
    if (i >= length || line[i] !== ",") return null;
    i++;

    // Read y
    while (i < length && isWhitespace(line[i])) i++;
    const yStart = i;
    while (i < length && isDigitOrDot(line[i])) i++;
    if (i === yStart) return null;
    const y = parseFloat(line.substring(yStart, i));

    // Expect ')'
    while (i < length && isWhitespace(line[i])) i++;
    if (i >= length || line[i] !== ")") return null;
    i++;

    // Optional shape: [shape]
    let shape = "circle";
    while (i < length && isWhitespace(line[i])) i++;
    if (i < length && line[i] === "[") {
        i++;
        const shapeStart = i;
        while (i < length && line[i] !== "]") i++;
        if (i > shapeStart && i < length) {
            shape = line.substring(shapeStart, i).trim().toLowerCase();
        }
    }

    return {
        type: "component",
        label,
        coordinates: [x, y],
        shape,
    };
}