// edge.el — Edge type definitions and visual encoding.
//
// Edges are directed (source -> target) with a weight and optional relation label.

// ── Edge JSON accessors ──────────────────────────────────────────────────────
//
// Edges are passed as JSON objects: { source_id, target_id, weight, relation }

fn edge_source(e_json: String) -> String {
    let s: String = json_get_string(e_json, "source_id")
    if !str_eq(s, "") { return s }
    json_get_string(e_json, "source")
}

fn edge_target(e_json: String) -> String {
    let t: String = json_get_string(e_json, "target_id")
    if !str_eq(t, "") { return t }
    json_get_string(e_json, "target")
}

fn edge_weight(e_json: String) -> Float {
    let w: Float = json_get_float(e_json, "weight")
    if w == int_to_float(0) { return int_to_float(1) }
    w
}

fn edge_relation(e_json: String) -> String {
    json_get_string(e_json, "relation")
}

// ── Edge visual encoding ─────────────────────────────────────────────────────

// Stroke width clamped to [1, 4] based on weight.
fn edge_stroke_width(weight: Float) -> Float {
    let min_w: Float = int_to_float(1)
    let max_w: Float = int_to_float(4)
    let range: Float = max_w - min_w
    let clamped: Float = if weight < min_w { min_w } else { if weight > max_w { max_w } else { weight } }
    clamped
}

fn edge_stroke_color() -> String { "#3a4a5a" }

fn edge_stroke_color_highlight() -> String { "#5a7a9a" }