#include "git/git_context.h"

#include "git/git_command.h"

#include "foundation/compat.h"
#include "foundation/platform.h"
#include "foundation/str_util.h"

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

static bool path_is_absolute(const char *path) {
    if (!path || !path[0]) {
        return false;
    }
    if (path[0] == '/') {
        return true;
    }
#ifdef _WIN32
    return isalpha((unsigned char)path[0]) && path[1] == ':';
#else
    return false;
#endif
}

static char *join_root_relative(const char *root, const char *rel) {
    if (!root || !root[0]) {
        return cbm_strdup(rel);
    }
    int n = snprintf(NULL, 0, "%s/%s", root, rel);
    if (n < 0) {
        return NULL;
    }
    char *out = (char *)malloc((size_t)n + 1);
    if (!out) {
        return NULL;
    }
    snprintf(out, (size_t)n + 1, "%s/%s", root, rel);
    return out;
}

static char *derive_canonical_root(const char *worktree_root, const char *git_common_dir) {
    const char *src = git_common_dir && git_common_dir[0] ? git_common_dir : worktree_root;
    if (!src) {
        return cbm_strdup("");
    }

    char *root = path_is_absolute(src) ? cbm_strdup(src) : join_root_relative(worktree_root, src);
    if (!root) {
        return NULL;
    }

    size_t len = strlen(root);
    while (len > 1 && (root[len - 1] == '/' || root[len - 1] == '\\')) {
        root[--len] = '\0';
    }

    if (len >= 5 && strcmp(root + len - 5, "/.git") == 0) {
        root[len - 5] = '\0';
    }
#ifdef _WIN32
    else if (len >= 5 && strcmp(root + len - 5, "\\.git") == 0) {
        root[len - 5] = '\0';
    }
#endif

    return root;
}

static char *slug_from_branch(const char *branch, bool detached) {
    const char *fallback = detached ? "detached" : "working-tree";
    const char *src = detached ? fallback : (branch && branch[0] ? branch : fallback);
    size_t len = strlen(src);
    char *slug = (char *)malloc(len + 1);
    if (!slug) {
        return NULL;
    }

    size_t j = 0;
    bool in_dash = false;
    for (size_t i = 0; i < len; i++) {
        unsigned char c = (unsigned char)src[i];
        if (isalnum(c) || c == '-' || c == '_' || c == '.') {
            if (j == 0 && c == '-') {
                in_dash = true;
                continue;
            }
            slug[j++] = (char)c;
            in_dash = false;
        } else if (j > 0 && !in_dash) {
            slug[j++] = '-';
            in_dash = true;
        }
    }
    while (j > 0 && slug[j - 1] == '-') {
        j--;
    }
    slug[j] = '\0';

    if (slug[0] == '\0') {
        free(slug);
        return cbm_strdup(fallback);
    }
    return slug;
}

void cbm_git_context_free(cbm_git_context_t *ctx) {
    if (!ctx) {
        return;
    }
    free(ctx->input_path);
    free(ctx->worktree_root);
    free(ctx->git_dir);
    free(ctx->git_common_dir);
    free(ctx->canonical_root);
    free(ctx->branch);
    free(ctx->branch_slug);
    free(ctx->head_sha);
    free(ctx->base_sha);
    memset(ctx, 0, sizeof(*ctx));
}

int cbm_git_context_resolve(const char *path, cbm_git_context_t *out) {
    if (!out) {
        return CBM_NOT_FOUND;
    }

    memset(out, 0, sizeof(*out));
    if (!path || !path[0]) {
        return CBM_NOT_FOUND;
    }

    out->input_path = cbm_strdup(path);
    if (!out->input_path) {
        return CBM_NOT_FOUND;
    }

    out->root_exists = cbm_file_exists(path);
    if (!out->root_exists) {
        return 0;
    }

    if (cbm_git_capture_first_line(path, "rev-parse --show-toplevel", &out->worktree_root) !=
        0) {
        out->is_git = false;
        return 0;
    }
    out->is_git = true;

    if (cbm_git_capture_first_line(path, "rev-parse --git-dir", &out->git_dir) != 0) {
        out->git_dir = cbm_strdup("");
    }
    if (cbm_git_capture_first_line(path, "rev-parse --git-common-dir", &out->git_common_dir) !=
        0) {
        out->git_common_dir = cbm_strdup("");
    }
    if (cbm_git_capture_first_line(path, "rev-parse --verify HEAD", &out->head_sha) != 0) {
        out->head_sha = cbm_strdup("");
    }

    if (cbm_git_capture_first_line(path, "symbolic-ref --quiet --short HEAD", &out->branch) !=
        0) {
        out->branch = cbm_strdup("DETACHED");
        out->is_detached = true;
    }

    out->is_worktree =
        out->git_dir && out->git_common_dir && strcmp(out->git_dir, out->git_common_dir) != 0;
    out->canonical_root = derive_canonical_root(out->worktree_root, out->git_common_dir);
    out->branch_slug = slug_from_branch(out->branch, out->is_detached);
    if (cbm_git_capture_first_line(path, "merge-base HEAD @{upstream}", &out->base_sha) != 0) {
        out->base_sha = cbm_strdup("");
    }

    if (!out->git_dir || !out->git_common_dir || !out->head_sha || !out->branch ||
        !out->canonical_root || !out->branch_slug || !out->base_sha) {
        cbm_git_context_free(out);
        return CBM_NOT_FOUND;
    }

    return 0;
}

char *cbm_git_context_branch_qn(const char *project_name, const cbm_git_context_t *ctx) {
    const char *project = project_name && project_name[0] ? project_name : "project";
    const char *slug = "working-tree";
    if (ctx) {
        if (ctx->is_detached) {
            slug = "detached";
        } else if (ctx->is_git && ctx->branch_slug && ctx->branch_slug[0]) {
            slug = ctx->branch_slug;
        }
    }

    int n = snprintf(NULL, 0, "%s.__branch__.%s", project, slug);
    if (n < 0) {
        return NULL;
    }
    char *out = (char *)malloc((size_t)n + 1);
    if (!out) {
        return NULL;
    }
    snprintf(out, (size_t)n + 1, "%s.__branch__.%s", project, slug);
    return out;
}

static bool append_fmt_checked(char *buf, int buf_size, int *off, const char *fmt, ...) {
    if (!buf || !off || buf_size <= 0 || *off < 0 || *off >= buf_size) {
        return false;
    }

    va_list ap;
    va_start(ap, fmt);
    int n = vsnprintf(buf + *off, (size_t)(buf_size - *off), fmt, ap);
    va_end(ap);
    if (n < 0 || n >= buf_size - *off) {
        buf[buf_size - 1] = '\0';
        return false;
    }
    *off += n;
    return true;
}

static int json_escaped_len(const char *src) {
    if (!src) {
        return 0;
    }
    int len = 0;
    for (int i = 0; src[i]; i++) {
        unsigned char c = (unsigned char)src[i];
        if (c == '"' || c == '\\' || c == '\n' || c == '\r' || c == '\t') {
            len += 2;
        } else if (c < 0x20) {
            continue;
        } else {
            len++;
        }
    }
    return len;
}

static bool json_append_bool(char *buf, int buf_size, int *off, const char *name, bool value,
                             bool comma) {
    return append_fmt_checked(buf, buf_size, off, "\"%s\":%s%s", name, value ? "true" : "false",
                              comma ? "," : "");
}

static bool json_append_string(char *buf, int buf_size, int *off, const char *name,
                               const char *value, bool comma) {
    int needed = json_escaped_len(value ? value : "");
    char *escaped = malloc((size_t)needed + 1);
    if (!escaped) {
        return false;
    }
    int actual = cbm_json_escape(escaped, needed + 1, value ? value : "");
    bool ok = actual == needed && append_fmt_checked(buf, buf_size, off, "\"%s\":\"%s\"%s", name,
                                                     escaped, comma ? "," : "");
    free(escaped);
    return ok;
}

int cbm_git_context_props_json(const cbm_git_context_t *ctx, char *buf, int buf_size) {
    if (!ctx || !buf || buf_size <= 0) {
        return 0;
    }

    int off = 0;
    bool ok =
        append_fmt_checked(buf, buf_size, &off, "{") &&
        json_append_bool(buf, buf_size, &off, "is_git", ctx->is_git, true) &&
        json_append_bool(buf, buf_size, &off, "is_worktree", ctx->is_worktree, true) &&
        json_append_bool(buf, buf_size, &off, "is_detached", ctx->is_detached, true) &&
        json_append_bool(buf, buf_size, &off, "root_exists", ctx->root_exists, true) &&
        json_append_string(buf, buf_size, &off, "canonical_root", ctx->canonical_root, true) &&
        json_append_string(buf, buf_size, &off, "worktree_root", ctx->worktree_root, true) &&
        json_append_string(buf, buf_size, &off, "git_common_dir", ctx->git_common_dir, true) &&
        json_append_string(buf, buf_size, &off, "branch", ctx->branch, true) &&
        json_append_string(buf, buf_size, &off, "head_sha", ctx->head_sha, true) &&
        json_append_string(buf, buf_size, &off, "base_sha", ctx->base_sha, false) &&
        append_fmt_checked(buf, buf_size, &off, "}");
    if (!ok) {
        if (buf_size > 0) {
            buf[0] = '\0';
        }
        return 0;
    }
    return off;
}