json/json.c

#include "json.h"

#include <assert.h>

#define UNREACHABLE() assert(false)

Json json_init(FILE* stream, Whitespace whitespace)
{
    return (Json){
        .stream = stream,
        .whitespace = whitespace,
        .indent_level = 0,
        .next_punctuation = BEGINNING,
    };
}

void json_free(Json* json)
{
    // `json_free` just exists for symmetry with `json_init`.
    // It does nothing, for now.
}

void begin_value(Json* json);
void end_value(Json* json);
void push_indentation(Json* json);
void pop_indentation(Json* json);
void indent(Json* json);

/// Begin a JSON array value.
void json_begin_array(Json* json)
{
    begin_value(json);
    putc('[', json->stream);
    push_indentation(json);
    json->next_punctuation = NONE;
}

/// End a JSON array value.
void json_end_array(Json* json)
{
    pop_indentation(json);
    switch (json->next_punctuation) {
    case NONE:
        break;
    case COMMA:
        indent(json);
        break;
    case BEGINNING:
    case COLON:
        // The only way to get here is by either:
        // - calling `json_end_array` right after `json_init`
        // - calling `json_end_array` right after `json_add_object_field`
        // - setting `next_punctuation` explicitly
        UNREACHABLE();
    }
    putc(']', json->stream);
    end_value(json);
}

/// Begin a JSON object value.
void json_begin_object(Json* json)
{
    begin_value(json);
    putc('{', json->stream);
    push_indentation(json);
    json->next_punctuation = NONE;
}

/// End a JSON object value.
void json_end_object(Json* json)
{
    pop_indentation(json);
    switch (json->next_punctuation) {
    case NONE:
        break;
    case COMMA:
        indent(json);
        break;
    case BEGINNING:
    case COLON:
        // The only way to get here is by either:
        // - calling `json_end_object` right after `json_init`
        // - calling `json_end_object` right after `json_add_object_field`
        // - settings `next_punctuation` explicitly
        UNREACHABLE();
    }
    putc('}', json->stream);
    end_value(json);
}

/// Add a JSON object field key.
/// This should always be followed by adding a JSON value.
void json_add_object_field(Json* json, const char* key)
{
    begin_value(json);
    fprintf(json->stream, "\"%s\"", key);
    json->next_punctuation = COLON;
}

/// Add a JSON string value.
void json_add_string(Json* json, const char* value)
{
    begin_value(json);
    fprintf(json->stream, "\"%s\"", value);
    end_value(json);
}

/// Add a JSON long value.
void json_add_long(Json* json, long value)
{
    begin_value(json);
    fprintf(json->stream, "%ld", value);
    end_value(json);
}

/// Add a JSON double value.
void json_add_double(Json* json, double value)
{
    begin_value(json);
    fprintf(json->stream, "%g", value);
    end_value(json);
}

/// Add a JSON bool value.
void json_add_bool(Json* json, bool value)
{
    begin_value(json);
    const char* s;
    if (value) {
        s = "true";
    } else {
        s = "false";
    }
    fputs(s, json->stream);
    end_value(json);
}

/// Add a JSON null value
void json_add_null(Json* json)
{
    begin_value(json);
    fputs("null", json->stream);
    end_value(json);
}

/// Begin a new JSON value.
/// Appends the appropriate punctuation to the stream.
void begin_value(Json* json)
{
    switch (json->next_punctuation) {
    case BEGINNING:
        break;
    case NONE:
        indent(json);
        break;
    case COMMA:
        fputc(',', json->stream);
        indent(json);
        break;
    case COLON:
        putc(':', json->stream);
        if (json->whitespace != MINIFIED) {
            fputc(' ', json->stream);
        }
        break;
    }
}

/// End a JSON value.
void end_value(Json* json)
{
    json->next_punctuation = COMMA;
}

/// Increment the indent level by one.
void push_indentation(Json* json)
{
    json->indent_level += 1;
}

/// Decrement the indent level by one.
void pop_indentation(Json* json)
{
    json->indent_level -= 1;
}

/// Append a newline and whitespace for the next line,
/// except when `whitespace` is set to `MINIFIED`.
void indent(Json* json)
{
    char indent_char = ' ';
    int n;
    switch (json->whitespace) {
    case MINIFIED:
        // In minified mode, we don't want newlines or whitespace.
        return;
    case INDENT_1:
        n = 1 * json->indent_level;
        break;
    case INDENT_2:
        n = 2 * json->indent_level;
        break;
    case INDENT_3:
        n = 3 * json->indent_level;
        break;
    case INDENT_4:
        n = 4 * json->indent_level;
        break;
    case INDENT_8:
        n = 8 * json->indent_level;
        break;
    case INDENT_TAB:
        indent_char = '\t';
        n = json->indent_level;
        break;
    }

    putc('\n', json->stream);
    for (int i = 0; i < n; i++) {
        putc(indent_char, json->stream);
    }
}