/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */

#include "imap-common.h"
#include "buffer.h"
#include "str.h"
#include "strescape.h"
#include "istream.h"
#include "ostream.h"
#include "istream-header-filter.h"
#include "message-parser.h"
#include "mail-storage-private.h"
#include "imap-quote.h"
#include "imap-parser.h"
#include "imap-msgpart.h"
#include "imap-fetch.h"

#include <ctype.h>
#include <unistd.h>

struct imap_fetch_body_data {
	const char *section; /* NOTE: always uppercased */
	struct imap_msgpart *msgpart;

	bool partial:1;
	bool binary:1;
	bool binary_size:1;
};

struct imap_fetch_preview_data {
	/* If TRUE, lazy modifier is specified. */
	bool lazy:1;
	/* Uses the pre-RFC 8970 standard (requires algorithm to be returned
	 * as part of FETCH response). */
	bool old_standard:1;
	/* If TRUE, uses "PREVIEW" command; if FALSE, uses older "SNIPPET"
	 * command. */
	bool preview_cmd:1;
};

static void fetch_read_error(struct imap_fetch_context *ctx,
			     const char **disconnect_reason_r)
{
	struct imap_fetch_state *state = &ctx->state;

	if (state->cur_input->stream_errno == ENOENT) {
		if (state->cur_mail->expunged) {
			*disconnect_reason_r = "Mail expunged while it was being FETCHed";
			return;
		}
	}
	mail_set_critical(state->cur_mail,
		"read(%s) failed: %s (FETCH %s)",
		i_stream_get_name(state->cur_input),
		i_stream_get_error(state->cur_input),
		state->cur_human_name);
	*disconnect_reason_r = "FETCH read() failed";
}

static const char *get_body_name(const struct imap_fetch_body_data *body)
{
	string_t *str;

	str = t_str_new(128);
	if (body->binary_size)
		str_append(str, "BINARY.SIZE");
	else if (body->binary)
		str_append(str, "BINARY");
	else
		str_append(str, "BODY");
	str_printfa(str, "[%s]", body->section);
	if (body->partial) {
		str_printfa(str, "<%"PRIuUOFF_T">",
			    imap_msgpart_get_partial_offset(body->msgpart));
	}
	return str_c(str);
}

static string_t *get_prefix(struct imap_fetch_state *state,
			    const struct imap_fetch_body_data *body,
			    uoff_t size, bool has_nuls)
{
	string_t *str;

	str = t_str_new(128);
	if (state->cur_first)
		state->cur_first = FALSE;
	else
		str_append_c(str, ' ');

	str_append(str, get_body_name(body));

	if (size == UOFF_T_MAX)
		str_append(str, " NIL");
	else if (has_nuls && body->binary)
		str_printfa(str, " ~{%"PRIuUOFF_T"}\r\n", size);
	else
		str_printfa(str, " {%"PRIuUOFF_T"}\r\n", size);
	return str;
}

static int fetch_stream_continue(struct imap_fetch_context *ctx)
{
	struct imap_fetch_state *state = &ctx->state;
	const char *disconnect_reason;
	uoff_t orig_input_offset = state->cur_input->v_offset;
	enum ostream_send_istream_result res;

	o_stream_set_max_buffer_size(ctx->client->output, 0);
	res = o_stream_send_istream(ctx->client->output, state->cur_input);
	o_stream_set_max_buffer_size(ctx->client->output, SIZE_MAX);

	if (ctx->state.cur_stats_sizep != NULL) {
		*ctx->state.cur_stats_sizep +=
			state->cur_input->v_offset - orig_input_offset;
	}

	switch (res) {
	case OSTREAM_SEND_ISTREAM_RESULT_FINISHED:
		if (state->cur_input->v_offset != state->cur_size) {
			/* Input stream gave less data than expected */
			mail_set_cache_corrupted(state->cur_mail,
				state->cur_size_field, t_strdup_printf(
				"read(%s): FETCH %s got too little data: "
				"%"PRIuUOFF_T" vs %"PRIuUOFF_T,
				i_stream_get_name(state->cur_input),
				state->cur_human_name,
				state->cur_input->v_offset, state->cur_size));
			client_disconnect(ctx->client, "FETCH failed");
			return -1;
		}
		return 1;
	case OSTREAM_SEND_ISTREAM_RESULT_WAIT_INPUT:
		i_unreached();
	case OSTREAM_SEND_ISTREAM_RESULT_WAIT_OUTPUT:
		return 0;
	case OSTREAM_SEND_ISTREAM_RESULT_ERROR_INPUT:
		fetch_read_error(ctx, &disconnect_reason);
		client_disconnect(ctx->client, disconnect_reason);
		return -1;
	case OSTREAM_SEND_ISTREAM_RESULT_ERROR_OUTPUT:
		/* client disconnected */
		return -1;
	}
	i_unreached();
}

static const char *
get_body_human_name(pool_t pool, struct imap_fetch_body_data *body)
{
	string_t *str;
	uoff_t partial_offset, partial_size;

	str = t_str_new(64);
	if (body->binary)
		str_append(str, "BINARY[");
	else
		str_append(str, "BODY[");
	str_append(str, body->section);
	str_append_c(str, ']');

	partial_offset = imap_msgpart_get_partial_offset(body->msgpart);
	partial_size = imap_msgpart_get_partial_size(body->msgpart);
	if (partial_offset != 0 || partial_size != UOFF_T_MAX) {
		str_printfa(str, "<%"PRIuUOFF_T, partial_offset);
		if (partial_size != UOFF_T_MAX)
			str_printfa(str, ".%"PRIuUOFF_T, partial_size);
		str_append_c(str, '>');
	}
	return p_strdup(pool, str_c(str));
}

static void fetch_state_update_stats(struct imap_fetch_context *ctx,
				     const struct imap_msgpart *msgpart)
{
	if (!imap_msgpart_contains_body(msgpart)) {
		ctx->client->fetch_hdr_count++;
		ctx->state.cur_stats_sizep = &ctx->client->fetch_hdr_bytes;
	} else {
		ctx->client->fetch_body_count++;
		ctx->state.cur_stats_sizep = &ctx->client->fetch_body_bytes;
	}
}

static int fetch_body_msgpart(struct imap_fetch_context *ctx, struct mail *mail,
			      struct imap_fetch_body_data *body)
{
	struct imap_msgpart_open_result result;
	string_t *str;

	if (mail == NULL) {
		imap_msgpart_free(&body->msgpart);
		return 1;
	}

	if (imap_msgpart_open(mail, body->msgpart, &result) < 0)
		return -1;
	i_assert(result.input->v_offset == 0);
	ctx->state.cur_input = result.input;
	ctx->state.cur_size = result.size;
	ctx->state.cur_size_field = result.size_field;
	ctx->state.cur_human_name = get_body_human_name(ctx->ctx_pool, body);

	fetch_state_update_stats(ctx, body->msgpart);
	str = get_prefix(&ctx->state, body, ctx->state.cur_size,
			 result.binary_decoded_input_has_nuls);
	o_stream_nsend(ctx->client->output, str_data(str), str_len(str));

	ctx->state.cont_handler = fetch_stream_continue;
	return ctx->state.cont_handler(ctx);
}

static int fetch_binary_size(struct imap_fetch_context *ctx, struct mail *mail,
			     struct imap_fetch_body_data *body)
{
	string_t *str;
	uoff_t size;

	if (mail == NULL) {
		imap_msgpart_free(&body->msgpart);
		return 1;
	}

	if (imap_msgpart_size(mail, body->msgpart, &size) < 0)
		return -1;

	str = t_str_new(128);
	if (ctx->state.cur_first)
		ctx->state.cur_first = FALSE;
	else
		str_append_c(str, ' ');
	str_printfa(str, "%s %"PRIuUOFF_T, get_body_name(body), size);

	if (o_stream_send(ctx->client->output, str_data(str), str_len(str)) < 0)
		return -1;
	return 1;
}

/* Parse next digits in string into integer. Returns -1 if the integer
   becomes too big and wraps. */
static int read_uoff_t(const char **p, uoff_t *value)
{
	return str_parse_uoff(*p, value, p);
}

static int
body_header_fields_parse(struct imap_fetch_init_context *ctx,
			 struct imap_fetch_body_data *body, const char *prefix,
			 const struct imap_arg *args, unsigned int args_count)
{
	string_t *str;
	const char *value;
	size_t i;

	ctx->fetch_ctx->fetch_header_fields = TRUE;

	str = str_new(ctx->pool, 128);
	str_append(str, prefix);
	str_append(str, " (");

	for (i = 0; i < args_count; i++) {
		if (!imap_arg_get_astring(&args[i], &value)) {
			ctx->error = "Invalid BODY[..] parameter: "
				"Header list contains non-strings";
			return -1;
		}
		value = t_str_ucase(value);

		if (i != 0)
			str_append_c(str, ' ');

		if (args[i].type == IMAP_ARG_ATOM)
			str_append(str, value);
		else
			imap_append_quoted(str, value);
	}
	str_append_c(str, ')');
	body->section = str_c(str);
	return 0;
}

static int body_parse_partial(struct imap_fetch_body_data *body,
			      const char *p, const char **error_r)
{
	uoff_t offset, size = UOFF_T_MAX;

	if (*p == '\0')
		return 0;
	/* <start.end> */
	if (*p != '<') {
		*error_r = "Unexpected data after ']'";
		return -1;
	}

	p++;
	body->partial = TRUE;

	if (read_uoff_t(&p, &offset) < 0 || offset > OFF_T_MAX) {
		/* wrapped */
		*error_r = "Too big partial start";
		return -1;
	}

	if (*p == '.') {
		p++;
		if (read_uoff_t(&p, &size) < 0 || size > OFF_T_MAX) {
			/* wrapped */
			*error_r = "Too big partial end";
			return -1;
		}
	}

	if (*p != '>') {
		*error_r = "Missing '>' in partial";
		return -1;
	}
	if (p[1] != '\0') {
		*error_r = "Unexpected data after '>'";
		return -1;
	}
	imap_msgpart_set_partial(body->msgpart, offset, size);
	return 0;
}

bool imap_fetch_body_section_init(struct imap_fetch_init_context *ctx)
{
	struct imap_fetch_body_data *body;
	const struct imap_arg *list_args;
	unsigned int list_count;
	const char *str, *p, *error;

	i_assert(str_begins(ctx->name, "BODY"));
	p = ctx->name + 4;

	body = p_new(ctx->pool, struct imap_fetch_body_data, 1);

	if (str_begins(p, ".PEEK"))
		p += 5;
	else
		ctx->fetch_ctx->flags_update_seen = TRUE;
	if (*p != '[') {
		ctx->error = "Invalid BODY[..] parameter: Missing '['";
		return FALSE;
	}

	if (imap_arg_get_list_full(&ctx->args[0], &list_args, &list_count)) {
		/* BODY[HEADER.FIELDS.. (headers list)] */
		if (!imap_arg_get_atom(&ctx->args[1], &str) ||
		    str[0] != ']') {
			ctx->error = "Invalid BODY[..] parameter: Missing ']'";
			return FALSE;
		}
		if (body_header_fields_parse(ctx, body, p+1,
					     list_args, list_count) < 0)
			return FALSE;
		p = str+1;
		ctx->args += 2;
	} else {
		/* no headers list */
		body->section = p+1;
		p = strchr(body->section, ']');
		if (p == NULL) {
			ctx->error = "Invalid BODY[..] parameter: Missing ']'";
			return FALSE;
		}
		body->section = p_strdup_until(ctx->pool, body->section, p);
		p++;
	}
	if (imap_msgpart_parse(body->section, &body->msgpart) < 0) {
		ctx->error = "Invalid BODY[..] section";
		return FALSE;
	}
	ctx->fetch_ctx->fetch_data |=
		imap_msgpart_get_fetch_data(body->msgpart);
	imap_msgpart_get_wanted_headers(body->msgpart, &ctx->fetch_ctx->all_headers);

	if (body_parse_partial(body, p, &error) < 0) {
		ctx->error = p_strdup_printf(ctx->pool,
			"Invalid BODY[..] parameter: %s", error);
		return FALSE;
	}

	/* update the section name for the imap_fetch_add_handler() */
	ctx->name = p_strdup(ctx->pool, get_body_name(body));
	imap_fetch_add_handler(ctx, IMAP_FETCH_HANDLER_FLAG_WANT_DEINIT,
			       "NIL", fetch_body_msgpart, body);
	return TRUE;
}

bool imap_fetch_binary_init(struct imap_fetch_init_context *ctx)
{
	struct imap_fetch_body_data *body;
	const struct imap_arg *list_args;
	unsigned int list_count;
	const char *str, *p, *error;

	i_assert(str_begins(ctx->name, "BINARY"));
	p = ctx->name + 6;

	body = p_new(ctx->pool, struct imap_fetch_body_data, 1);
	body->binary = TRUE;

	if (str_begins(p, ".SIZE")) {
		/* fetch decoded size of the section */
		p += 5;
		body->binary_size = TRUE;
	} else if (str_begins(p, ".PEEK")) {
		p += 5;
	} else {
		ctx->fetch_ctx->flags_update_seen = TRUE;
	}
	if (*p != '[') {
		ctx->error = "Invalid BINARY[..] parameter: Missing '['";
		return FALSE;
	}

	if (imap_arg_get_list_full(&ctx->args[0], &list_args, &list_count)) {
		/* BINARY[HEADER.FIELDS.. (headers list)] */
		if (!imap_arg_get_atom(&ctx->args[1], &str) ||
		    str[0] != ']') {
			ctx->error = "Invalid BINARY[..] parameter: Missing ']'";
			return FALSE;
		}
		if (body_header_fields_parse(ctx, body, p+1,
					     list_args, list_count) < 0)
			return FALSE;
		p = str+1;
		ctx->args += 2;
	} else {
		/* no headers list */
		body->section = p+1;
		p = strchr(body->section, ']');
		if (p == NULL) {
			ctx->error = "Invalid BINARY[..] parameter: Missing ']'";
			return FALSE;
		}
		body->section = p_strdup_until(ctx->pool, body->section, p);
		p++;
	}
	if (imap_msgpart_parse(body->section, &body->msgpart) < 0) {
		ctx->error = "Invalid BINARY[..] section";
		return FALSE;
	}
	imap_msgpart_set_decode_to_binary(body->msgpart);
	ctx->fetch_ctx->fetch_data |=
		imap_msgpart_get_fetch_data(body->msgpart);

	if (!body->binary_size) {
		if (body_parse_partial(body, p, &error) < 0) {
			ctx->error = p_strdup_printf(ctx->pool,
				"Invalid BINARY[..] parameter: %s", error);
			return FALSE;
		}
	}

	/* update the section name for the imap_fetch_add_handler() */
	ctx->name = p_strdup(ctx->pool, get_body_name(body));
	if (body->binary_size) {
		imap_fetch_add_handler(ctx, IMAP_FETCH_HANDLER_FLAG_WANT_DEINIT,
				       "0", fetch_binary_size, body);
	} else {
		imap_fetch_add_handler(ctx, IMAP_FETCH_HANDLER_FLAG_WANT_DEINIT,
				       "NIL", fetch_body_msgpart, body);
	}
	return TRUE;
}

static int ATTR_NULL(3)
fetch_rfc822_size(struct imap_fetch_context *ctx, struct mail *mail,
		  void *context ATTR_UNUSED)
{
	uoff_t size;

	if (mail_get_virtual_size(mail, &size) < 0)
		return -1;

	str_printfa(ctx->state.cur_str, "RFC822.SIZE %"PRIuUOFF_T" ", size);
	return 1;
}

static int
fetch_and_free_msgpart(struct imap_fetch_context *ctx,
		       struct mail *mail, struct imap_msgpart **_msgpart)
{
	struct imap_msgpart_open_result result;
	int ret;

	ret = imap_msgpart_open(mail, *_msgpart, &result);
	imap_msgpart_free(_msgpart);
	if (ret < 0)
		return -1;
	i_assert(result.input->v_offset == 0);
	ctx->state.cur_input = result.input;
	ctx->state.cur_size = result.size;
	ctx->state.cur_size_field = result.size_field;
	ctx->state.cont_handler = fetch_stream_continue;
	return 0;
}

static int ATTR_NULL(3)
fetch_rfc822(struct imap_fetch_context *ctx, struct mail *mail,
	     void *context ATTR_UNUSED)
{
	struct imap_msgpart *msgpart;
	const char *str;

	msgpart = imap_msgpart_full();
	fetch_state_update_stats(ctx, msgpart);
	if (fetch_and_free_msgpart(ctx, mail, &msgpart) < 0)
		return -1;

	str = t_strdup_printf(" RFC822 {%"PRIuUOFF_T"}\r\n",
			      ctx->state.cur_size);
	if (ctx->state.cur_first) {
		str++; ctx->state.cur_first = FALSE;
	}
	o_stream_nsend_str(ctx->client->output, str);

	ctx->state.cur_human_name = "RFC822";
	return ctx->state.cont_handler(ctx);
}

static int ATTR_NULL(3)
fetch_rfc822_header(struct imap_fetch_context *ctx,
		    struct mail *mail, void *context ATTR_UNUSED)
{
	struct imap_msgpart *msgpart;
	const char *str;

	msgpart = imap_msgpart_header();
	fetch_state_update_stats(ctx, msgpart);
	if (fetch_and_free_msgpart(ctx, mail, &msgpart) < 0)
		return -1;

	str = t_strdup_printf(" RFC822.HEADER {%"PRIuUOFF_T"}\r\n",
			      ctx->state.cur_size);
	if (ctx->state.cur_first) {
		str++; ctx->state.cur_first = FALSE;
	}
	o_stream_nsend_str(ctx->client->output, str);

	ctx->state.cur_human_name = "RFC822.HEADER";
	return ctx->state.cont_handler(ctx);
}

static int ATTR_NULL(3)
fetch_rfc822_text(struct imap_fetch_context *ctx, struct mail *mail,
		  void *context ATTR_UNUSED)
{
	struct imap_msgpart *msgpart;
	const char *str;

	msgpart = imap_msgpart_body();
	fetch_state_update_stats(ctx, msgpart);
	if (fetch_and_free_msgpart(ctx, mail, &msgpart) < 0)
		return -1;

	str = t_strdup_printf(" RFC822.TEXT {%"PRIuUOFF_T"}\r\n",
			      ctx->state.cur_size);
	if (ctx->state.cur_first) {
		str++; ctx->state.cur_first = FALSE;
	}
	o_stream_nsend_str(ctx->client->output, str);

	ctx->state.cur_human_name = "RFC822.TEXT";
	return ctx->state.cont_handler(ctx);
}

bool imap_fetch_rfc822_init(struct imap_fetch_init_context *ctx)
{
	const char *name = ctx->name;

	if (name[6] == '\0') {
		ctx->fetch_ctx->fetch_data |= MAIL_FETCH_STREAM_HEADER |
			MAIL_FETCH_STREAM_BODY;
		ctx->fetch_ctx->flags_update_seen = TRUE;
		imap_fetch_add_handler(ctx, 0, "NIL",
				       fetch_rfc822, NULL);
		return TRUE;
	}

	if (strcmp(name+6, ".SIZE") == 0) {
		ctx->fetch_ctx->fetch_data |= MAIL_FETCH_VIRTUAL_SIZE;
		imap_fetch_add_handler(ctx, IMAP_FETCH_HANDLER_FLAG_BUFFERED,
				       "0", fetch_rfc822_size, NULL);
		return TRUE;
	}
	if (strcmp(name+6, ".HEADER") == 0) {
		ctx->fetch_ctx->fetch_data |= MAIL_FETCH_STREAM_HEADER;
		imap_fetch_add_handler(ctx, 0, "NIL",
				       fetch_rfc822_header, NULL);
		return TRUE;
	}
	if (strcmp(name+6, ".TEXT") == 0) {
		ctx->fetch_ctx->fetch_data |= MAIL_FETCH_STREAM_BODY;
		ctx->fetch_ctx->flags_update_seen = TRUE;
		imap_fetch_add_handler(ctx, 0, "NIL",
				       fetch_rfc822_text, NULL);
		return TRUE;
	}

	ctx->error = t_strconcat("Unknown parameter ", name, NULL);
	return FALSE;
}

static int ATTR_NULL(3)
fetch_snippet(struct imap_fetch_context *ctx, struct mail *mail,
	      struct imap_fetch_preview_data *preview)
{
	enum mail_lookup_abort temp_lookup_abort = preview->lazy ? MAIL_LOOKUP_ABORT_NOT_IN_CACHE_START_CACHING : mail->lookup_abort;
	enum mail_lookup_abort orig_lookup_abort = mail->lookup_abort;
	const char *resp, *snippet;
	int ret;

	mail->lookup_abort = temp_lookup_abort;
	ret = mail_get_special(mail, MAIL_FETCH_BODY_SNIPPET, &snippet);
	mail->lookup_abort = orig_lookup_abort;

	resp = preview->preview_cmd ? "PREVIEW" : "SNIPPET";

	if (ret == 0) {
		/* got it => nothing to do */
		snippet++; /* skip over snippet version byte */
	} else if (mailbox_get_last_mail_error(mail->box) != MAIL_ERROR_LOOKUP_ABORTED) {
		/* actual error => bail */
		return -1;
	} else {
		/*
		 * Two ways to get here:
		 * - not in cache && lazy => give up
		 * - not in cache && !lazy => someone higher up set
		 *   MAIL_LOOKUP_ABORT_NOT_IN_CACHE and so even though we got
		 *   a non-lazy request we failed the cache lookup.
		 *
		 *   This is not an error, but since the scenario is
		 *   sufficiently convoluted this else branch serves to
		 *   document it.
		 *
		 * This path will return NIL as the preview response.
		 */
	}

	str_append(ctx->state.cur_str, resp);
	if (preview->old_standard)
		str_append(ctx->state.cur_str, " (FUZZY ");
	else
		str_append(ctx->state.cur_str, " ");
	if (ret == 0)
		imap_append_string(ctx->state.cur_str, snippet);
	else
		str_append(ctx->state.cur_str, "NIL");
	if (preview->old_standard)
		str_append(ctx->state.cur_str, ")");
	str_append_c(ctx->state.cur_str, ' ');

	return 1;
}

static bool fetch_preview_init(struct imap_fetch_init_context *ctx,
			       bool preview_cmd)
{
	const struct imap_arg *list_args;
	unsigned int list_count;
	struct imap_fetch_preview_data *preview;

	preview = p_new(ctx->pool, struct imap_fetch_preview_data, 1);
	preview->preview_cmd = preview_cmd;
	/* We can tell we are using the "Old" (pre-RFC 8970) standard
	 * if:
	 * 1) SNIPPET command is used
	 * 2) FUZZY algorithm is explicitly requested
	 * The one usage we cannot catch is if PREVIEW command is used, and
	 * no algorithm is specified - the pre-RFC standard requires that the
	 * algorithm must be output as part of the response; the RFC standard
	 * does not output the algorithm. There is unfortunately nothing we
	 * can do about this, so we need to send the standards compliant
	 * way. */
	preview->old_standard = !preview_cmd;

	if (imap_arg_get_list_full(&ctx->args[0], &list_args, &list_count)) {
		unsigned int i;

		for (i = 0; i < list_count; i++) {
			const char *str;

			if (!imap_arg_get_atom(&list_args[i], &str)) {
				ctx->error = "Invalid PREVIEW modifier";
				return FALSE;
			}

			if (strcasecmp(str, "LAZY") == 0) {
				preview->lazy = TRUE;
			} else if (strcasecmp(str, "LAZY=FUZZY") == 0) {
				preview->lazy = TRUE;
				preview->old_standard = TRUE;
			} else if (strcasecmp(str, "FUZZY") == 0) {
				preview->old_standard = TRUE;
			} else {
				ctx->error = t_strdup_printf("'%s' is not a "
							     "supported PREVIEW modifier",
							     str);
				return FALSE;
			}
		}

		ctx->args += list_count;
	}

	ctx->fetch_ctx->fetch_data |= MAIL_FETCH_BODY_SNIPPET;
	imap_fetch_add_handler(ctx, IMAP_FETCH_HANDLER_FLAG_BUFFERED,
			       "NIL", fetch_snippet, preview);
	return TRUE;
}

bool imap_fetch_preview_init(struct imap_fetch_init_context *ctx)
{
	return fetch_preview_init(ctx, TRUE);
}

bool imap_fetch_snippet_init(struct imap_fetch_init_context *ctx)
{
	return fetch_preview_init(ctx, FALSE);
}