/*
 * log.h
 *
 * Copyright (c) 2026 Eric Vidal <eric@obarun.org>
 *
 * All rights reserved.
 *
 * This file is part of Obarun. It is subject to the license terms in
 * the LICENSE file found in the top-level directory of this
 * distribution.
 * This file may not be copied, modified, propagated, or distributed
 * except according to the terms contained in the LICENSE file.
 */

#ifndef SS_LOG_H
#define SS_LOG_H

#include <sys/types.h>
#include <time.h>
#include <stdint.h>
#include <regex.h>

#include <oblibs/strbuf.h>

#include <66/config.h>

/** Kind of timestamp prefix found at the head of a log line. */
#define LOG_STAMP_NONE   0
#define LOG_STAMP_TAI64N 1
#define LOG_STAMP_ISO    2

typedef struct log_line_s log_line_t, *log_line_t_ref ;
struct log_line_s {
    struct timespec stamp ; // time key as Unix UTC epoch (inherited for unstamped lines)
    size_t off ;            // line start offset in the owning source buffer
    size_t len ;            // line length, trailing newline excluded
    size_t msgoff ;         // offset within the line to the message (past the stamp)
    uint8_t type ;          // LOG_STAMP_*
} ;

typedef struct log_source_s log_source_t, *log_source_t_ref ;
struct log_source_s {
    char name[SS_MAX_SERVICE_NAME + 1] ; // service name, or "system" (bounded, no alloc)
    strbuf data ;           // owned, concatenated raw content of every file
    log_line_t *line ;      // owned array of parsed lines
    size_t nline ;
    size_t cur ;            // merge cursor
    uint8_t stamped ;       // 1 if at least one line carried a stamp
} ;

#define LOG_SOURCE_ZERO { .data = STRBUF_ZERO, .line = 0, .nline = 0, .cur = 0, .stamped = 0 }

/**
 * @brief Parse a "YYYY-MM-DD[<sep>HH:MM:SS[.frac]]" local-time prefix (<sep> is a
 *        space, 'T' or 't') via a table-driven DFA.
 * @param[in] s    Bytes to scan.
 * @param[in] len  Length of @s.
 * @param[out] ts  Receives the decoded local time (Unix UTC epoch + nanoseconds).
 * @param[out] end Receives the offset just past the matched timestamp (longest match).
 * @return 1 if a valid date or datetime prefix was parsed (fields range-checked).
 * @return 0 otherwise (nothing written).
 */
extern int log_iso_scan(char const *s, size_t len, struct timespec *ts, size_t *end) ;

/**
 * @brief Detect and parse the leading timestamp of a log line.
 * @param[in] line   Line bytes (newline excluded), not NUL-terminated.
 * @param[in] len    Line length.
 * @param[out] ts    Receives the decoded time key (untouched for LOG_STAMP_NONE).
 * @param[out] msgoff Receives the offset to the message (past stamp+spaces); 0 for NONE.
 * @return LOG_STAMP_TAI64N, LOG_STAMP_ISO, or LOG_STAMP_NONE.
 */
extern int log_line_key(char const *line, size_t len, struct timespec *ts, size_t *msgoff) ;

/**
 * @brief Load a 66-log logdir into @src: concatenate the rotated archives
 *        (`@<tai64n>.{s,u}`, name-sorted ascending) then `current`, and parse the
 *        result into time-keyed lines. @name is copied (owned).
 * @return 1 on success.
 * @return 0 on system error (errno preserved).
 */
extern int log_source_logdir(log_source_t *src, char const *name, char const *logdir) ;

/**
 * @brief Load a single plain log file into @src and parse it. @name is copied.
 * @return 1 on success.
 * @return 0 on system error (errno preserved).
 */
extern int log_source_file(log_source_t *src, char const *name, char const *file) ;

/** @brief Release every buffer owned by @src and zero it. */
extern void log_source_free(log_source_t *src) ;

/**
 * @brief Emit one parsed log line to stdout (ostream_1): the timestamp (TAI64N
 *        reformatted to local time, otherwise the line's own leading stamp kept
 *        verbatim), an optional "name: " tag placed right after the timestamp
 *        (syslog-style), then the message and a newline. Does not flush.
 * @param[in] line     Line bytes (newline excluded).
 * @param[in] len      Line length.
 * @param[in] msgoff   Offset of the message within @line (0 for an unstamped line).
 * @param[in] type     LOG_STAMP_* of the line.
 * @param[in] stamp    Decoded time key (used only for LOG_STAMP_TAI64N).
 * @param[in] name     Source name for the tag.
 * @param[in] withname 1 to emit the "name: " tag, 0 to omit it.
 * @note Dies (LOG_EXIT_SYS) on a write error.
 */
extern void log_emit(char const *line, size_t len, size_t msgoff, uint8_t type, struct timespec const *stamp, char const *name, uint8_t withname) ;

/**
 * @brief Follow a single log source in real time (tail -f), emitting only the
 *        lines appended after the call. Blocks in an event loop until SIGINT or
 *        SIGTERM. For a 66-log logdir it also follows the rotation of `current`.
 * @param[in] name      Source name for the tag ("system" or a service name).
 * @param[in] path      The logdir (when @is_logdir) or the plain file to follow.
 * @param[in] is_logdir 1 for a 66-log logdir, 0 for a plain file.
 * @param[in] withname  1 to tag each line with @name, 0 otherwise.
 * @param[in] re        POSIX extended regex to filter lines, or 0 for no filter.
 * @return 1 on clean exit (signal received).
 * @return 0 on system error (errno set).
 */
extern int log_follow(char const *name, char const *path, uint8_t is_logdir, uint8_t withname, regex_t *re) ;

#endif