// ============================================================================
// Slugify — turn a title into a URL-safe slug
// ============================================================================
//
// Lowercases, keeps alphanumerics, turns every run of other characters into a
// single hyphen, and trims leading/trailing hyphens. Demonstrates a per-char
// accumulator with a "last was separator" flag to collapse runs.
//
// Run: soma run slugify.cell --signal slugify "Hello, World!  Foo--Bar"

cell Slugify {
    face {
        signal slugify(title: String) -> String
    }

    on slugify(title: String) {
        let low = lowercase(title)
        let out = ""
        let pending_dash = false
        for i in range(0, len(low)) {
            let c = low[i]
            if (c >= "a" && c <= "z") || (c >= "0" && c <= "9") {
                if pending_dash && len(out) > 0 {
                    out = out + "-"
                }
                pending_dash = false
                out = out + c
            } else {
                pending_dash = true
            }
        }
        return out
    }
}

cell test SlugifyTest {
    rules {
        assert slugify("Hello World") == "hello-world"
        assert slugify("Hello, World!") == "hello-world"
        assert slugify("  Foo --  Bar  ") == "foo-bar"
        assert slugify("Already-Slug-99") == "already-slug-99"
        assert slugify("!!!") == ""
    }
}