#!/bin/bash
# extract-core.sh — Extract Tiny Core Linux rootfs from ISO
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
PROJECT_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
CACHE_DIR="${CACHE_DIR:-$PROJECT_ROOT/build/cache}"
ROOTFS_DIR="${ROOTFS_DIR:-$PROJECT_ROOT/build/rootfs-work}"

# shellcheck source=../config/versions.env
. "$SCRIPT_DIR/../config/versions.env"

EXTRACT_ARCH="${TARGET_ARCH:-amd64}"

# Clean previous rootfs
rm -rf "$ROOTFS_DIR"
mkdir -p "$ROOTFS_DIR"

# =========================================================================
# ARM64: piCore64 .img.gz extraction (SD card image, not ISO)
# =========================================================================
if [ "$EXTRACT_ARCH" = "arm64" ]; then
    PICORE_IMG="$CACHE_DIR/$PICORE_IMAGE"
    if [ ! -f "$PICORE_IMG" ]; then
        echo "ERROR: piCore64 image not found: $PICORE_IMG"
        echo "Run 'TARGET_ARCH=arm64 make fetch' first."
        exit 1
    fi

    echo "==> Extracting piCore64 image: $PICORE_IMG"

    # Decompress .img.gz to raw image
    PICORE_RAW="$CACHE_DIR/piCore-${PICORE_VERSION}.img"
    if [ ! -f "$PICORE_RAW" ]; then
        echo "    Decompressing..."
        gunzip -k "$PICORE_IMG" 2>/dev/null || \
            zcat "$PICORE_IMG" > "$PICORE_RAW"
    fi

    # Mount the piCore rootfs partition (partition 2 in the SD image)
    # Use losetup to find the partition offset
    IMG_MNT=$(mktemp -d)
    echo "    Mounting piCore rootfs partition..."

    # Get partition 2 offset (piCore layout: boot=p1, rootfs=p2)
    OFFSET=$(fdisk -l "$PICORE_RAW" 2>/dev/null | awk '/^.*img2/{print $2}')
    if [ -z "$OFFSET" ]; then
        # Fallback: try sfdisk
        OFFSET=$(sfdisk -d "$PICORE_RAW" 2>/dev/null | awk -F'[=,]' '/start=/{print $2; exit}' | tr -d ' ')
    fi
    if [ -z "$OFFSET" ]; then
        echo "ERROR: Could not determine partition offset in piCore image"
        fdisk -l "$PICORE_RAW" || true
        exit 1
    fi

    BYTE_OFFSET=$((OFFSET * 512))
    mount -o loop,ro,offset="$BYTE_OFFSET" "$PICORE_RAW" "$IMG_MNT" || {
        echo "ERROR: Failed to mount piCore rootfs (need root for losetup)"
        exit 1
    }

    # Find initramfs in the piCore rootfs
    COREGZ=""
    for f in "$IMG_MNT"/boot/corepure64.gz "$IMG_MNT"/boot/core.gz "$IMG_MNT"/*.gz; do
        [ -f "$f" ] && COREGZ="$f" && break
    done

    if [ -z "$COREGZ" ]; then
        echo "ERROR: Could not find initramfs in piCore image"
        echo "Contents:"
        ls -la "$IMG_MNT"/
        ls -la "$IMG_MNT"/boot/ 2>/dev/null || true
        umount "$IMG_MNT" 2>/dev/null || true
        exit 1
    fi

    echo "==> Found initramfs: $COREGZ"

    # Extract initramfs
    mkdir -p "$ROOTFS_DIR/rootfs"
    cd "$ROOTFS_DIR/rootfs"
    zcat "$COREGZ" | cpio -idm 2>/dev/null

    # Note: ARM64 kernel comes from build-kernel-arm64.sh, not from piCore
    # We only use piCore for the BusyBox userland

    cd "$PROJECT_ROOT"
    umount "$IMG_MNT" 2>/dev/null || true
    rm -rf "$IMG_MNT"

    echo "==> ARM64 rootfs extracted: $ROOTFS_DIR/rootfs"
    echo "    Size: $(du -sh "$ROOTFS_DIR/rootfs" | cut -f1)"
    echo "==> Extract complete (ARM64). Kernel will come from build-kernel-arm64.sh"
    exit 0
fi

# =========================================================================
# x86_64: Tiny Core ISO extraction
# =========================================================================
TC_ISO="$CACHE_DIR/$TINYCORE_ISO"
ISO_MNT="$ROOTFS_DIR/iso-mount"

if [ ! -f "$TC_ISO" ]; then
    echo "ERROR: Tiny Core ISO not found: $TC_ISO"
    echo "Run 'make fetch' first."
    exit 1
fi

mkdir -p "$ISO_MNT"

# --- Mount ISO and extract kernel + initramfs ---
echo "==> Mounting ISO: $TC_ISO"
mount -o loop,ro "$TC_ISO" "$ISO_MNT" 2>/dev/null || {
    # Fallback for non-root: use 7z or bsdtar
    echo "    mount failed (need root?), trying bsdtar..."
    mkdir -p "$ISO_MNT"
    bsdtar xf "$TC_ISO" -C "$ISO_MNT" 2>/dev/null || {
        echo "    bsdtar failed, trying 7z..."
        7z x -o"$ISO_MNT" "$TC_ISO" >/dev/null 2>&1
    }
}

# Find vmlinuz and core.gz (path varies by Tiny Core version/arch)
VMLINUZ=""
COREGZ=""
for f in "$ISO_MNT"/boot/vmlinuz64 "$ISO_MNT"/boot/vmlinuz; do
    [ -f "$f" ] && VMLINUZ="$f" && break
done
for f in "$ISO_MNT"/boot/corepure64.gz "$ISO_MNT"/boot/core.gz; do
    [ -f "$f" ] && COREGZ="$f" && break
done

if [ -z "$VMLINUZ" ] || [ -z "$COREGZ" ]; then
    echo "ERROR: Could not find vmlinuz/core.gz in ISO"
    echo "ISO contents:"
    find "$ISO_MNT" -type f
    umount "$ISO_MNT" 2>/dev/null || true
    exit 1
fi

echo "==> Found kernel: $VMLINUZ"
echo "==> Found initramfs: $COREGZ"

# Copy kernel
cp "$VMLINUZ" "$ROOTFS_DIR/vmlinuz"

# --- Extract initramfs (core.gz → rootfs) ---
echo "==> Extracting initramfs..."
mkdir -p "$ROOTFS_DIR/rootfs"
cd "$ROOTFS_DIR/rootfs"
zcat "$COREGZ" | cpio -idm 2>/dev/null

# Unmount ISO
cd "$PROJECT_ROOT"
umount "$ISO_MNT" 2>/dev/null || true
rm -rf "$ISO_MNT"

echo "==> Rootfs extracted: $ROOTFS_DIR/rootfs"
echo "    Size: $(du -sh "$ROOTFS_DIR/rootfs" | cut -f1)"
echo "    Kernel: $ROOTFS_DIR/vmlinuz ($(du -h "$ROOTFS_DIR/vmlinuz" | cut -f1))"

# --- Audit kernel config if available ---
if [ -f "$ROOTFS_DIR/rootfs/proc/config.gz" ]; then
    echo "==> Kernel config found in rootfs, auditing..."
    "$SCRIPT_DIR/../config/kernel-audit.sh" <(zcat "$ROOTFS_DIR/rootfs/proc/config.gz") || true
fi

echo "==> Extract complete."