/** Tridactyl normal mode:

    differs from Vim in that no map may be a prefix of another map (e.g. 'g' and 'gg' cannot both be maps). This simplifies the parser.
*/

// Normal-mode mappings.
// keystr -> ex_str
// TODO: Move these into a tridactyl-wide state namespace
// TODO: stop stealing keys from "insert mode"
//          r -> refresh page is particularly unhelpful
//  Can't stringify a map -> just use an object
let nmaps = {
    "o": "fillcmdline open",
    "O": "current_url open",
    "w": "fillcmdline winopen",
    "W": "current_url winopen",
    "t": "tabopen",
    //["t": "fillcmdline tabopen", // for now, use mozilla completion
    "]]": "clicknext", 
    "[[": "clicknext prev", 
    "T": "current_url tabopen",
    "yy": "clipboard yank",
    "p": "clipboard open",
    "P": "clipboard tabopen",
    "j": "scrollline 10",
    "k": "scrollline -10",
    "h": "scrollpx -50",
    "l": "scrollpx 50",
    "G": "scrollto 100",
    "gg": "scrollto 0",
    "H": "back",
    "L": "forward",
    "d": "tabclose",
    "u": "undo",
    "r": "reload",
    "R": "reloadhard",
    "gt": "tabnext",
    "gT": "tabprev",
    "gr": "reader",
    ":": "fillcmdline",
    "s": "fillcmdline open google",
    "S": "fillcmdline tabopen google",
    "xx": "something",
    "i": "insertmode",
    "b": "openbuffer",
    "ZZ": "qall",
    "f": "hint",
    // Special keys must be prepended with 🄰
    // ["🄰Backspace", "something"],
}

// Allow config to be changed in settings
// TODO: make this more general
browser.storage.sync.get("nmaps").then(lazyloadconfig)
async function lazyloadconfig(config_obj){
    let nmaps_config = config_obj["nmaps"]
    nmaps_config = (nmaps_config == undefined) ? {} : nmaps_config
    nmaps = merge_objects(nmaps, nmaps_config)
    console.log(nmaps)
}

browser.storage.onChanged.addListener(
    (changes, areaname) => {
        if (areaname == "sync") {
            browser.storage.sync.get("nmaps").then(lazyloadconfig)
        }
    })

// Shamelessly copied from https://plainjs.com/javascript/utilities/merge-two-javascript-objects-19/
// It should be possible to replace this with Object.assign, but that doesn't seem to work :/
function merge_objects(obj,src){
        Object.keys(src).forEach(function(key) { obj[key] = src[key]; });
        return obj;
}

// Split a string into a number prefix and some following keys.
function keys_split_count(keys: string[]){
    // Extracts the first number with capturing parentheses
    const FIRST_NUM_REGEX = /^([0-9]+)/

    let keystr = keys.join("")
    let regexCapture = FIRST_NUM_REGEX.exec(keystr)
    let count = regexCapture ? regexCapture[0] : null
    keystr = keystr.replace(FIRST_NUM_REGEX,"")
    return [count, keystr]
}

// Given a valid keymap, resolve it to an ex_str
function resolve_map(map) {
    // TODO: This needs to become recursive to allow maps to be defined in terms of other maps.
    return nmaps[map]
}

// Valid keystr to ex_str by splitting count, resolving keystr and appending count as final argument.
// TODO: This is a naive way to deal with counts and won't work for ExCmds that don't expect a numeric answer.
// TODO: Refactor to return a ExCmdPartial object?
function get_ex_str(keys): string {
    let [count, keystr] = keys_split_count(keys)
    let ex_str = resolve_map(keystr)
    if (ex_str){
        ex_str = count ? ex_str + " " + count : ex_str
    }
    return ex_str
}

// A list of maps that keys could potentially map to.
function possible_maps(keys): string[] {
    let [count, keystr] = keys_split_count(keys)

    // Short circuit or search maps.
    if (nmaps.hasOwnProperty(keystr)) {
        return [keystr,]
    } else {
        // Efficiency: this can be short-circuited.
        return completions(keystr)
    }
}

// A list of maps that start with the fragment.
export function completions(fragment): string[] {
    let posskeystrs = Array.from(Object.keys(nmaps))
    return posskeystrs.filter((key)=>key.startsWith(fragment))
}

export interface NormalResponse {
    keys?: string[]
    ex_str?: string
}

export function parser(keys): NormalResponse {
    // If there aren't any possible matches, throw away keys until there are
    while ((possible_maps(keys).length == 0) && (keys.length)) {
        keys = keys.slice(1)
    }

    // If keys map to an ex_str, send it
    let ex_str = get_ex_str(keys)
    if (ex_str){
        return {ex_str}
    }
    // Otherwise, return the keys that might be used in a future command
    return {keys}
}