/* bt_dev.c — 蓝牙 A2DP 端点选择 + PCM 名构造 + 回落退避（纯逻辑实现，见 bt_dev.h 契约）。
 *
 * 纯 libc（string / stdlib），无任何 meow_* 调用、无 popen、无文件 I/O —— meow_audiod 负责
 * 执行 `bluealsa-cli list-pcms`、调用 libasound 及维护运行时状态。
 */
#include "bt_dev.h"

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

/* 是否 a2dpsrc / a2dp_source 端点行（bluealsa 4.1.1 list-pcms 的端点头）。
 * ⚠️ 必须**行内**判定：直接对整串 strstr 会让「本行」借到「下一行」里的 a2dpsrc
 * （真机 hfphf/source 行会被误判成 A2DP 源端点——M50 实测踩到）。 */
static int line_is_src(const char *ln)
{
    const char *nl = strchr(ln, '\n');
    size_t len = nl ? (size_t)(nl - ln) : strlen(ln);
    char line[256];
    if (len >= sizeof line) len = sizeof line - 1;
    memcpy(line, ln, len);
    line[len] = 0;
    const char *p = line;
    while (*p == ' ' || *p == '\t') p++;
    return strstr(p, "a2dpsrc") != NULL || strstr(p, "a2dp_source") != NULL;
}

/* 从 `hcitool con` 输出取第一条 ACL 连接的对端 BD_ADDR。
 * 内核 ACL 是「设备是否真的连着」的权威（M45/M49 结论）；bluealsa 的 list-pcms 只在
 * profile 配置好后的**秒级窗口**里存在，不能当 MAC 的唯一来源（M50 真机实测）。
 * 行形如：`\t< ACL 33:DE:2E:21:AD:30 handle 12 state 1 lm MASTER AUTH ENCRYPT`
 * 返回 0=找到（17 字符大写冒号分隔），-1=无 ACL 连接/参数非法。 */
int bt_dev_acl_mac(const char *hcitool_con, char *mac, size_t macsz)
{
    if (!hcitool_con || !mac || macsz < 18) return -1;
    mac[0] = 0;
    const char *ln = hcitool_con;
    while (ln && *ln) {
        const char *nl = strchr(ln, '\n');
        const char *le = nl ? nl : (ln + strlen(ln));
        size_t linelen = (size_t)(le - ln);
        char line[256];
        if (linelen >= sizeof line) linelen = sizeof line - 1;
        memcpy(line, ln, linelen); line[linelen] = 0;
        if (strstr(line, "ACL")) {
            /* 行内找合法的 MAC token（6 组 2 位十六进制，冒号分隔） */
            for (const char *p = line; *p; p++) {
                int ok = 1;
                for (int i = 0; i < 17 && ok; i++) {
                    if ((i % 3) == 2) { if (p[i] != ':') ok = 0; }
                    else {
                        char c = p[i];
                        if (!((c >= '0' && c <= '9') || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f'))) ok = 0;
                    }
                }
                /* 必须是完整 token：前一个字符不是十六进制/冒号，后一个不是 */
                if (ok && (p == line || !(p[-1] == ':' || (p[-1] >= '0' && p[-1] <= '9') ||
                                          (p[-1] >= 'A' && p[-1] <= 'F') || (p[-1] >= 'a' && p[-1] <= 'f')))
                       && !(p[17] == ':' || (p[17] >= '0' && p[17] <= '9') ||
                            (p[17] >= 'A' && p[17] <= 'F') || (p[17] >= 'a' && p[17] <= 'f'))) {
                    for (int i = 0; i < 17; i++) {
                        char c = p[i];
                        mac[i] = (c >= 'a' && c <= 'f') ? (char)(c - 'a' + 'A') : c;
                    }
                    mac[17] = 0;
                    return 0;
                }
            }
        }
        if (!nl) break;
        ln = nl + 1;
    }
    return -1;
}

/* 从 D-Bus 对象路径取 MAC。bluealsa 4.1.1 的 PCM 路径是
 *   /org/bluealsa/hci0/dev_33_DE_2E_21_AD_30/a2dpsrc/sink
 * （dev_%.2X_%.2X_%.2X_%.2X_%.2X_%.2X，见 src/ba-transport.c / src/shared/dbus-client.c）。
 * 返回 0=解析出 17 字符 MAC（大写、冒号分隔）。 */
static int parse_dev_seg(const char *line, char *mac, size_t macsz)
{
    if (!line || !mac || macsz < 18) return -1;
    const char *d = strstr(line, "dev_");
    if (!d) return -1;
    const char *p = d + 4;
    char out[18];
    size_t o = 0;
    for (int i = 0; i < 6; i++) {
        unsigned v = 0;
        int digits = 0;
        for (; digits < 2; digits++) {
            char c = *p;
            int h = -1;
            if (c >= '0' && c <= '9') h = c - '0';
            else if (c >= 'A' && c <= 'F') h = c - 'A' + 10;
            else if (c >= 'a' && c <= 'f') h = c - 'a' + 10;
            if (h < 0) break;
            v = v * 16u + (unsigned)h;
            p++;
        }
        if (digits == 0) return -1;
        o += (size_t)snprintf(out + o, sizeof out - o, (i == 0) ? "%02X" : ":%02X", v);
        if (i < 5) {
            if (*p != '_') return -1;
            p++;
        }
    }
    if (o != 17) return -1;
    memcpy(mac, out, 18);
    return 0;
}

/* 兜底：端点 token 的最后一段直接是 MAC（老式/简化输出 `a2dpsrc/AA:BB:...`）。 */
static int parse_tail_mac(const char *hit, char *mac, size_t macsz)
{
    const char *te = hit;
    while (*te && *te != ' ' && *te != '\t' && *te != '\n') te++;
    const char *slash = NULL;
    for (const char *q = hit; q < te; q++) if (*q == '/') slash = q;
    if (!slash || (slash + 1) >= te) return -1;
    const char *start = slash + 1;
    size_t len = (size_t)(te - start);
    if (len != 17 || len >= macsz) return -1;
    int colons = 0;
    for (size_t i = 0; i < len; i++) if (start[i] == ':') colons++;
    if (colons != 5) return -1;
    memcpy(mac, start, len);
    mac[len] = 0;
    return 0;
}

/* 解析 bluealsa-cli list-pcms 输出，取第一个 a2dpsrc/a2dp_source 端点的设备 MAC。
 * 真实输出是 D-Bus 对象路径（每行一个）：
 *   /org/bluealsa/hci0/dev_33_DE_2E_21_AD_30/a2dpsrc/sink
 * MAC 取自 `dev_XX_XX_XX_XX_XX_XX` 段（下划线 → 冒号），另兼容简化形式 `a2dpsrc/AA:BB:...`。
 * 逐个**有界行**匹配（strstr 必须在行内，避免跨换行误把后一行当本行端点——如行 1
 * "hfphf/source" 与行 2 "a2dpsrc/sink" 的经典误判）。 */
int bt_dev_detect_mac(const char *listpcms, char *mac, size_t macsz)
{
    if (!listpcms || !mac || macsz < 2) return -1;
    mac[0] = 0;
    const char *ln = listpcms;
    while (ln && *ln) {
        const char *nl = strchr(ln, '\n');
        const char *le = nl ? nl : (ln + strlen(ln));
        size_t linelen = (size_t)(le - ln);
        char line[256];
        if (linelen >= sizeof line) linelen = sizeof line - 1;
        memcpy(line, ln, linelen); line[linelen] = 0;
        const char *p = line;
        while (*p == ' ' || *p == '\t') p++;
        if (line_is_src(line)) {
            if (parse_dev_seg(p, mac, macsz) == 0) return 0;
            const char *hit = strstr(p, "a2dpsrc");
            if (!hit) hit = strstr(p, "a2dp_source");
            if (hit && parse_tail_mac(hit, mac, macsz) == 0) return 0;
        }
        if (!nl) break;
        ln = nl + 1;
    }
    mac[0] = 0;
    return -1;
}

int bt_dev_count_src(const char *listpcms)
{
    if (!listpcms) return 0;
    int n = 0;
    const char *ln = listpcms;
    while (ln && *ln) {
        const char *nl = strchr(ln, '\n');
        if (line_is_src(ln)) n++;
        if (!nl) break;
        ln = nl + 1;
    }
    return n;
}

/* 取第一个 a2dpsrc/a2dp_source 端点的**完整 D-Bus 路径**（`bluealsa-cli volume|info` 要的就是它，
 * 不是 MAC）。行内按空白截断（含 \r，防 CRLF 把换行带进命令）；越界/无端点 → -1。 */
int bt_dev_endpoint_path(const char *listpcms, char *out, size_t outsz)
{
    if (!listpcms || !out || outsz < 2) return -1;
    out[0] = 0;
    const char *ln = listpcms;
    while (ln && *ln) {
        const char *nl = strchr(ln, '\n');
        const char *p = ln;
        while (*p == ' ' || *p == '\t') p++;
        if (line_is_src(ln)) {
            size_t n = 0;
            while (p[n] && p[n] != ' ' && p[n] != '\t' && p[n] != '\n' && p[n] != '\r' && n + 1 < outsz) {
                out[n] = p[n];
                n++;
            }
            out[n] = 0;
            return n ? 0 : -1;
        }
        if (!nl) break;
        ln = nl + 1;
    }
    return -1;
}

/* 从 `bluealsa-cli info <path>` 输出取实际协商到的 codec（"Selected codec: AAC" → "AAC"）。
 * 只认行首 "Selected codec:"（"Available codecs: SBC AAC" 那行不能误匹配）。 */
int bt_dev_info_codec(const char *info_out, char *out, size_t outsz)
{
    if (!info_out || !out || outsz < 2) return -1;
    out[0] = 0;
    const char *ln = info_out;
    while (ln && *ln) {
        const char *nl = strchr(ln, '\n');
        const char *p = ln;
        while (*p == ' ' || *p == '\t') p++;
        if (strncmp(p, "Selected codec:", 15) == 0) {
            p += 15;
            while (*p == ' ' || *p == '\t') p++;
            size_t n = 0;
            while (p[n] && p[n] != '\n' && p[n] != '\r' && n + 1 < outsz) { out[n] = p[n]; n++; }
            while (n > 0 && (out[n-1] == ' ' || out[n-1] == '\t')) n--;
            out[n] = 0;
            return n ? 0 : -1;
        }
        if (!nl) break;
        ln = nl + 1;
    }
    return -1;
}

/* bluealsa 4.1.1 src/shared/a2dp-codecs.c 的 canonical 名与别名（strcasecmp 匹配）。
 * 只列本机可达的音频 codec；auto/unchanged/未知 → unchanged（不干预协商）。 */
static const struct {
    const char *canonical;
    const char *aliases[4];
} codecs[] = {
    { "SBC",        { "SBC", NULL } },
    { "MP3",        { "MP3", "MPEG12", "MPEG", NULL } },
    { "AAC",        { "AAC", "MPEG24", NULL } },
    { "ATRAC",      { "ATRAC", NULL } },
    { "aptX",       { "aptX", "apt-X", NULL } },
    { "aptX-AD",    { "aptX-AD", "apt-X-AD", NULL } },
    { "aptX-HD",    { "aptX-HD", "apt-X-HD", NULL } },
    { "aptX-LL",    { "aptX-LL", "apt-X-LL", NULL } },
    { "aptX-TWS",   { "aptX-TWS", "apt-X-TWS", NULL } },
    { "FastStream", { "FastStream", "FS", NULL } },
    { "LC3plus",    { "LC3plus", NULL } },
    { "LDAC",       { "LDAC", NULL } },
    { "LHDC",       { "LHDC", NULL } },
};

const char *bt_dev_codec_token(const char *setting, char *out, size_t outsz)
{
    const char *auto_tok = "unchanged";
    if (!out || outsz < 2) return auto_tok;
    if (!setting || !setting[0]) { snprintf(out, outsz, "%s", auto_tok); return out; }
    if (!strcasecmp(setting, "auto") || !strcasecmp(setting, "unchanged")) {
        snprintf(out, outsz, "%s", auto_tok);
        return out;
    }
    for (size_t i = 0; i < sizeof codecs / sizeof codecs[0]; i++)
        for (size_t n = 0; n < 4 && codecs[i].aliases[n]; n++)
            if (!strcasecmp(codecs[i].aliases[n], setting)) {
                snprintf(out, outsz, "%s", codecs[i].canonical);
                return out;
            }
    snprintf(out, outsz, "%s", auto_tok);   /* 未知值：不干预协商（不把垃圾塞进 PCM 名） */
    return out;
}

/* MAC 合法性：6 组两位十六进制，'/' 或 ':' 分隔都不接受（只认冒号，bluealsa 约定）。 */
static int mac_valid(const char *mac)
{
    if (!mac || strlen(mac) != 17) return 0;
    for (int i = 0; i < 17; i++) {
        if ((i % 3) == 2) { if (mac[i] != ':') return 0; }
        else {
            char c = mac[i];
            int hex = (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F');
            if (!hex) return 0;
        }
    }
    return 1;
}

int bt_dev_pcm_name(const char *mac, const char *codec_token, char *out, size_t outsz)
{
    if (!out || outsz < 32 || !mac_valid(mac)) return -1;
    const char *tok = (codec_token && codec_token[0]) ? codec_token : "unchanged";
    int n = snprintf(out, outsz, "bluealsa:DEV=%s,PROFILE=a2dp,CODEC=%s", mac, tok);
    if (n < 0 || (size_t)n >= outsz) { out[0] = 0; return -1; }
    return 0;
}

unsigned bt_dev_backoff_ms(unsigned fails)
{
    if (fails == 0) return 0;
    unsigned shift = fails - 1;
    if (shift > 5) shift = 5;
    unsigned long d = 2000UL << shift;      /* 2s,4s,8s,16s,32s,64s */
    if (d > 60000UL) d = 60000UL;
    return (unsigned)d;
}

int bt_dev_should_try(unsigned fails, long long since_ms)
{
    if (fails == 0) return 1;
    if (since_ms < 0) return 1;
    return since_ms >= (long long)bt_dev_backoff_ms(fails) ? 1 : 0;
}