// Counts the words in a file: maps, methods and errors as values.
//   finch run examples/wordcount.fch README.md

struct Counter {
    map[str]int counts
    int total
}

// lower-case letters and digits only: "Hello," -> "hello"
fn clean(str word) -> str {
    out := ""
    for c in word.lower() {
        if (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') {
            out += str(c)
        }
    }
    return out
}

fn Counter.add(str text) {
    for word in text.split(" ") {
        w := clean(word)
        if w.len > 0 {
            self.counts[w] += 1        // a new word starts at 0
            self.total += 1
        }
    }
}

// the n most frequent words, most frequent first
fn Counter.top(int n) -> []str {
    words := self.counts.keys()
    for i in 0..words.len {
        for j in i + 1..words.len {
            if self.counts[words[j]] > self.counts[words[i]] {
                w := words[i]
                words[i] = words[j]
                words[j] = w
            }
        }
    }
    if words.len > n {
        words.resize(n)
    }
    return words
}

fn main([]str args) -> ! {
    if args.len < 2 {
        return error("usage: wordcount <file>")
    }
    text := try read_file(args[1])     // a missing file ends the program with a clear message

    Counter c
    for line in text.split("\n") {
        c.add(line)
    }
    print(c.total, "words,", c.counts.len, "different")
    for i, w in c.top(10) {
        print(i + 1, w, c.counts[w])
    }
}