function alias_eval(alias, name, type) {
    text = alias "() { "
    if (type == "function") {
        text = text name " \"${@}\""
    } else if (type == "variable") {
        text = text "echo \"${" name "}\""
    }
    print text "; }"
}

function append(line) {
    if (doc) {
        doc = doc "\n"
    }
    doc = doc line
}

function extract(string, type) {
    if (type == "alias") {
        split(string, array, "#=")
        return trim(array[2])
    } else if (type == "command") {
        split(string, array, "#/")
        return trim(array[2])
    } else if (type == "doc") {
        split(string, array, "#")
        return trim(array[2])
    } else if (type == "function") {
        split(string, array, "(")
        return trim(array[1])
    } else if (type == "module") {
        split(string, array, "#\\.")
        return trim(array[2])
    } else if (type == "shebang") {
        split(string, array, "#!")
        return trim(array[2])
    } else if ((type == "constant") || (type == "variable")) {
        split(string, array, "=")
        return trim(array[1])
    }
}

function output(name, type) {
    print "↙ " type
    print name
    print doc
    exit
}

function reset() {
    if (f == "") {
        doc = ""
    }
}

function trim(string) {
    text = string
    sub("^[\t ]*", "", text)
    sub("[\t ]*$", "", text)
    return text
}

BEGIN {
    RE_ANY = "(.*)"
    RE_BEGIN = "^"
    RE_CONST = "([_A-Z][_0-9A-Z]*)"
    RE_SET = "=.*"
    RE_SPACE = "[[:space:]]"
    RE_TSK = "(FIXME|TODO)"
    RE_VAR = "([_a-z][_0-9a-z]*)"

    RE_SPACES = RE_SPACE "*"

    RE_END = RE_SPACES "$"
    RE_FUNC = RE_SPACES "\\(" RE_SPACES "\\)" RE_SPACES "{"

    re["alias"] = RE_BEGIN "#=" RE_SPACES RE_VAR RE_END
    re["binary"] = RE_BEGIN "#\\|" RE_SPACES RE_VAR RE_END
    RE_CLOSE = RE_BEGIN "}" RE_SPACES RE_END
    re["command"] = RE_BEGIN "#/" RE_SPACES RE_VAR RE_END
    RE_COMMENT = RE_BEGIN "#" RE_ANY RE_END
    re["constant"] = RE_BEGIN RE_CONST RE_SET RE_END
    RE_DOC = RE_BEGIN RE_SPACES "#" RE_SPACE RE_ANY RE_END
    re["function"] = RE_BEGIN RE_VAR RE_FUNC RE_END
    RE_MODULE = RE_BEGIN "#\\." RE_SPACES RE_ANY RE_END
    RE_SHEBANG = RE_BEGIN "#!" RE_SPACES RE_ANY RE_END
    RE_TASK = RE_BEGIN RE_SPACES "#" RE_SPACES RE_TSK RE_ANY RE_END
    re["variable"] = RE_BEGIN RE_VAR RE_SET RE_END

    f = ""
    match_alias = 0
    match_command = 0
    match_module = 0
    match_task = 0
    reset()
}

{
    if (action == "filter") {
        if (match($0, re[target])) {
            unique[extract($0, target)] = ""
        }
    } else if (action == "tasks") {
        if (match($0, RE_MODULE)) {
            if (output_tasks) {
                print ""
                print output_module
                print output_tasks
                output_tasks = ""
            }
            doc = ""
            match_task = 0
            output_module = ". " extract($0, "module")
        } else if (match($0, RE_TASK)) {
            if (target) {
                if (target == extract($0, "task")) {
                    match_task = 1
                }
            } else {
                match_task = 1
            }
            append($0)
        } else if (match($0, RE_COMMENT)) {
            append($0)
        } else {
            if (match_task) {
                output_tasks = output_tasks "\n" doc
            }
            doc = ""
            match_task = 0
        }
    } else if (action == "eval") {
        if (match($0, re[target])) {
            append(extract($0, target))
        } else if (match($0, re["function"])) {
            split(doc, array, "\n")
            for (item in array) {
                alias_eval(array[item], extract($0, "function"), "function")
            }
            reset()
        } else {
            reset()
        }
    } else if (action == "function") {
        if (match($0, re["command"])) {
            append(extract($0, "command"))
        } else if (match($0, re["function"])) {
            split(doc, array, "\n")
            for (item in array) {
                if (array[item] == target) {
                    print extract($0, "function")
                    exit
                }
            }
            reset()
        } else {
            reset()
        }
    } else if (action == "doc") {
        # doc
        if (match($0, RE_SHEBANG)) {
            append("! " extract($0, "shebang"))
        } else if (match($0, RE_DOC)) {
            if (f) {
                append($0)
            } else {
                append(extract($0, "doc"))
            }
        } else if (match($0, re["alias"])) {
            matched = extract($0, "alias")
            append("= " matched)
            if (matched == target) {
                match_alias = 1
            }
        } else if (match($0, re["command"])) {
            matched = extract($0, "command")
            append("/ " matched)
            if (matched == target) {
                match_command = 1
            }
        # set
        } else if (match($0, re["constant"])) {
            matched = extract($0, "constant")
            if (matched == target) {
                output(matched, "constant")
            } else {
                reset()
            }
        } else if (match($0, re["variable"])) {
            matched = extract($0, "variable")
            if (matched == target) {
                output(matched, "variable")
            } else {
                reset()
            }
        # others
        } else if (match($0, RE_MODULE, m)) {
            reset()
            if (m[1] == target) {
                match_module = 1
            }
        } else if (match($0, re["function"], m)) {
            f = m[1]
        } else if (match($0, RE_CLOSE, m)) {
            if (match_alias) {
                print "= " target
                output(f, "function")
            } else if (match_command) {
                print "/ " target
                output(f, "function")
            } else if (f == target) {
                output(f, "function")
            } else {
                f = ""
                reset()
            }
        } else {
            if (match_module) {
                output(target, "module")
            } else {
                reset()
            }
        }
    }
}

END {
    if (action == "filter") {
        for (item in unique) {
            print item
        }
    }
}