module maps

// filter filters map entries by the given predicate function
pub fn filter[K, V](m map[K]V, f fn (key K, val V) bool) map[K]V {
    mut mp := map[K]V{}

    for k, v in m {
        $if V is $interface {
            if f(k, unsafe { v }) {
                mp[k] = v
            }
        } $else {
            if f(k, v) {
                mp[k] = v
            }
        }
    }

    return mp
}

// to_array maps map entries into one-dimensional array
pub fn to_array[K, V, I](m map[K]V, f fn (key K, val V) I) []I {
    mut a := []I{cap: m.len}

    for k, v in m {
        $if V is $interface {
            a << f(k, unsafe { v })
        } $else {
            a << f(k, v)
        }
    }

    return a
}

// flat_map maps map entries into arrays and flattens into a one-dimensional array
pub fn flat_map[K, V, I](m map[K]V, f fn (key K, val V) []I) []I {
    mut a := []I{cap: m.len}

    for k, v in m {
        $if V is $interface {
            a << f(k, unsafe { v })
        } $else {
            a << f(k, v)
        }
    }

    return a
}

// to_map maps map entries into new entries and constructs a new map
pub fn to_map[K, V, X, Y](m map[K]V, f fn (key K, val V) (X, Y)) map[X]Y {
    mut mp := map[X]Y{}

    for k, v in m {
        $if V is $interface {
            x, y := f(k, unsafe { v })
            mp[x] = y
        } $else {
            x, y := f(k, v)
            mp[x] = y
        }
    }

    return mp
}

// invert returns a new map, created by swapping key to value and vice versa for each entry.
pub fn invert[K, V](m map[K]V) map[V]K {
    mut mp := map[V]K{}

    for k, v in m {
        mp[v] = k
    }

    return mp
}

// from_array maps array into map with index to element per entry
pub fn from_array[T](array []T) map[int]T {
    mut mp := map[int]T{}

    for i, e in array {
        mp[i] = e
    }

    return mp
}

// merge_in_place merges all elements of `m2` into the mutable map `m1`.
// If a key exists in both maps, the value from `m1` will be overwritten by the
// value from `m2`.
// Note that this function modifes `m1`, while `m2` will not be.
pub fn merge_in_place[K, V](mut m1 map[K]V, m2 map[K]V) {
    for k, v in m2 {
        $if v is $map {
            m1[k] = v.clone()
        } $else {
            m1[k] = v
        }
    }
}

// merge produces a map, that is the result of merging the first map `m1`,
// with the second map `m2`. If a key exists in both maps, the value from m2,
// will override the value from m1.
// The original maps `m1` and `m2`, will not be modified. The return value is a new map.
pub fn merge[K, V](m1 map[K]V, m2 map[K]V) map[K]V {
    mut res := m1.clone()
    for k, v in m2 {
        $if v is $map {
            res[k] = v.clone()
        } $else {
            res[k] = v
        }
    }
    return res
}