import "def.gem"
import "mem.gem"

type box: Vec {
    type gen: T

    silent ref T: buf
    silent u32: cap = 0
    silent u32: len = 0

    silent fun refit(in u32: ext) {
        if self.cap == 0 {
            self.cap = ext
            heap_alloc(self.cap * sizeof(T), self.buf)
        } else if self.len == self.cap || self.cap - self.len - ext < 0 {
            # reallocate buffer
            self.cap = self.cap + ext

            heap_realloc(self.cap * sizeof(T), self.buf)
        }
        # TODO: shrink if cap - len > ext
    }

    fun append(in T: t) {
        self.refit(1)

        self.buf[self.len] = t
        self.len = self.len + 1
    } 

    fun prepend(in T: t) {
        self.refit(1)

        u32 i = self.len
        while i > 0 {
            self.buf[i] = self.buf[i - 1]
            i = i - 1
        }

        self.buf[0] = t
    }

    fun remove(in u32: idx)(out T: t) {
        t = self.buf[idx]

        u32 i = idx
        while i < self.len - 1 {
            self.buf[i] = self.buf[i + 1]
            i = i + 1
        }

        self.len = self.len - 1

        self.refit(1)
    }

    fun get(in u32: idx)(out T: t) {
        t = self.buf[idx]
    }

    fun len(out u32: len) {
        len = self.len
    }

    fun append_vec(in ref Vec of T: other) {
        u32: len_other
        other.len(len_other)

        self.refit(len_other)

        u32: idx = 0
        while idx < len_other {
            other.get(self.buf[self.len])
            self.len = self.len + 1
            idx = idx + 1
        }
    }
}