background.js

/*
This file is part of Talkie -- text-to-speech browser extension button.
<https://github.com/joelpurra/talkie>

Copyright (c) 2016, 2017 Joel Purra <https://joelpurra.com/>

Talkie is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Talkie 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with Talkie.  If not, see <https://www.gnu.org/licenses/>.
*/

/* global chrome:false, window:false, console:false, Promise:false, SpeechSynthesisUtterance:false */

// https://dvcs.w3.org/hg/speech-api/raw-file/tip/speechapi.html#tts-section
// https://dvcs.w3.org/hg/speech-api/raw-file/tip/speechapi.html#examples-synthesis
// https://developer.mozilla.org/en-US/docs/Web/API/Web_Speech_API/Using_the_Web_Speech_API#Speech_synthesis
const extensionShortName = chrome.i18n.getMessage("extensionShortName");

const log = (...args) => {
    const now = new Date().toISOString();

    /* eslint-disable no-console */
    console.log(now, extensionShortName, ...args);
    /* eslint-enable no-console */
};

const logError = (...args) => {
    const now = new Date().toISOString();

    /* eslint-disable no-console */
    console.error(now, extensionShortName, ...args);
    /* eslint-enable no-console */
};

log("Start", "Loading code");

log("Locale", chrome.i18n.getMessage("@@ui_locale"));

const promiseTry = (fn) => new Promise(
    (resolve, reject) => {
        try {
            const result = fn();

            resolve(result);
        } catch (error) {
            reject(error);
        }
    }
);

const shallowCopy = (...objs) => Object.assign({}, ...objs);

const isUndefinedOrNullOrEmptyOrWhitespace = (str) => !(str && typeof str === "string" && str.length > 0 && str.trim().length > 0);

const noTextSelectedMessage = {
    text: chrome.i18n.getMessage("noTextSelectedMessage"),
    effectiveLanguage: chrome.i18n.getMessage("@@ui_locale"),
};

const noVoiceForLanguageDetectedMessage = {
    text: chrome.i18n.getMessage("noVoiceForLanguageDetectedMessage"),
    effectiveLanguage: chrome.i18n.getMessage("noVoiceForLanguageDetectedMessageLanguage"),
};

const setup = () => promiseTry(
    () => {
        log("Start", "Pre-requisites check");

        if (!("speechSynthesis" in window) || typeof window.speechSynthesis.getVoices !== "function" || typeof window.speechSynthesis.speak !== "function") {
            throw new Error("The browser does not support speechSynthesis.");
        }

        if (!("SpeechSynthesisUtterance" in window)) {
            throw new Error("The browser does not support SpeechSynthesisUtterance.");
        }

        log("Done", "Pre-requisites check");
    })
    .then(() => new Promise(
        (resolve, reject) => {
            try {
                log("Start", "Speech synthesizer check");

                // NOTE: the speech synthesizer can only be used after the voices have been loaded.
                const synthesizer = window.speechSynthesis;

                const handleVoicesChanged = () => {
                    delete synthesizer.onerror;
                    delete synthesizer.onvoiceschanged;

                    log("Variable", "synthesizer", synthesizer);

                    log("Done", "Speech synthesizer check");

                    return resolve(synthesizer);
                };

                const handleError = (event) => {
                    delete synthesizer.onerror;
                    delete synthesizer.onvoiceschanged;

                    logError("Error", "Speech synthesizer check", event);

                    return reject(null);
                };

                synthesizer.onerror = handleError;
                synthesizer.onvoiceschanged = handleVoicesChanged;
            } catch (error) {
                return reject(error);
            }
        }
    ))
    .then((synthesizer) => {
        log("Start", "Voices check");

        const voices = synthesizer.getVoices();

        if (!voices || voices.length === 0) {
            throw new Error("The browser does not have any voices installed.");
        }

        log("Variable", "voices[]", voices.length, voices.map(voice => {
            return {
                name: voice.name,
                lang: voice.lang,
            };
        }));

        log("Done", "Voices check");

        return synthesizer;
    })
    .then((synthesizer) => {
        const unload = () => {
            log("Start", "Unloading");

            if (synthesizer.speaking) {
                // Clear all text.
                // TODO: check if the text was added by this extension, or something else.
                synthesizer.cancel();

                // Reset the system to resume playback, just to be nice to the world.
                synthesizer.resume();
            }

            log("Done", "Unloading");
        };

        chrome.runtime.onSuspend.addListener(unload);

        return synthesizer;
    }
);

const speak = (synthesizer, text, language) => executeAddOnBeforeUnloadHandlers()
    .then(() => executeSetTalkieIsSpeaking())
    .then(() => new Promise(
    (resolve, reject) => {
        try {
            log("Start", `Speak text (length ${text.length}): "${text}"`);

            const utterance = new SpeechSynthesisUtterance(text);

            // NOTE: while there might be more than one voice for the particular lanugage, let the browser pick which one.
            utterance.lang = language;

            // TODO: options for per-language voice , pitch, rate?
            // utterance.pitch = [0,2];
            // utterance.rate = [0.1,10];
            // utterance.voice = synthesizer.getVoices()[4];

            log("Variable", "utterance", utterance);

            const handleEnd = (event) => {
                delete utterance.onend;
                delete utterance.onerror;

                log("End", `Speak text (length ${text.length}) spoken in ${event.elapsedTime} milliseconds.`);

                return resolve();
            };

            const handleError = (event) => {
                delete utterance.onend;
                delete utterance.onerror;

                logError("Error", `Speak text (length ${text.length})`, event);

                return reject();
            };

            utterance.onend = handleEnd;
            utterance.onerror = handleError;

            // The actual act of speaking the text.
            synthesizer.speak(utterance);

            if (synthesizer.paused) {
                synthesizer.resume();
            }

            log("Variable", "synthesizer", synthesizer);

            log("Done", `Speak text (length ${text.length})`);
        } catch (error) {
            return reject(error);
        }
    }))
    .then(() => executeSetTalkieIsNotSpeaking()
);

const executeScript = (code) => new Promise(
    (resolve, reject) => {
        try {
            log("About to execute code in page context", code);

            chrome.tabs.executeScript(
                {
                    allFrames: true,
                    matchAboutBlank: true,
                    code: code,
                },
                (result) => {
                    if (chrome.runtime.lastError) {
                        return reject(chrome.runtime.lastError);
                    }

                    return resolve(result);
                }
            );
        } catch (error) {
            return reject(error);
        }
    }
);

const executeSetTalkieIsSpeakingCode = "window.talkieIsSpeaking = true;";
const executeSetTalkieIsSpeaking = () => executeScript(executeSetTalkieIsSpeakingCode);

const executeSetTalkieIsNotSpeakingCode = "window.talkieIsSpeaking = false;";
const executeSetTalkieIsNotSpeaking = () => executeScript(executeSetTalkieIsNotSpeakingCode);

const executeAddOnBeforeUnloadHandlersCode = "window.talkieIsSpeaking === undefined && window.addEventListener(\"beforeunload\", function () { window.talkieIsSpeaking === true && window.speechSynthesis.cancel(); });";
const executeAddOnBeforeUnloadHandlers = () => executeScript(executeAddOnBeforeUnloadHandlersCode);

const executeGetFramesSelectionTextAndLanguageCode = "function talkieGetParentElementLanguages(element) { return [].concat(element && element.getAttribute(\"lang\")).concat(element.parentElement && talkieGetParentElementLanguages(element.parentElement)); }; var talkieSelectionData = { text: document.getSelection().toString(), htmlTagLanguage: document.getElementsByTagName(\"html\")[0].getAttribute(\"lang\"), parentElementsLanguages: talkieGetParentElementLanguages(document.getSelection().rangeCount > 0 && document.getSelection().getRangeAt(0).startContainer.parentElement) }; talkieSelectionData";
const executeGetFramesSelectionTextAndLanguage = () => executeScript(executeGetFramesSelectionTextAndLanguageCode).then((framesSelectionTextAndLanguage) => {
    log("Variable", "framesSelectionTextAndLanguage", framesSelectionTextAndLanguage);

    return framesSelectionTextAndLanguage;
});

const detectPageLanguage = () => new Promise(
    (resolve, reject) => {
        try {
            chrome.tabs.detectLanguage((language) => {
                // https://developer.chrome.com/extensions/tabs#method-detectLanguage
                if (chrome.runtime.lastError) {
                    return reject(chrome.runtime.lastError);
                }

                log("detectPageLanguage", "Browser detected primary page language", language);

                // The language fallback value is "und", so treat it as no language.
                if (!language || typeof language !== "string" || language === "und") {
                    return resolve(null);
                }

                return resolve(language);
            });
        } catch (error) {
            return reject(error);
        }
    }
);

const detectTextLanguage = (text) => new Promise(
    (resolve, reject) => {
        try {
            if (!("detectLanguage" in chrome.i18n)) {
                // NOTE: text-based language detection is only used as a fallback.
                log("detectTextLanguage", "Browser does not support detecting text language");

                return resolve(null);
            }

            chrome.i18n.detectLanguage(text, (result) => {
                // https://developer.chrome.com/extensions/i18n#method-detectLanguage
                if (chrome.runtime.lastError) {
                    return reject(chrome.runtime.lastError);
                }

                // The language fallback value is "und", so treat it as no language.
                if (
                    !result.isReliable
                    || !result.languages
                    || !(result.languages.length > 0)
                    || typeof result.languages[0].language !== "string"
                    || !(result.languages[0].language.trim().length > 0)
                    || result.languages[0].language === "und"
                ) {
                    // NOTE: text-based language detection is only used as a fallback.
                    log("detectTextLanguage", "Browser did not detect reliable text language", result);

                    return resolve(null);
                }

                const primaryDetectedTextLanguage = result.languages[0].language;

                log("detectTextLanguage", "Browser detected reliable text language", result, primaryDetectedTextLanguage);

                return resolve(primaryDetectedTextLanguage);
            });
        } catch (error) {
            return reject(error);
        }
    }
);

const cleanupSelections = (allVoices, detectedPageLanguage, selections) => promiseTry(
    () => {
        const isNonNullObject = (selection) => !!selection && typeof selection === "object";

        const hasValidText = (selection) => !isUndefinedOrNullOrEmptyOrWhitespace(selection.text);

        const trimText = (selection) => {
            const copy = shallowCopy(selection);

            copy.text = copy.text.trim();

            return copy;
        };

        const selectionsWithValidText = selections
        .filter(isNonNullObject)
        .filter(hasValidText)
        .map(trimText)
        .filter(hasValidText);

        return selectionsWithValidText;
    })
    .then((selectionsWithValidText) => Promise.all(
        selectionsWithValidText.map(
            (selection) => {
                const copy = shallowCopy(selection);

                return detectTextLanguage(copy.text)
                    .then((detectedTextLanguage) => {
                        copy.detectedTextLanguage = detectedTextLanguage;

                        return copy;
                    });
            })
        )
    )
    .then((selectionsWithValidTextAndDetectedLanguage) => {
        const isKnownVoiceLanguage = (elementLanguage) => allVoices.some((voice) => voice.lang.startsWith(elementLanguage));

        // https://www.iso.org/obp/ui/#iso:std:iso:639:-1:ed-1:v1:en
        // https://en.wikipedia.org/wiki/ISO_639-1
        // https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes
        // http://xml.coverpages.org/iso639a.html
        // NOTE: discovered because Twitter seems to still use "iw".
        const iso639Dash1Aliases1988To2002 = {
            "in": "id",
            "iw": "he",
            "ji": "yi",
        };

        const mapIso639Aliases = (language) => {
            return iso639Dash1Aliases1988To2002[language] || language;
        };

        const isValidString = (str) => !isUndefinedOrNullOrEmptyOrWhitespace(str);

        const cleanupLanguagesArray = (languages) => {
            const copy = (languages || [])
            .filter(isValidString)
            .map(mapIso639Aliases)
            .filter(isKnownVoiceLanguage);

            return copy;
        };

        const cleanupParentElementsLanguages = (selection) => {
            const copy = shallowCopy(selection);

            copy.parentElementsLanguages = cleanupLanguagesArray(copy.parentElementsLanguages);

            return copy;
        };

        const getMoreSpecificLanguagesWithPrefix = (prefix) => {
            return (language) => language.startsWith(prefix) && language.length > prefix.length;
        };

        const setEffectiveLanguage = (selection) => {
            const copy = shallowCopy(selection);

            const detectedLanguages = [
                copy.detectedTextLanguage,
                copy.parentElementsLanguages[0] || null,
                copy.htmlTagLanguage,
                detectedPageLanguage,
            ];

            log("setEffectiveLanguage", "detectedLanguages", detectedLanguages);

            const cleanedLanguages = cleanupLanguagesArray(detectedLanguages);

            log("setEffectiveLanguage", "cleanedLanguages", cleanedLanguages);

            const primaryLanguagePrefix = cleanedLanguages[0] || null;

            log("setEffectiveLanguage", "primaryLanguagePrefix", primaryLanguagePrefix);

            // NOTE: if there is a more specific language with the same prefix among the detected languages, prefer it.
            const cleanedLanguagesWithPrimaryPrefix = cleanedLanguages.filter(getMoreSpecificLanguagesWithPrefix(primaryLanguagePrefix));

            log("setEffectiveLanguage", "cleanedLanguagesWithPrimaryPrefix", cleanedLanguagesWithPrimaryPrefix);

            const effectiveLanguage = cleanedLanguagesWithPrimaryPrefix[0] || cleanedLanguages[0] || null;

            log("setEffectiveLanguage", "effectiveLanguage", effectiveLanguage);

            copy.effectiveLanguage = effectiveLanguage;

            return copy;
        };

        const mapResults = (selection) => {
            return {
                text: selection.text,
                effectiveLanguage: selection.effectiveLanguage,
            };
        };

        const fallbackMessageForNoLanguageDetected = (selection) => {
            if (selection.effectiveLanguage === null) {
                return noVoiceForLanguageDetectedMessage;
            }

            return selection;
        };

        const selectionsWithValidTextAndDetectedLanguageAndEffectiveLanguage = selectionsWithValidTextAndDetectedLanguage.map(cleanupParentElementsLanguages)
        .map(setEffectiveLanguage)
        .map(fallbackMessageForNoLanguageDetected)
        .map(mapResults);

        if (selectionsWithValidTextAndDetectedLanguageAndEffectiveLanguage.length === 0) {
            log("Empty filtered selections");

            selectionsWithValidTextAndDetectedLanguageAndEffectiveLanguage.push(noTextSelectedMessage);
        }

        return selectionsWithValidTextAndDetectedLanguageAndEffectiveLanguage;
    }
);

const speakAllSelections = (synthesizer, selections, detectedPageLanguage) => promiseTry(() => {
    log("Start", "Speaking all selections");

    log("Variable", `selections (length ${selections && selections.length || 0})`, selections);

    return promiseTry(() => synthesizer.getVoices())
        .then((allVoices) => cleanupSelections(allVoices, detectedPageLanguage, selections))
        .then((cleanedupSelections) => {
            log("Variable", `cleanedupSelections (length ${cleanedupSelections && cleanedupSelections.length || 0})`, cleanedupSelections);

            const speakPromises = cleanedupSelections.map((selection) => {
                log("Text", `Speaking selection (length ${selection.text.length}, effectiveLanguage ${selection.effectiveLanguage})`, selection);

                return speak(synthesizer, selection.text, selection.effectiveLanguage);
            });

            log("Done", "Speaking all selections");

            return Promise.all(speakPromises);
        });
});

const speakUserSelection = (synthesizer) => promiseTry(() => {
    log("Start", "Speaking selection");

    return Promise.all(
        [
            executeGetFramesSelectionTextAndLanguage(),
            detectPageLanguage(),
        ]
    )
        .then(([framesSelectionTextAndLanguage, detectedPageLanguage]) => {
            return speakAllSelections(synthesizer, framesSelectionTextAndLanguage, detectedPageLanguage);
        })
        .then(() => log("Done", "Speaking selection"));
});

const getIconModePaths = (name) => {
    return {
        "16": `resources/icon/icon-${name}/icon-16x16.png`,
        "32": `resources/icon/icon-${name}/icon-32x32.png`,
        "48": `resources/icon/icon-${name}/icon-48x48.png`,
        "64": `resources/icon/icon-${name}/icon-64x64.png`,
        "128": `resources/icon/icon-${name}/icon-128x128.png`,
        "256": `resources/icon/icon-${name}/icon-256x256.png`,
        "512": `resources/icon/icon-${name}/icon-512x512.png`,
        "1024": `resources/icon/icon-${name}/icon-1024x1024.png`,
    };
};

const setIconMode = (name) => new Promise(
    (resolve, reject) => {
        try {
            log("Start", "Changing icon to", name);

            const paths = getIconModePaths(name);
            const details = {
                path: paths,
            };

            chrome.browserAction.setIcon(
                details,
                () => {
                    if (chrome.runtime.lastError) {
                        return reject(chrome.runtime.lastError);
                    }

                    log("Done", "Changing icon to", name);

                    resolve();
                }
            );
        } catch (error) {
            return reject(error);
        }
    }
);

const setIconModePlaying = () => setIconMode("stop");
const setIconModeStopped = () => setIconMode("play");

(function main() {
    // NOTE: using a chainer to be able to add click-driven speech events one after another.
    let rootChain = Promise.resolve();

    const rootChainCatcher = (error) => {
        logError(error);
    };

    const chain = (promise) => {
        rootChain = rootChain
        .then(promise)
        .catch(rootChainCatcher);
    };

    // NOTE: while not strictly necessary, keep and pass a reference to the global (initialized) synthesizer.
    let synthesizer = null;

    chain(
        () => setup()
            .then((result) => {
                synthesizer = result;

                return undefined;
            })
    );

    const handleIconClick = () => {
        const wasSpeaking = synthesizer.speaking;

        // Clear all old text.
        synthesizer.cancel();

        if (!wasSpeaking) {
            return chain(() => Promise.all(
                [
                    setIconModePlaying(),
                    speakUserSelection(synthesizer),
                ]
            )
                .then(() => setIconModeStopped())
                .catch((error) => {
                    return setIconModeStopped()
                        .then(() => {
                            throw error;
                        });
                }));
        }

        return chain(() => setIconModeStopped());
    };

    chrome.browserAction.onClicked.addListener(handleIconClick);
}());

log("Done", "Loading code");