# The graph of research 118 (docs/design/018 stage 2): edges keyed by
# from * 1048576 + to, loaded in bulk as rows; a breadth first search in
# one event, its queue and what it has seen the event's own lists.
record Edge {
  link = 0
  to = 0
}
record Seen {
  node = 0
  depth = 0
}
record Step {
  node = 0
}
state edges: list of Edge by link
state nodes = 0
state hops = -1
state reached = 0
state sum = 0
input size = message {
  nodes: u32
}
input load = message {
  rows: list of Edge
}
input frontier = message {
  from: u32
  to: u32
}
input route = message {
  from: u32
  to: u32
}
on size {
  nodes = size.nodes
}
on load {
  for r in load.rows {
    edges.add(Edge { ..r })
  }
}
on route {
  let seen: list of Seen by node
  let queue: list of Step
  queue.append(Step { node: route.from })
  seen.add(Seen { node: route.from })
  for i in 0 .. nodes {
    if i >= queue.count { break }
    let q = queue.first + i
    for e in edges[q.node * 1048576 .. q.node * 1048576 + 1048576] {
      if !seen.has(e.to) {
        seen.add(Seen { node: e.to, depth: seen[q.node].depth + 1 })
        queue.append(Step { node: e.to })
      }
    }
  }
  hops = if seen.has(route.to) { seen[route.to].depth } else { -1 }
  reached = seen.count
}
view far = hops
view found = reached

on frontier {
  let queue: list of Step
  for v in 0 .. nodes {
    queue.append(Step { node: v })
  }
  let total = 0
  for i in 0 .. nodes {
    if i >= queue.count { break }
    let q = queue.first + i
    for e in edges[q.node * 1048576 .. q.node * 1048576 + 1048576] {
      total = total + e.to
    }
  }
  sum = total
}