#include "cache.h"
#include "repository.h"
#include "config.h"
#include "pkt-line.h"
#include "version.h"
#include "argv-array.h"
#include "ls-refs.h"
#include "serve.h"

static int always_advertise(struct repository *r,
                            struct strbuf *value)
{
        return 1;
}

static int agent_advertise(struct repository *r,
                           struct strbuf *value)
{
        if (value)
                strbuf_addstr(value, git_user_agent_sanitized());
        return 1;
}

struct protocol_capability {
        /*
         * The name of the capability.  The server uses this name when
         * advertising this capability, and the client uses this name to
         * specify this capability.
         */
        const char *name;

        /*
         * Function queried to see if a capability should be advertised.
         * Optionally a value can be specified by adding it to 'value'.
         * If a value is added to 'value', the server will advertise this
         * capability as "<name>=<value>" instead of "<name>".
         */
        int (*advertise)(struct repository *r, struct strbuf *value);

        /*
         * Function called when a client requests the capability as a command.
         * The function will be provided the capabilities requested via 'keys'
         * as well as a struct packet_reader 'request' which the command should
         * use to read the command specific part of the request.  Every command
         * MUST read until a flush packet is seen before sending a response.
         *
         * This field should be NULL for capabilities which are not commands.
         */
        int (*command)(struct repository *r,
                       struct argv_array *keys,
                       struct packet_reader *request);
};

static struct protocol_capability capabilities[] = {
        { "agent", agent_advertise, NULL },
        { "ls-refs", always_advertise, ls_refs },
};

static void advertise_capabilities(void)
{
        struct strbuf capability = STRBUF_INIT;
        struct strbuf value = STRBUF_INIT;
        int i;

        for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
                struct protocol_capability *c = &capabilities[i];

                if (c->advertise(the_repository, &value)) {
                        strbuf_addstr(&capability, c->name);

                        if (value.len) {
                                strbuf_addch(&capability, '=');
                                strbuf_addbuf(&capability, &value);
                        }

                        strbuf_addch(&capability, '\n');
                        packet_write(1, capability.buf, capability.len);
                }

                strbuf_reset(&capability);
                strbuf_reset(&value);
        }

        packet_flush(1);
        strbuf_release(&capability);
        strbuf_release(&value);
}

static struct protocol_capability *get_capability(const char *key)
{
        int i;

        if (!key)
                return NULL;

        for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
                struct protocol_capability *c = &capabilities[i];
                const char *out;
                if (skip_prefix(key, c->name, &out) && (!*out || *out == '='))
                        return c;
        }

        return NULL;
}

static int is_valid_capability(const char *key)
{
        const struct protocol_capability *c = get_capability(key);

        return c && c->advertise(the_repository, NULL);
}

static int is_command(const char *key, struct protocol_capability **command)
{
        const char *out;

        if (skip_prefix(key, "command=", &out)) {
                struct protocol_capability *cmd = get_capability(out);

                if (*command)
                        die("command '%s' requested after already requesting command '%s'",
                            out, (*command)->name);
                if (!cmd || !cmd->advertise(the_repository, NULL) || !cmd->command)
                        die("invalid command '%s'", out);

                *command = cmd;
                return 1;
        }

        return 0;
}

int has_capability(const struct argv_array *keys, const char *capability,
                   const char **value)
{
        int i;
        for (i = 0; i < keys->argc; i++) {
                const char *out;
                if (skip_prefix(keys->argv[i], capability, &out) &&
                    (!*out || *out == '=')) {
                        if (value) {
                                if (*out == '=')
                                        out++;
                                *value = out;
                        }
                        return 1;
                }
        }

        return 0;
}

enum request_state {
        PROCESS_REQUEST_KEYS,
        PROCESS_REQUEST_DONE,
};

static int process_request(void)
{
        enum request_state state = PROCESS_REQUEST_KEYS;
        struct packet_reader reader;
        struct argv_array keys = ARGV_ARRAY_INIT;
        struct protocol_capability *command = NULL;

        packet_reader_init(&reader, 0, NULL, 0,
                           PACKET_READ_CHOMP_NEWLINE |
                           PACKET_READ_GENTLE_ON_EOF);

        /*
         * Check to see if the client closed their end before sending another
         * request.  If so we can terminate the connection.
         */
        if (packet_reader_peek(&reader) == PACKET_READ_EOF)
                return 1;
        reader.options = PACKET_READ_CHOMP_NEWLINE;

        while (state != PROCESS_REQUEST_DONE) {
                switch (packet_reader_peek(&reader)) {
                case PACKET_READ_EOF:
                        BUG("Should have already died when seeing EOF");
                case PACKET_READ_NORMAL:
                        /* collect request; a sequence of keys and values */
                        if (is_command(reader.line, &command) ||
                            is_valid_capability(reader.line))
                                argv_array_push(&keys, reader.line);
                        else
                                die("unknown capability '%s'", reader.line);

                        /* Consume the peeked line */
                        packet_reader_read(&reader);
                        break;
                case PACKET_READ_FLUSH:
                        /*
                         * If no command and no keys were given then the client
                         * wanted to terminate the connection.
                         */
                        if (!keys.argc)
                                return 1;

                        /*
                         * The flush packet isn't consume here like it is in
                         * the other parts of this switch statement.  This is
                         * so that the command can read the flush packet and
                         * see the end of the request in the same way it would
                         * if command specific arguments were provided after a
                         * delim packet.
                         */
                        state = PROCESS_REQUEST_DONE;
                        break;
                case PACKET_READ_DELIM:
                        /* Consume the peeked line */
                        packet_reader_read(&reader);

                        state = PROCESS_REQUEST_DONE;
                        break;
                }
        }

        if (!command)
                die("no command requested");

        command->command(the_repository, &keys, &reader);

        argv_array_clear(&keys);
        return 0;
}

/* Main serve loop for protocol version 2 */
void serve(struct serve_options *options)
{
        if (options->advertise_capabilities || !options->stateless_rpc) {
                /* serve by default supports v2 */
                packet_write_fmt(1, "version 2\n");

                advertise_capabilities();
                /*
                 * If only the list of capabilities was requested exit
                 * immediately after advertising capabilities
                 */
                if (options->advertise_capabilities)
                        return;
        }

        /*
         * If stateless-rpc was requested then exit after
         * a single request/response exchange
         */
        if (options->stateless_rpc) {
                process_request();
        } else {
                for (;;)
                        if (process_request())
                                break;
        }
}