/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
/**
 * Represents the header configuration options for an HTTP request.
 * Instances are immutable. Modifying methods return a cloned
 * instance with the change. The original object is never changed.
 *
 * @publicApi
 */
export class HttpHeaders {
    /**  Constructs a new HTTP header object with the given values.*/
    constructor(headers) {
        /**
         * Internal map of lowercased header names to the normalized
         * form of the name (the form seen first).
         */
        this.normalizedNames = new Map();
        /**
         * Queued updates to be materialized the next initialization.
         */
        this.lazyUpdate = null;
        if (!headers) {
            this.headers = new Map();
        }
        else if (typeof headers === 'string') {
            this.lazyInit = () => {
                this.headers = new Map();
                headers.split('\n').forEach(line => {
                    const index = line.indexOf(':');
                    if (index > 0) {
                        const name = line.slice(0, index);
                        const key = name.toLowerCase();
                        const value = line.slice(index + 1).trim();
                        this.maybeSetNormalizedName(name, key);
                        if (this.headers.has(key)) {
                            this.headers.get(key).push(value);
                        }
                        else {
                            this.headers.set(key, [value]);
                        }
                    }
                });
            };
        }
        else if (typeof Headers !== 'undefined' && headers instanceof Headers) {
            this.headers = new Map();
            headers.forEach((values, name) => {
                this.setHeaderEntries(name, values);
            });
        }
        else {
            this.lazyInit = () => {
                if (typeof ngDevMode === 'undefined' || ngDevMode) {
                    assertValidHeaders(headers);
                }
                this.headers = new Map();
                Object.entries(headers).forEach(([name, values]) => {
                    this.setHeaderEntries(name, values);
                });
            };
        }
    }
    /**
     * Checks for existence of a given header.
     *
     * @param name The header name to check for existence.
     *
     * @returns True if the header exists, false otherwise.
     */
    has(name) {
        this.init();
        return this.headers.has(name.toLowerCase());
    }
    /**
     * Retrieves the first value of a given header.
     *
     * @param name The header name.
     *
     * @returns The value string if the header exists, null otherwise
     */
    get(name) {
        this.init();
        const values = this.headers.get(name.toLowerCase());
        return values && values.length > 0 ? values[0] : null;
    }
    /**
     * Retrieves the names of the headers.
     *
     * @returns A list of header names.
     */
    keys() {
        this.init();
        return Array.from(this.normalizedNames.values());
    }
    /**
     * Retrieves a list of values for a given header.
     *
     * @param name The header name from which to retrieve values.
     *
     * @returns A string of values if the header exists, null otherwise.
     */
    getAll(name) {
        this.init();
        return this.headers.get(name.toLowerCase()) || null;
    }
    /**
     * Appends a new value to the existing set of values for a header
     * and returns them in a clone of the original instance.
     *
     * @param name The header name for which to append the values.
     * @param value The value to append.
     *
     * @returns A clone of the HTTP headers object with the value appended to the given header.
     */
    append(name, value) {
        return this.clone({ name, value, op: 'a' });
    }
    /**
     * Sets or modifies a value for a given header in a clone of the original instance.
     * If the header already exists, its value is replaced with the given value
     * in the returned object.
     *
     * @param name The header name.
     * @param value The value or values to set or override for the given header.
     *
     * @returns A clone of the HTTP headers object with the newly set header value.
     */
    set(name, value) {
        return this.clone({ name, value, op: 's' });
    }
    /**
     * Deletes values for a given header in a clone of the original instance.
     *
     * @param name The header name.
     * @param value The value or values to delete for the given header.
     *
     * @returns A clone of the HTTP headers object with the given value deleted.
     */
    delete(name, value) {
        return this.clone({ name, value, op: 'd' });
    }
    maybeSetNormalizedName(name, lcName) {
        if (!this.normalizedNames.has(lcName)) {
            this.normalizedNames.set(lcName, name);
        }
    }
    init() {
        if (!!this.lazyInit) {
            if (this.lazyInit instanceof HttpHeaders) {
                this.copyFrom(this.lazyInit);
            }
            else {
                this.lazyInit();
            }
            this.lazyInit = null;
            if (!!this.lazyUpdate) {
                this.lazyUpdate.forEach(update => this.applyUpdate(update));
                this.lazyUpdate = null;
            }
        }
    }
    copyFrom(other) {
        other.init();
        Array.from(other.headers.keys()).forEach(key => {
            this.headers.set(key, other.headers.get(key));
            this.normalizedNames.set(key, other.normalizedNames.get(key));
        });
    }
    clone(update) {
        const clone = new HttpHeaders();
        clone.lazyInit =
            (!!this.lazyInit && this.lazyInit instanceof HttpHeaders) ? this.lazyInit : this;
        clone.lazyUpdate = (this.lazyUpdate || []).concat([update]);
        return clone;
    }
    applyUpdate(update) {
        const key = update.name.toLowerCase();
        switch (update.op) {
            case 'a':
            case 's':
                let value = update.value;
                if (typeof value === 'string') {
                    value = [value];
                }
                if (value.length === 0) {
                    return;
                }
                this.maybeSetNormalizedName(update.name, key);
                const base = (update.op === 'a' ? this.headers.get(key) : undefined) || [];
                base.push(...value);
                this.headers.set(key, base);
                break;
            case 'd':
                const toDelete = update.value;
                if (!toDelete) {
                    this.headers.delete(key);
                    this.normalizedNames.delete(key);
                }
                else {
                    let existing = this.headers.get(key);
                    if (!existing) {
                        return;
                    }
                    existing = existing.filter(value => toDelete.indexOf(value) === -1);
                    if (existing.length === 0) {
                        this.headers.delete(key);
                        this.normalizedNames.delete(key);
                    }
                    else {
                        this.headers.set(key, existing);
                    }
                }
                break;
        }
    }
    setHeaderEntries(name, values) {
        const headerValues = (Array.isArray(values) ? values : [values]).map((value) => value.toString());
        const key = name.toLowerCase();
        this.headers.set(key, headerValues);
        this.maybeSetNormalizedName(name, key);
    }
    /**
     * @internal
     */
    forEach(fn) {
        this.init();
        Array.from(this.normalizedNames.keys())
            .forEach(key => fn(this.normalizedNames.get(key), this.headers.get(key)));
    }
}
/**
 * Verifies that the headers object has the right shape: the values
 * must be either strings, numbers or arrays. Throws an error if an invalid
 * header value is present.
 */
function assertValidHeaders(headers) {
    for (const [key, value] of Object.entries(headers)) {
        if (!(typeof value === 'string' || typeof value === 'number') && !Array.isArray(value)) {
            throw new Error(`Unexpected value of the \`${key}\` header provided. ` +
                `Expecting either a string, a number or an array, but got: \`${value}\`.`);
        }
    }
}
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