#!/bin/bash

# Resolving where a snapshot's data actually lives, and where it should land.
#
# The bug this exists to fix predates storage locations. Restore did:
#
#     engineRestoreSnapshot "$idx" "$id" "/" "$containers_dir$app"
#
# — restore to / with an include filter built from the LOCAL containers root.
# restic reproduces a snapshot's absolute paths, so that only works when source
# and destination paths are byte-identical. LibrePortal has shipped three
# configurable roots for a while, so migrating from a host installed with
# --containers-dir=/mnt/ssd/apps onto a default host matched no include path and
# restored NOTHING, silently. Storage locations make that ordinary rather than
# rare.
#
# The fix is to take the source path from the SNAPSHOT rather than from local
# config, and to stage-and-move whenever it differs from where the app belongs
# here.

# The path an app occupied in a snapshot. restic records the backed-up paths on
# the snapshot itself, so ask the repository rather than guessing.
storageSnapshotSourcePath()
{
    local idx="$1" snapshot_id="$2" app="$3"
    local json path

    json=$(engineSnapshotsJson "$idx" "$snapshot_id" 2>/dev/null) || return 1
    # "paths":["/libreportal-containers/bookstack"]
    path=$(printf '%s' "$json" \
        | grep -o '"paths":\[[^]]*\]' \
        | head -1 \
        | grep -o '"/[^"]*"' \
        | tr -d '"' \
        | grep -E "/${app}(/|$)" \
        | head -1)
    [[ -n "$path" ]] || return 1
    printf '%s' "${path%/}"
}

# Restore an app from a snapshot to wherever it belongs on THIS host.
#
# Same path on both sides -> restore in place, exactly as before.
# Different -> restore into staging, then move the tree into position. The move
# goes through the root helper because the restored tree carries container
# sub-UIDs the manager cannot handle.
storageRestoreAppTo()
{
    local idx="$1" snapshot_id="$2" app="$3"

    local dest
    if ! dest=$(appDir "$app"); then
        isError "Cannot restore $app — its storage location is not mounted."
        return 1
    fi

    local src
    if ! src=$(storageSnapshotSourcePath "$idx" "$snapshot_id" "$app"); then
        # Older snapshot, or an engine that does not report paths: fall back to
        # the historical behaviour rather than refusing.
        isNotice "Snapshot does not report its source path — restoring in place."
        engineRestoreSnapshot "$idx" "$snapshot_id" "/" "$dest"
        return $?
    fi

    if [[ "${src%/}" == "${dest%/}" ]]; then
        engineRestoreSnapshot "$idx" "$snapshot_id" "/" "$src"
        return $?
    fi

    isNotice "This snapshot was taken at '$src'; restoring to '$dest'."

    local stage="${restore_dir%/}/relocate-$app.$$"
    runInstallOp mkdir -p "$stage"
    if ! engineRestoreSnapshot "$idx" "$snapshot_id" "$stage" "$src"; then
        isError "Restore into staging failed."
        runInstallOp rm -rf "$stage"
        return 1
    fi

    # restic reproduces the full absolute path beneath --target.
    local staged="$stage/${src#/}"
    if [[ ! -d "$staged" ]]; then
        isError "Restored tree not found at '$staged' — leaving staging in place for inspection."
        return 1
    fi

    if ! runOwnership app-adopt "$app" "$staged" "${dest%/*}"; then
        isError "Could not move the restored tree into '$dest' — it is still at '$staged'."
        return 1
    fi

    runInstallOp rm -rf "$stage"
    isSuccessful "Restored $app to $dest"
    return 0
}