// SPDX-License-Identifier: GPL-2.0
//
// Copyright (C) 2018 Masahiro Yamada <yamada.masahiro@socionext.com>

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

#include <array_size.h>
#include <list.h>
#include <xalloc.h>
#include "internal.h"
#include "lkc.h"
#include "preprocess.h"

static char *expand_string_with_args(const char *in, int argc, char *argv[]);
static char *expand_string(const char *in);

static void __attribute__((noreturn)) pperror(const char *format, ...)
{
        va_list ap;

        fprintf(stderr, "%s:%d: ", cur_filename, yylineno);
        va_start(ap, format);
        vfprintf(stderr, format, ap);
        va_end(ap);
        fprintf(stderr, "\n");

        exit(1);
}

/*
 * Environment variables
 */
static LIST_HEAD(env_list);

struct env {
        char *name;
        char *value;
        struct list_head node;
};

static void env_add(const char *name, const char *value)
{
        struct env *e;

        e = xmalloc(sizeof(*e));
        e->name = xstrdup(name);
        e->value = xstrdup(value);

        list_add_tail(&e->node, &env_list);
}

static void env_del(struct env *e)
{
        list_del(&e->node);
        free(e->name);
        free(e->value);
        free(e);
}

/* The returned pointer must be freed when done */
static char *env_expand(const char *name)
{
        struct env *e;
        const char *value;

        if (!*name)
                return NULL;

        list_for_each_entry(e, &env_list, node) {
                if (!strcmp(name, e->name))
                        return xstrdup(e->value);
        }

        value = getenv(name);
        if (!value)
                return NULL;

        /*
         * We need to remember all referenced environment variables.
         * They will be written out to include/config/auto.conf.cmd
         */
        env_add(name, value);

        return xstrdup(value);
}

void env_write_dep(struct gstr *s)
{
        struct env *e, *tmp;

        list_for_each_entry_safe(e, tmp, &env_list, node) {
                str_printf(s,
                           "\n"
                           "ifneq \"$(%s)\" \"%s\"\n"
                           "$(autoconfig): FORCE\n"
                           "endif\n",
                           e->name, e->value);
                env_del(e);
        }
}

/*
 * Built-in functions
 */
struct function {
        const char *name;
        unsigned int min_args;
        unsigned int max_args;
        char *(*func)(int argc, char *argv[]);
};

static char *do_error_if(int argc, char *argv[])
{
        if (!strcmp(argv[0], "y"))
                pperror("%s", argv[1]);

        return xstrdup("");
}

static char *do_filename(int argc, char *argv[])
{
        return xstrdup(cur_filename);
}

static char *do_info(int argc, char *argv[])
{
        printf("%s\n", argv[0]);

        return xstrdup("");
}

static char *do_lineno(int argc, char *argv[])
{
        char buf[16];

        sprintf(buf, "%d", yylineno);

        return xstrdup(buf);
}

static char *do_shell(int argc, char *argv[])
{
        FILE *p;
        char buf[4096];
        char *cmd;
        size_t nread;
        int i;

        cmd = argv[0];

        p = popen(cmd, "r");
        if (!p) {
                perror(cmd);
                exit(1);
        }

        nread = fread(buf, 1, sizeof(buf), p);
        if (nread == sizeof(buf))
                nread--;

        /* remove trailing new lines */
        while (nread > 0 && buf[nread - 1] == '\n')
                nread--;

        buf[nread] = 0;

        /* replace a new line with a space */
        for (i = 0; i < nread; i++) {
                if (buf[i] == '\n')
                        buf[i] = ' ';
        }

        if (pclose(p) == -1) {
                perror(cmd);
                exit(1);
        }

        return xstrdup(buf);
}

static char *do_warning_if(int argc, char *argv[])
{
        if (!strcmp(argv[0], "y"))
                fprintf(stderr, "%s:%d: %s\n", cur_filename, yylineno, argv[1]);

        return xstrdup("");
}

static const struct function function_table[] = {
        /* Name         MIN     MAX     Function */
        { "error-if",   2,      2,      do_error_if },
        { "filename",   0,      0,      do_filename },
        { "info",       1,      1,      do_info },
        { "lineno",     0,      0,      do_lineno },
        { "shell",      1,      1,      do_shell },
        { "warning-if", 2,      2,      do_warning_if },
};

#define FUNCTION_MAX_ARGS               16

static char *function_expand(const char *name, int argc, char *argv[])
{
        const struct function *f;
        int i;

        for (i = 0; i < ARRAY_SIZE(function_table); i++) {
                f = &function_table[i];
                if (strcmp(f->name, name))
                        continue;

                if (argc < f->min_args)
                        pperror("too few function arguments passed to '%s'",
                                name);

                if (argc > f->max_args)
                        pperror("too many function arguments passed to '%s'",
                                name);

                return f->func(argc, argv);
        }

        return NULL;
}

/*
 * Variables (and user-defined functions)
 */
static LIST_HEAD(variable_list);

struct variable {
        char *name;
        char *value;
        enum variable_flavor flavor;
        int exp_count;
        struct list_head node;
};

static struct variable *variable_lookup(const char *name)
{
        struct variable *v;

        list_for_each_entry(v, &variable_list, node) {
                if (!strcmp(name, v->name))
                        return v;
        }

        return NULL;
}

static char *variable_expand(const char *name, int argc, char *argv[])
{
        struct variable *v;
        char *res;

        v = variable_lookup(name);
        if (!v)
                return NULL;

        if (argc == 0 && v->exp_count)
                pperror("Recursive variable '%s' references itself (eventually)",
                        name);

        if (v->exp_count > 1000)
                pperror("Too deep recursive expansion");

        v->exp_count++;

        if (v->flavor == VAR_RECURSIVE)
                res = expand_string_with_args(v->value, argc, argv);
        else
                res = xstrdup(v->value);

        v->exp_count--;

        return res;
}

void variable_add(const char *name, const char *value,
                  enum variable_flavor flavor)
{
        struct variable *v;
        char *new_value;
        bool append = false;

        v = variable_lookup(name);
        if (v) {
                /* For defined variables, += inherits the existing flavor */
                if (flavor == VAR_APPEND) {
                        flavor = v->flavor;
                        append = true;
                } else {
                        free(v->value);
                }
        } else {
                /* For undefined variables, += assumes the recursive flavor */
                if (flavor == VAR_APPEND)
                        flavor = VAR_RECURSIVE;

                v = xmalloc(sizeof(*v));
                v->name = xstrdup(name);
                v->exp_count = 0;
                list_add_tail(&v->node, &variable_list);
        }

        v->flavor = flavor;

        if (flavor == VAR_SIMPLE)
                new_value = expand_string(value);
        else
                new_value = xstrdup(value);

        if (append) {
                v->value = xrealloc(v->value,
                                    strlen(v->value) + strlen(new_value) + 2);
                strcat(v->value, " ");
                strcat(v->value, new_value);
                free(new_value);
        } else {
                v->value = new_value;
        }
}

static void variable_del(struct variable *v)
{
        list_del(&v->node);
        free(v->name);
        free(v->value);
        free(v);
}

void variable_all_del(void)
{
        struct variable *v, *tmp;

        list_for_each_entry_safe(v, tmp, &variable_list, node)
                variable_del(v);
}

/*
 * Evaluate a clause with arguments.  argc/argv are arguments from the upper
 * function call.
 *
 * Returned string must be freed when done
 */
static char *eval_clause(const char *str, size_t len, int argc, char *argv[])
{
        char *tmp, *name, *res, *endptr, *prev, *p;
        int new_argc = 0;
        char *new_argv[FUNCTION_MAX_ARGS];
        int nest = 0;
        int i;
        unsigned long n;

        tmp = xstrndup(str, len);

        /*
         * If variable name is '1', '2', etc.  It is generally an argument
         * from a user-function call (i.e. local-scope variable).  If not
         * available, then look-up global-scope variables.
         */
        n = strtoul(tmp, &endptr, 10);
        if (!*endptr && n > 0 && n <= argc) {
                res = xstrdup(argv[n - 1]);
                goto free_tmp;
        }

        prev = p = tmp;

        /*
         * Split into tokens
         * The function name and arguments are separated by a comma.
         * For example, if the function call is like this:
         *   $(foo,$(x),$(y))
         *
         * The input string for this helper should be:
         *   foo,$(x),$(y)
         *
         * and split into:
         *   new_argv[0] = 'foo'
         *   new_argv[1] = '$(x)'
         *   new_argv[2] = '$(y)'
         */
        while (*p) {
                if (nest == 0 && *p == ',') {
                        *p = 0;
                        if (new_argc >= FUNCTION_MAX_ARGS)
                                pperror("too many function arguments");
                        new_argv[new_argc++] = prev;
                        prev = p + 1;
                } else if (*p == '(') {
                        nest++;
                } else if (*p == ')') {
                        nest--;
                }

                p++;
        }

        if (new_argc >= FUNCTION_MAX_ARGS)
                pperror("too many function arguments");
        new_argv[new_argc++] = prev;

        /*
         * Shift arguments
         * new_argv[0] represents a function name or a variable name.  Put it
         * into 'name', then shift the rest of the arguments.  This simplifies
         * 'const' handling.
         */
        name = expand_string_with_args(new_argv[0], argc, argv);
        new_argc--;
        for (i = 0; i < new_argc; i++)
                new_argv[i] = expand_string_with_args(new_argv[i + 1],
                                                      argc, argv);

        /* Search for variables */
        res = variable_expand(name, new_argc, new_argv);
        if (res)
                goto free;

        /* Look for built-in functions */
        res = function_expand(name, new_argc, new_argv);
        if (res)
                goto free;

        /* Last, try environment variable */
        if (new_argc == 0) {
                res = env_expand(name);
                if (res)
                        goto free;
        }

        res = xstrdup("");
free:
        for (i = 0; i < new_argc; i++)
                free(new_argv[i]);
        free(name);
free_tmp:
        free(tmp);

        return res;
}

/*
 * Expand a string that follows '$'
 *
 * For example, if the input string is
 *     ($(FOO)$($(BAR)))$(BAZ)
 * this helper evaluates
 *     $($(FOO)$($(BAR)))
 * and returns a new string containing the expansion (note that the string is
 * recursively expanded), also advancing 'str' to point to the next character
 * after the corresponding closing parenthesis, in this case, *str will be
 *     $(BAR)
 */
static char *expand_dollar_with_args(const char **str, int argc, char *argv[])
{
        const char *p = *str;
        const char *q;
        int nest = 0;

        /*
         * In Kconfig, variable/function references always start with "$(".
         * Neither single-letter variables as in $A nor curly braces as in ${CC}
         * are supported.  '$' not followed by '(' loses its special meaning.
         */
        if (*p != '(') {
                *str = p;
                return xstrdup("$");
        }

        p++;
        q = p;
        while (*q) {
                if (*q == '(') {
                        nest++;
                } else if (*q == ')') {
                        if (nest-- == 0)
                                break;
                }
                q++;
        }

        if (!*q)
                pperror("unterminated reference to '%s': missing ')'", p);

        /* Advance 'str' to after the expanded initial portion of the string */
        *str = q + 1;

        return eval_clause(p, q - p, argc, argv);
}

char *expand_dollar(const char **str)
{
        return expand_dollar_with_args(str, 0, NULL);
}

static char *__expand_string(const char **str, bool (*is_end)(char c),
                             int argc, char *argv[])
{
        const char *in, *p;
        char *expansion, *out;
        size_t in_len, out_len;

        out = xmalloc(1);
        *out = 0;
        out_len = 1;

        p = in = *str;

        while (1) {
                if (*p == '$') {
                        in_len = p - in;
                        p++;
                        expansion = expand_dollar_with_args(&p, argc, argv);
                        out_len += in_len + strlen(expansion);
                        out = xrealloc(out, out_len);
                        strncat(out, in, in_len);
                        strcat(out, expansion);
                        free(expansion);
                        in = p;
                        continue;
                }

                if (is_end(*p))
                        break;

                p++;
        }

        in_len = p - in;
        out_len += in_len;
        out = xrealloc(out, out_len);
        strncat(out, in, in_len);

        /* Advance 'str' to the end character */
        *str = p;

        return out;
}

static bool is_end_of_str(char c)
{
        return !c;
}

/*
 * Expand variables and functions in the given string.  Undefined variables
 * expand to an empty string.
 * The returned string must be freed when done.
 */
static char *expand_string_with_args(const char *in, int argc, char *argv[])
{
        return __expand_string(&in, is_end_of_str, argc, argv);
}

static char *expand_string(const char *in)
{
        return expand_string_with_args(in, 0, NULL);
}

static bool is_end_of_token(char c)
{
        return !(isalnum(c) || c == '_' || c == '-');
}

/*
 * Expand variables in a token.  The parsing stops when a token separater
 * (in most cases, it is a whitespace) is encountered.  'str' is updated to
 * point to the next character.
 *
 * The returned string must be freed when done.
 */
char *expand_one_token(const char **str)
{
        return __expand_string(str, is_end_of_token, 0, NULL);
}