// SPDX-License-Identifier: GPL-2.0
/*
 * C++ stream style string builder used in KUnit for building messages.
 *
 * Copyright (C) 2019, Google LLC.
 * Author: Brendan Higgins <brendanhiggins@google.com>
 */

#include <kunit/test.h>
#include <linux/list.h>
#include <linux/slab.h>

#include "string-stream.h"

struct string_stream_fragment_alloc_context {
        struct kunit *test;
        int len;
        gfp_t gfp;
};

static int string_stream_fragment_init(struct kunit_resource *res,
                                       void *context)
{
        struct string_stream_fragment_alloc_context *ctx = context;
        struct string_stream_fragment *frag;

        frag = kunit_kzalloc(ctx->test, sizeof(*frag), ctx->gfp);
        if (!frag)
                return -ENOMEM;

        frag->test = ctx->test;
        frag->fragment = kunit_kmalloc(ctx->test, ctx->len, ctx->gfp);
        if (!frag->fragment)
                return -ENOMEM;

        res->data = frag;

        return 0;
}

static void string_stream_fragment_free(struct kunit_resource *res)
{
        struct string_stream_fragment *frag = res->data;

        list_del(&frag->node);
        kunit_kfree(frag->test, frag->fragment);
        kunit_kfree(frag->test, frag);
}

static struct string_stream_fragment *alloc_string_stream_fragment(
                struct kunit *test, int len, gfp_t gfp)
{
        struct string_stream_fragment_alloc_context context = {
                .test = test,
                .len = len,
                .gfp = gfp
        };

        return kunit_alloc_resource(test,
                                    string_stream_fragment_init,
                                    string_stream_fragment_free,
                                    gfp,
                                    &context);
}

static int string_stream_fragment_destroy(struct string_stream_fragment *frag)
{
        return kunit_destroy_resource(frag->test,
                                      kunit_resource_instance_match,
                                      frag);
}

int string_stream_vadd(struct string_stream *stream,
                       const char *fmt,
                       va_list args)
{
        struct string_stream_fragment *frag_container;
        int len;
        va_list args_for_counting;

        /* Make a copy because `vsnprintf` could change it */
        va_copy(args_for_counting, args);

        /* Need space for null byte. */
        len = vsnprintf(NULL, 0, fmt, args_for_counting) + 1;

        va_end(args_for_counting);

        frag_container = alloc_string_stream_fragment(stream->test,
                                                      len,
                                                      stream->gfp);
        if (!frag_container)
                return -ENOMEM;

        len = vsnprintf(frag_container->fragment, len, fmt, args);
        spin_lock(&stream->lock);
        stream->length += len;
        list_add_tail(&frag_container->node, &stream->fragments);
        spin_unlock(&stream->lock);

        return 0;
}

int string_stream_add(struct string_stream *stream, const char *fmt, ...)
{
        va_list args;
        int result;

        va_start(args, fmt);
        result = string_stream_vadd(stream, fmt, args);
        va_end(args);

        return result;
}

static void string_stream_clear(struct string_stream *stream)
{
        struct string_stream_fragment *frag_container, *frag_container_safe;

        spin_lock(&stream->lock);
        list_for_each_entry_safe(frag_container,
                                 frag_container_safe,
                                 &stream->fragments,
                                 node) {
                string_stream_fragment_destroy(frag_container);
        }
        stream->length = 0;
        spin_unlock(&stream->lock);
}

char *string_stream_get_string(struct string_stream *stream)
{
        struct string_stream_fragment *frag_container;
        size_t buf_len = stream->length + 1; /* +1 for null byte. */
        char *buf;

        buf = kunit_kzalloc(stream->test, buf_len, stream->gfp);
        if (!buf)
                return NULL;

        spin_lock(&stream->lock);
        list_for_each_entry(frag_container, &stream->fragments, node)
                strlcat(buf, frag_container->fragment, buf_len);
        spin_unlock(&stream->lock);

        return buf;
}

int string_stream_append(struct string_stream *stream,
                         struct string_stream *other)
{
        const char *other_content;

        other_content = string_stream_get_string(other);

        if (!other_content)
                return -ENOMEM;

        return string_stream_add(stream, other_content);
}

bool string_stream_is_empty(struct string_stream *stream)
{
        return list_empty(&stream->fragments);
}

struct string_stream_alloc_context {
        struct kunit *test;
        gfp_t gfp;
};

static int string_stream_init(struct kunit_resource *res, void *context)
{
        struct string_stream *stream;
        struct string_stream_alloc_context *ctx = context;

        stream = kunit_kzalloc(ctx->test, sizeof(*stream), ctx->gfp);
        if (!stream)
                return -ENOMEM;

        res->data = stream;
        stream->gfp = ctx->gfp;
        stream->test = ctx->test;
        INIT_LIST_HEAD(&stream->fragments);
        spin_lock_init(&stream->lock);

        return 0;
}

static void string_stream_free(struct kunit_resource *res)
{
        struct string_stream *stream = res->data;

        string_stream_clear(stream);
}

struct string_stream *alloc_string_stream(struct kunit *test, gfp_t gfp)
{
        struct string_stream_alloc_context context = {
                .test = test,
                .gfp = gfp
        };

        return kunit_alloc_resource(test,
                                    string_stream_init,
                                    string_stream_free,
                                    gfp,
                                    &context);
}

int string_stream_destroy(struct string_stream *stream)
{
        return kunit_destroy_resource(stream->test,
                                      kunit_resource_instance_match,
                                      stream);
}