#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>

#include "web.h"

/* Copies at most cap-1 bytes of [s, s+n) into out; -1 when it does not fit. */
static int copy_n(char *out, size_t cap, const char *s, size_t n)
{
    if (!cap || n >= cap)
        return -1;
    memcpy(out, s, n);
    out[n] = '\0';
    return 0;
}

/* Value of header `name` (case-insensitive) in [h, end), trimmed. */
static int header_get(const char *h, const char *end, const char *name,
                      char *out, size_t cap)
{
    size_t nl = strlen(name);
    while (h < end) {
        const char *eol = memchr(h, '\n', (size_t)(end - h));
        if (!eol)
            eol = end;
        const char *line_end = eol > h && eol[-1] == '\r' ? eol - 1 : eol;
        if ((size_t)(line_end - h) > nl && h[nl] == ':' &&
            strncasecmp(h, name, nl) == 0) {
            const char *v = h + nl + 1;
            while (v < line_end && (*v == ' ' || *v == '\t'))
                v++;
            const char *ve = line_end;
            while (ve > v && (ve[-1] == ' ' || ve[-1] == '\t'))
                ve--;
            return copy_n(out, cap, v, (size_t)(ve - v));
        }
        h = eol + 1;
    }
    if (cap)
        out[0] = '\0';
    return -1;
}

int web_parse_request(const char *buf, size_t n, struct web_req *r)
{
    memset(r, 0, sizeof *r);
    if (n > WEB_MAX_REQUEST)
        return -1;
    const char *hend = NULL;
    for (size_t i = 0; i + 3 < n; i++)
        if (memcmp(buf + i, "\r\n\r\n", 4) == 0) {
            hend = buf + i + 4;
            break;
        }
    if (!hend)
        return n >= WEB_MAX_REQUEST ? -1 : 1;

    /* request line: METHOD SP TARGET SP HTTP/x.y */
    const char *sp1 = memchr(buf, ' ', (size_t)(hend - buf));
    if (!sp1 || copy_n(r->method, sizeof r->method, buf,
                       (size_t)(sp1 - buf)) != 0)
        return -1;
    const char *tgt = sp1 + 1;
    const char *sp2 = memchr(tgt, ' ', (size_t)(hend - tgt));
    if (!sp2 || sp2 == tgt || *tgt != '/')
        return -1;
    const char *q = memchr(tgt, '?', (size_t)(sp2 - tgt));
    const char *pend = q ? q : sp2;
    if (copy_n(r->path, sizeof r->path, tgt, (size_t)(pend - tgt)) != 0)
        return -1;
    if (q && copy_n(r->query, sizeof r->query, q + 1,
                    (size_t)(sp2 - q - 1)) != 0)
        return -1;
    if (strncmp(sp2 + 1, "HTTP/1.", 7) != 0)
        return -1;

    const char *hdrs = memchr(sp2, '\n', (size_t)(hend - sp2));
    if (!hdrs)
        return -1;
    hdrs++;
    header_get(hdrs, hend, "Cookie", r->cookie, sizeof r->cookie);
    header_get(hdrs, hend, "X-Forwarded-For", r->forwarded_for,
               sizeof r->forwarded_for);
    header_get(hdrs, hend, "X-Forwarded-Uri", r->forwarded_uri,
               sizeof r->forwarded_uri);
    char cl[32];
    size_t body_len = 0;
    if (header_get(hdrs, hend, "Content-Length", cl, sizeof cl) == 0) {
        char *e = NULL;
        long long v = strtoll(cl, &e, 10);
        if (!*cl || *e || v < 0 || v > WEB_MAX_REQUEST)
            return -1;
        body_len = (size_t)v;
    }
    char te[32];
    if (header_get(hdrs, hend, "Transfer-Encoding", te, sizeof te) == 0)
        return -1; /* chunked bodies are not needed here */
    size_t have = n - (size_t)(hend - buf);
    if (have < body_len)
        return (size_t)(hend - buf) + body_len > WEB_MAX_REQUEST ? -1 : 1;
    r->body = hend;
    r->body_len = body_len;
    return 0;
}

static int hexval(char c)
{
    if (c >= '0' && c <= '9')
        return c - '0';
    if (c >= 'a' && c <= 'f')
        return c - 'a' + 10;
    if (c >= 'A' && c <= 'F')
        return c - 'A' + 10;
    return -1;
}

int web_form_get(const char *form, size_t len, const char *key, char *out,
                 size_t cap)
{
    size_t kl = strlen(key);
    const char *p = form, *end = form + len;
    while (p < end) {
        const char *amp = memchr(p, '&', (size_t)(end - p));
        const char *pe = amp ? amp : end;
        const char *eq = memchr(p, '=', (size_t)(pe - p));
        if (eq && (size_t)(eq - p) == kl && memcmp(p, key, kl) == 0) {
            size_t o = 0;
            for (const char *v = eq + 1; v < pe; v++) {
                char c = *v;
                if (c == '+') {
                    c = ' ';
                } else if (c == '%') {
                    if (pe - v < 3)
                        return -1;
                    int hi = hexval(v[1]), lo = hexval(v[2]);
                    if (hi < 0 || lo < 0)
                        return -1;
                    c = (char)(hi * 16 + lo);
                    if (!c)
                        return -1;
                    v += 2;
                }
                if (o + 1 >= cap)
                    return -1;
                out[o++] = c;
            }
            out[o] = '\0';
            return 0;
        }
        p = pe + 1;
    }
    return -1;
}

int web_cookie_get(const char *header, const char *name, char *out,
                   size_t cap)
{
    size_t nl = strlen(name);
    const char *p = header;
    while (p && *p) {
        while (*p == ' ' || *p == ';')
            p++;
        const char *semi = strchr(p, ';');
        const char *pe = semi ? semi : p + strlen(p);
        if ((size_t)(pe - p) > nl && p[nl] == '=' &&
            strncmp(p, name, nl) == 0)
            return copy_n(out, cap, p + nl + 1, (size_t)(pe - p - nl - 1));
        p = semi ? semi + 1 : NULL;
    }
    return -1;
}

void web_html_escape(struct buf *b, const char *s)
{
    for (; s && *s; s++) {
        switch (*s) {
        case '&':
            buf_append(b, "&amp;", 5);
            break;
        case '<':
            buf_append(b, "&lt;", 4);
            break;
        case '>':
            buf_append(b, "&gt;", 4);
            break;
        case '"':
            buf_append(b, "&quot;", 6);
            break;
        case '\'':
            buf_append(b, "&#39;", 5);
            break;
        default:
            buf_append(b, s, 1);
        }
    }
}

int web_token_ok(const char *s)
{
    if (!s || !*s)
        return 0;
    for (; *s; s++)
        if (!((*s >= 'A' && *s <= 'Z') || (*s >= 'a' && *s <= 'z') ||
              (*s >= '0' && *s <= '9') || *s == '_' || *s == '-'))
            return 0;
    return 1;
}

/* --- sessions ------------------------------------------------------ */

static int session_live(const struct web_session *s, int64_t now)
{
    return s->token[0] && now - s->created < WEB_SESSION_TTL;
}

struct web_session *web_store_add(struct web_store *st, const char *bokf,
                                  const char *user, int64_t now)
{
    struct web_session *slot = NULL;
    for (int i = 0; i < WEB_MAX_SESSIONS && !slot; i++)
        if (!session_live(&st->s[i], now))
            slot = &st->s[i];
    if (!slot) { /* full: replace the oldest */
        slot = &st->s[0];
        for (int i = 1; i < WEB_MAX_SESSIONS; i++)
            if (st->s[i].created < slot->created)
                slot = &st->s[i];
    }
    memset(slot, 0, sizeof *slot);
    char *tok = util_random_id("", 32);
    char *hdl = util_random_id("", 24);
    snprintf(slot->token, sizeof slot->token, "%s", tok);
    snprintf(slot->handle, sizeof slot->handle, "%s", hdl);
    free(tok);
    free(hdl);
    snprintf(slot->bokf, sizeof slot->bokf, "%s", bokf);
    snprintf(slot->user, sizeof slot->user, "%s", user ? user : "");
    slot->created = now;
    return slot;
}

static struct web_session *store_find(struct web_store *st, const char *v,
                                      int by_handle, int64_t now)
{
    if (!web_token_ok(v))
        return NULL;
    size_t vl = strlen(v);
    for (int i = 0; i < WEB_MAX_SESSIONS; i++) {
        struct web_session *s = &st->s[i];
        const char *k = by_handle ? s->handle : s->token;
        if (session_live(s, now) && strlen(k) == vl &&
            util_const_eq(k, v, vl))
            return s;
    }
    return NULL;
}

struct web_session *web_store_by_token(struct web_store *st,
                                       const char *token, int64_t now)
{
    return store_find(st, token, 0, now);
}

struct web_session *web_store_by_handle(struct web_store *st,
                                        const char *handle, int64_t now)
{
    return store_find(st, handle, 1, now);
}

void web_store_del(struct web_session *s)
{
    if (s)
        memset(s, 0, sizeof *s);
}

/* --- limiter ------------------------------------------------------- */

static struct web_rl_entry *rl_find(struct web_rl *rl, const char *addr)
{
    for (int i = 0; i < WEB_RL_SLOTS; i++)
        if (rl->e[i].addr[0] && strcmp(rl->e[i].addr, addr) == 0)
            return &rl->e[i];
    return NULL;
}

int64_t web_rl_blocked(const struct web_rl *rl, const char *addr,
                       int64_t now)
{
    for (int i = 0; i < WEB_RL_SLOTS; i++) {
        const struct web_rl_entry *e = &rl->e[i];
        if (e->addr[0] && strcmp(e->addr, addr) == 0)
            return e->fails >= WEB_RL_MAX_FAILS && e->window_end > now
                       ? e->window_end - now
                       : 0;
    }
    return 0;
}

void web_rl_fail(struct web_rl *rl, const char *addr, int64_t now)
{
    struct web_rl_entry *e = rl_find(rl, addr);
    if (!e) {
        /* a free or expired slot, else the one whose window ends first */
        e = &rl->e[0];
        for (int i = 0; i < WEB_RL_SLOTS; i++) {
            struct web_rl_entry *c = &rl->e[i];
            if (!c->addr[0] || c->window_end <= now) {
                e = c;
                break;
            }
            if (c->window_end < e->window_end)
                e = c;
        }
        memset(e, 0, sizeof *e);
        snprintf(e->addr, sizeof e->addr, "%s", addr);
    }
    if (e->fails == 0 || e->window_end <= now) {
        e->fails = 0;
        e->window_end = now + WEB_RL_WINDOW;
    }
    e->fails++;
}

void web_rl_ok(struct web_rl *rl, const char *addr)
{
    struct web_rl_entry *e = rl_find(rl, addr);
    if (e)
        memset(e, 0, sizeof *e);
}