import {
    fill, range, limit
} from "../../core/iterable.ts"

import { assertEquals, assert } from "https://deno.land/std@0.140.0/testing/asserts.ts"

Deno.test("fill, yield the same value every time", () => {
    const count = 50_000
    const item = "hi"
    let i = 0
    for (const el of fill(item, count)) {
        assertEquals(el, item)
        i++
    }
    assertEquals(i, count)
})


Deno.test("range: one arg", () => {
    const iter = range(50_000)
    for (let i = 0; i < 50_000; i++) {
        const next = iter.next()
        assertEquals(next.value, i)
    }
    assert(iter.next().done)
})

Deno.test("range: two args, positive", () => {
    const iter = range(40, 50)
    for (let i = 40; i < 50; i++) {
        const next = iter.next()
        assertEquals(next.value, i)
    }
    assert(iter.next().done)
})

Deno.test("range: two args, negative", () => {
    const iter = range(50, 40)
    for (let i = 50; i > 40; i--) {
        const next = iter.next()
        assertEquals(next.value, i)
    }
    assert(iter.next().done)
})

Deno.test("range: three args, positive", () => {
    const iter = range(60, 80, 4)
    for (let i = 60; i < 80; i += 4) {
        const next = iter.next()
        assertEquals(next.value, i)
    }
    assert(iter.next().done)
})

Deno.test("range: three args, negative", () => {
    const iter = range(80, 60, 4)
    for (let i = 80; i > 60; i -= 4) {
        const next = iter.next()
        assertEquals(next.value, i)
    }
    assert(iter.next().done)
})

Deno.test("limit: limits to the first n elements", () => {
    const values: number[] = []
    const truth = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181]
    const count = truth.length
    for (const value of limit(count, fibonacci())) {
        values.push(value)
    }
    assertEquals(values.length, count)
    truth.forEach((val, i) => {
        assertEquals(values[i], val)
    })
})

function* fibonacci() {
    let back2 = 0
    let back1 = 1
    yield back2
    yield back1
    while (true) {
        const sum = back2 + back1
        back2 = back1
        back1 = sum
        yield sum
    }
}