/* bt_dev.c — 蓝牙 A2DP 设备自识别（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
 * 读取 /usr/data/alsa.conf、执行 `bluealsa-cli list-pcms` 及写回。宿主单测零链路重。
 */
#include "bt_dev.h"

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

/* 解析 bluealsa-cli list-pcms 输出，取第一个 a2dpsrc/a2dp_source 端点的设备 MAC。
 * 端点形如 `a2dpsrc/AA:BB:CC:DD:EE:FF`（MAC 在端点 token 内最后一个 '/' 之后到空白前）。
 * 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
 * "profile/aptx" 与行 3 "a2dp_source/..." 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++;
        const char *hit = strstr(p, "a2dpsrc");
        if (!hit) hit = strstr(p, "a2dp_source");
        if (hit) {
            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) {
                const char *start = slash + 1;
                size_t len = (size_t)(te - start);
                if (len > 0 && len < macsz) {
                    memcpy(mac, start, len);
                    mac[len] = 0;
                    return 0;
                }
            }
        }
        if (!nl) break;
        ln = nl + 1;
    }
    return -1;
}

/* 在单行内把 anchor（"DEV=" / "device"）后的 MAC 值替换为 mac，保留引号风格。
 * 行未含 anchor → 返回 1（out=原样）；含 anchor → 写回新行并返回 0。 */
static int line_replace_mac(char *out, size_t outsz, const char *line,
                            const char *anchor, const char *mac)
{
    const char *at = strstr(line, anchor);
    if (!at) { snprintf(out, outsz, "%s", line); return 1; }
    const char *vp = at + strlen(anchor);
    while (*vp == ' ' || *vp == '\t') vp++;
    if (*vp == '"') vp++;                       /* 引号风格：值可带双引号 */
    const char *ve = vp;
    while (*ve && *ve != ' ' && *ve != '\t' && *ve != '\n' &&
           *ve != '"' && *ve != '{' && *ve != '}') ve++;
    size_t prefix = (size_t)(vp - line);        /* 前段（含开引号，若带） */
    size_t tail   = (size_t)(ve - line);        /* 值终点（不含闭引号，若带） */
    /* 前段 + mac + 尾段（尾段保留闭引号与其后内容） */
    snprintf(out, outsz, "%.*s%s%s", (int)prefix, line, mac, line + tail);
    return 0;
}

/* 幂等改写 alsa.conf：只把 `pcm.bluealsa` 块内 `DEV=` 与 `device` 后的 MAC 换成 mac。
 * 逐行处理；无 pcm.bluealsa / 无 DEV= / device token → -1；两端已一致 → 1；改了 → 0。 */
int bt_dev_rewrite(const char *in, size_t in_len, const char *mac,
                   char **out, size_t *out_len)
{
    if (!in || !mac || !mac[0] || !out || !out_len || in_len == 0) return -1;
    if (!strstr(in, "pcm.bluealsa") ||
        (!strstr(in, "DEV=") && !strstr(in, "device"))) return -1;

    size_t cap = in_len + 128;
    char *res = malloc(cap ? cap : 1);
    if (!res) return -1;
    size_t o = 0, changed = 0;
    const char *p = in, *end = in + in_len;

    while (p < end) {
        const char *nl = memchr(p, '\n', (size_t)(end - p));
        const char *le = nl ? nl : end;
        size_t linelen = (size_t)(le - p);
        char line[512], newline[512];
        if (linelen >= sizeof line) linelen = sizeof line - 1;
        memcpy(line, p, linelen); line[linelen] = 0;

        const char *k = line;
        while (*k == ' ' || *k == '\t') k++;
        int anchored = 0;
        if (strstr(k, "DEV=")) {
            line_replace_mac(newline, sizeof newline, line, "DEV=", mac);
            anchored = 1;
        } else if (strncmp(k, "device", 6) == 0 &&
                   (k[6] == ' ' || k[6] == '\t' || k[6] == 0)) {
            line_replace_mac(newline, sizeof newline, line, "device", mac);
            anchored = 1;
        }
        if (anchored) {
            if (strcmp(line, newline) != 0) changed = 1;
            size_t n = strlen(newline);
            if (o + n + 2 > cap) {
                cap = o + n + 256;
                char *t = realloc(res, cap);
                if (!t) { free(res); return -1; }
                res = t;
            }
            memcpy(res + o, newline, n); o += n;
            if (nl) res[o++] = '\n';
        } else {
            size_t n = linelen;
            if (o + n + 2 > cap) {
                cap = o + n + 256;
                char *t = realloc(res, cap);
                if (!t) { free(res); return -1; }
                res = t;
            }
            memcpy(res + o, p, n); o += n;
            if (nl) res[o++] = '\n';
        }
        if (!nl) break;
        p = nl + 1;
    }

    if (!changed) { free(res); return 1; }
    res[o] = 0;
    *out = res;
    *out_len = o;
    return 0;
}