mm <- function(...) {
  v <- as.numeric(as.vector(list(...)))
  matrix(v, nrow = sqrt(length(v)))
}
am <- function(x) {
  x <- as.matrix(x)
  dimnames(x) <- NULL
  x
}

g <- make_tree(20)

test_that("[ indexing works", {
  ## Are these vertices connected?
  expect_that(g[1, 2], equals(1))
  expect_that(am(g[c(1, 1, 7), c(2, 3, 14)]), equals(mm(1, 1, 0, 1, 1, 0, 0, 0, 1)))
  expect_that(am(g[c(1, 1, 7), c(5, 3, 12)]), equals(mm(0, 0, 0, 1, 1, 0, 0, 0, 0)))
  expect_that(am(g[c(1, 1, 1, 1), c(2, 3, 2, 2)]), equals(matrix(1, 4, 4)))
  expect_that(am(g[c(8, 17), c(17, 8)]), equals(mm(1, 0, 0, 0)))
})

V(g)$name <- letters[1:vcount(g)]

test_that("[ indexing works with symbolic names", {
  ## The same with symbolic names
  expect_that(g["a", "b"], equals(1))
  expect_that(
    am(g[c("a", "a", "g"), c("b", "c", "n")]),
    equals(mm(1, 1, 0, 1, 1, 0, 0, 0, 1))
  )
  expect_that(
    am(g[c("a", "a", "g"), c("e", "c", "l")]),
    equals(mm(0, 0, 0, 1, 1, 0, 0, 0, 0))
  )
  expect_that(
    am(g[c("a", "a", "a", "a"), c("b", "c", "b", "b")]),
    equals(matrix(1, 4, 4))
  )
  expect_that(am(g[c("h", "q"), c("q", "h")]), equals(mm(1, 0, 0, 0)))
})

test_that("[ indexing works with logical vectors", {
  ## Logical vectors
  lres <- structure(
    c(
      0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0
    ),
    .Dim = c(2L, 20L),
    .Dimnames = list(c("b", "c"), c(
      "a", "b", "c",
      "d", "e", "f", "g", "h", "i", "j", "k", "l",
      "m", "n", "o", "p", "q", "r", "s", "t"
    ))
  )
  expect_that(g[degree(g, mode = "in") == 0, 2], equals(1))
  expect_that(as.matrix(g[2:3, TRUE]), equals(lres))
})

test_that("[ indexing works with negative indices", {
  ## Negative indices
  nres <- structure(
    c(
      0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0
    ),
    .Dim = c(2L, 19L),
    .Dimnames = list(
      c("b", "c"),
      c(
        "b", "c", "d", "e", "f", "g", "h", "i", "j",
        "k", "l", "m", "n", "o", "p", "q", "r", "s",
        "t"
      )
    )
  )
  expect_that(as.matrix(g[2:3, -1]), equals(nres))
})

el <- as_edgelist(g, names = FALSE)
E(g)$weight <- el[, 1] * el[, 2]

test_that("[ indexing works with weighted graphs", {
  ## Weighted graphs
  expect_that(g[1, 2], equals(2))
  expect_that(am(g[c(1, 1, 7), c(2, 3, 14)]), equals(mm(2, 2, 0, 3, 3, 0, 0, 0, 98)))
  expect_that(am(g[c(1, 1, 7), c(5, 3, 12)]), equals(mm(0, 0, 0, 3, 3, 0, 0, 0, 0)))
  expect_that(
    am(g[c(1, 1, 1, 1), c(2, 3, 2, 2)]),
    equals(mm(2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2))
  )
  expect_that(am(g[c(8, 17), c(17, 8)]), equals(mm(136, 0, 0, 0)))
})

test_that("[ indexing works with weighted graphs and symbolic names", {
  ## Weighted graph, with symbolic names
  expect_that(g["a", "b"], equals(2))
  expect_that(
    am(g[c("a", "a", "g"), c("b", "c", "n")]),
    equals(mm(2, 2, 0, 3, 3, 0, 0, 0, 98))
  )
  expect_that(
    am(g[c("a", "a", "g"), c("e", "c", "l")]),
    equals(mm(0, 0, 0, 3, 3, 0, 0, 0, 0))
  )
  expect_that(
    am(g[c("a", "a", "a", "a"), c("b", "c", "b", "b")]),
    equals(mm(2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2))
  )
  expect_that(am(g[c("h", "q"), c("q", "h")]), equals(mm(136, 0, 0, 0)))
})

################################################################

test_that("[[ indexing works", {
  ## Adjacent vertices
  expect_that(g[[1, ]], is_equivalent_to(list(a = V(g)[2:3])))
  expect_that(g[[, 2]], is_equivalent_to(list(b = V(g)[1])))
  expect_that(
    g[[, 2, directed = FALSE]],
    is_equivalent_to(list(b = V(g)[c(1, 4, 5)]))
  )
  expect_that(
    g[[2, directed = FALSE]],
    is_equivalent_to(list(b = V(g)[c(1, 4, 5)]))
  )

  expect_that(g[[1:3, ]], is_equivalent_to(list(
    a = V(g)[2:3], b = V(g)[4:5],
    c = V(g)[6:7]
  )))
  expect_that(g[[, 1:3]], is_equivalent_to(list(
    a = V(g)[numeric()],
    b = V(g)[1], c = V(g)[1]
  )))
})

test_that("[[ indexing works with symbolic names", {
  ## Same with vertex names
  expect_that(g[["a", ]], is_equivalent_to(list(a = V(g)[2:3])))
  expect_that(g[[, "b"]], is_equivalent_to(list(b = V(g)[1])))
  expect_that(
    g[[, "b", directed = FALSE]],
    is_equivalent_to(list(b = V(g)[c(1, 4, 5)]))
  )
  expect_that(
    g[["b", directed = FALSE]],
    is_equivalent_to(list(b = V(g)[c(1, 4, 5)]))
  )

  expect_that(
    g[[letters[1:3], ]],
    is_equivalent_to(list(a = V(g)[2:3], b = V(g)[4:5], c = V(g)[6:7]))
  )
  expect_that(
    g[[, letters[1:3]]],
    is_equivalent_to(list(a = V(g)[numeric()], b = V(g)[1], c = V(g)[1]))
  )
})

test_that("[[ indexing works with logical vectors", {
  ## Logical vectors
  expect_that(
    g[[degree(g, mode = "in") == 0, ]],
    is_equivalent_to(list(a = V(g)[2:3]))
  )
})

test_that("[[ indexing works with filtering on both ends", {
  ## Filtering on both ends
  expect_that(
    g[[1:10, 1:10]],
    is_equivalent_to(list(
      a = V(g)[2:3], b = V(g)[4:5], c = V(g)[6:7], d = V(g)[8:9],
      e = V(g)[10], f = V(g)[numeric()], g = V(g)[numeric()], h = V(g)[numeric()],
      i = V(g)[numeric()], j = V(g)[numeric()]
    ))
  )
})

test_that("[[ indexing is consistent with length()", {
  expect_that(length(g), equals(vcount(g)))
})

################################################################

test_that("[ can query edge ids", {
  ## Query edge ids
  expect_that(g[1, 2, edges = TRUE], equals(1))
  expect_that(
    am(g[c(1, 1, 7), c(2, 3, 14), edges = TRUE]),
    equals(mm(1, 1, 0, 2, 2, 0, 0, 0, 13))
  )
  expect_that(
    am(g[c(1, 1, 7), c(5, 3, 12), edges = TRUE]),
    equals(mm(0, 0, 0, 2, 2, 0, 0, 0, 0))
  )
  expect_that(
    am(g[c(1, 1, 1, 1), c(2, 3, 2, 2), edges = TRUE]),
    equals(mm(1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1))
  )
  expect_that(
    am(g[c(8, 17), c(17, 8), edges = TRUE]),
    equals(mm(16, 0, 0, 0))
  )
})

test_that("[ can query edge ids with symbolic names", {
  ## The same with symbolic names
  expect_that(g["a", "b", edges = TRUE], equals(1))
  expect_that(
    am(g[c("a", "a", "g"), c("b", "c", "n"), edges = TRUE]),
    equals(mm(1, 1, 0, 2, 2, 0, 0, 0, 13))
  )
  expect_that(
    am(g[c("a", "a", "g"), c("e", "c", "l"), edges = TRUE]),
    equals(mm(0, 0, 0, 2, 2, 0, 0, 0, 0))
  )
  expect_that(
    am(g[c("a", "a", "a", "a"), c("b", "c", "b", "b"), edges = TRUE]),
    equals(mm(1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1))
  )
  expect_that(
    am(g[c("h", "q"), c("q", "h"), edges = TRUE]),
    equals(mm(16, 0, 0, 0))
  )
})

################################################################

test_that("[[ can query incident edges", {
  ## Incident edges of vertices
  expect_that(g[[1, , edges = TRUE]], is_equivalent_to(list(a = E(g)[1:2])))
  expect_that(g[[, 2, edges = TRUE]], is_equivalent_to(list(b = E(g)[1])))
  expect_that(
    g[[, 2, directed = FALSE, edges = TRUE]],
    is_equivalent_to(list(b = E(g)[c(1, 3, 4)]))
  )
  expect_that(
    g[[2, directed = FALSE, edges = TRUE]],
    is_equivalent_to(list(b = E(g)[c(1, 3, 4)]))
  )

  expect_that(
    g[[1:3, , edges = TRUE]],
    is_equivalent_to(list(a = E(g)[1:2], b = E(g)[3:4], c = E(g)[5:6]))
  )
  expect_that(
    g[[, 1:3, edges = TRUE]],
    is_equivalent_to(list(a = E(g)[numeric()], b = E(g)[1], c = E(g)[2]))
  )
})

test_that("[[ queries edges with vertex names", {
  ## Same with vertex names
  expect_that(
    g[["a", , edges = TRUE]],
    is_equivalent_to(list(a = E(g)[1:2]))
  )
  expect_that(
    g[[, "b", edges = TRUE]],
    is_equivalent_to(list(b = E(g)[1]))
  )
  expect_that(
    g[[, "b", directed = FALSE, edges = TRUE]],
    is_equivalent_to(list(b = E(g)[c(1, 3, 4)]))
  )
  expect_that(
    g[["b", directed = FALSE, edges = TRUE]],
    is_equivalent_to(list(b = E(g)[c(1, 3, 4)]))
  )

  expect_that(
    g[[letters[1:3], , edges = TRUE]],
    is_equivalent_to(list(a = E(g)[1:2], b = E(g)[3:4], c = E(g)[5:6]))
  )
  expect_that(
    g[[, letters[1:3], edges = TRUE]],
    is_equivalent_to(list(a = E(g)[numeric()], b = E(g)[1], c = E(g)[2]))
  )

  ## Filtering on both ends
  expect_that(
    g[[1:10, 1:10, edges = TRUE]],
    is_equivalent_to(list(
      E(g)[1:2], E(g)[3:4], E(g)[5:6], E(g)[7:8],
      E(g)[9], E(g)[numeric()], E(g)[numeric()],
      E(g)[numeric()], E(g)[numeric()], E(g)[numeric()]
    ))
  )
})

#################################################################

test_that("[ handles from and to properly", {
  ## from & to
  g <- make_tree(20)
  expect_that(g[from = c(1, 2, 2, 3), to = c(3, 4, 8, 7)], equals(c(1, 1, 0, 1)))

  V(g)$name <- letters[1:20]
  expect_that(
    g[from = c("a", "b", "b", "c"), to = c("c", "d", "h", "g")],
    equals(c(1, 1, 0, 1))
  )

  E(g)$weight <- (1:ecount(g))^2
  expect_that(
    g[from = c("a", "b", "b", "c"), to = c("c", "d", "h", "g")],
    equals(c(4, 9, 0, 36))
  )

  expect_that(g[
    from = c("a", "b", "b", "c"), to = c("c", "d", "h", "g"),
    edges = TRUE
  ], equals(c(2, 3, 0, 6)))
})

test_that("[[ works with from and to", {
  g <- make_tree(20)

  expect_equal(ignore_attr = TRUE, g[[1, ]], g[[from = 1]])
  expect_equal(ignore_attr = TRUE, g[[, 1]], g[[to = 1]])
  expect_equal(ignore_attr = TRUE, g[[1:5, 4:10]], g[[from = 1:5, to = 4:10]])

  expect_error(g[[1, from = 1]], "Cannot give both")
  expect_error(g[[, 2, to = 10]], "Cannot give both")
})

test_that("[[ returns vertex and edges sequences", {
  g <- make_tree(20)
  expect_true(is_igraph_vs(g[[1]][[1]]))
  expect_true(is_igraph_es(g[[1, edges = TRUE]][[1]]))
  expect_true(is_igraph_vs(g[[1:3, 2:6]][[1]]))
  expect_true(is_igraph_es(g[[1:3, 2:6, edges = TRUE]][[1]]))
})

test_that("[[ handles from and to properly even if the graph has conflicting vertex attributes", {
  ## from & to
  g <- make_tree(20)
  V(g)$i <- 200:219
  V(g)$j <- 200:219
  expect_true(is_igraph_vs(g[[1:3, 2:6]][[1]]))
  expect_true(is_igraph_vs(g[[from = 1:3, to = 2:6]][[1]]))
})