Backlog/engine/core/src/configVars.zig

pub const ConfigRegistry = struct {
    pub var NeonObjectTable: core.EngineObjectVTable = core.EngineObjectVTable.from(@This(), "core.ConfigRegistry");

    allocator: std.mem.Allocator = undefined,
    configMap: ?ConfigMap = null,

    pub fn create(self: *@This(), allocator: std.mem.Allocator, first: bool) !void {
        if (!first)
            return;

        self.* = .{
            .allocator = allocator,
        };
    }

    // by convention this should be in the root
    // content path
    //
    // with the name <programName>.toml
    pub fn loadConfigFile(self: *@This(), configName: []const u8) !void {
        const configFile = core.fs().loadFile(configName) catch {
            core.engine_log("unable to load configuration file {s}", .{configName});
            return;
        };
        defer core.fs().unmap(configFile);

        const parser = try Parser.create(self.allocator);
        parser.fileName = configName;
        defer parser.destroy();

        self.configMap = try parser.parseBytes(self.allocator, configFile.bytesNoEnd());

        core.engine_log("config file loaded {d} keys set", .{self.configMap.?.mapValues.count()});

        // parse and tokenize the config file
        // self.tokenizeConfigFile();

    }

    pub fn destroy(self: *@This()) void {
        if (self.configMap) |*map| {
            map.deinit();
        }
    }
};

pub fn configVar(comptime T: type, configName: []const u8, default: T) T {
    return getConfigVar(T, configName) orelse default;
}

pub const getConfigRegistry = core.EngineObject(ConfigRegistry).get;

pub fn getConfigVar(comptime T: type, configName: []const u8) ?T {
    const ctx = getConfigRegistry();

    if (ctx.configMap) |map| {
        if (map.mapValues.get(configName)) |v| {
            switch (v.value) {
                .number => |number| {
                    switch (@typeInfo(T)) {
                        .int => {
                            return @intFromFloat(number);
                        },
                        .float => {
                            return @floatCast(number);
                        },
                        else => {
                            core.engine_err("tried to get config {s} but it isn't a number", .{configName});
                            return null;
                        },
                    }
                },
                .string => |string| {
                    switch (@typeInfo(T)) {
                        .pointer => |pointerInfo| {
                            if (pointerInfo.child == u8) {
                                return string;
                            }
                        },
                        else => {
                            core.engine_err("tried to get config {s} but it isn't a string", .{configName});
                            return null;
                        },
                    }
                },
            }
        }
    }

    return null;
}

const lastSetBy_referenceInit: []const u8 = "reference";
const lastSetBy_configFile: []const u8 = "config file";

pub const ConfigValueEntry = struct {
    lastSetBy: []const u8 = lastSetBy_referenceInit,
    value: union(enum(u8)) {
        number: f64,
        string: []const u8,
    },
};

pub const ConfigMap = struct {
    backingAllocator: std.mem.Allocator,
    mapValues: std.StringHashMapUnmanaged(ConfigValueEntry) = .{},
    arena: std.heap.ArenaAllocator,
    //stringList: std.ArrayListUnmanaged([]const u8) = .{},

    pub fn init(allocator: std.mem.Allocator) !@This() {
        return .{
            .backingAllocator = allocator,
            .arena = std.heap.ArenaAllocator.init(allocator),
        };
    }

    pub fn pushMapValue(self: *@This(), key: []const u8, value: []const u8) !void {
        // take ownership of both strings
        const allocator = self.arena.allocator();

        const k = try allocator.dupe(u8, key);

        var mapValue: ConfigValueEntry = .{ .value = undefined };
        mapValue.lastSetBy = lastSetBy_configFile;

        if (value[0] == '"') {
            if (value[value.len - 1] != '"') {
                return error.MissingClosingQuote;
            }

            mapValue.value = .{
                .string = try allocator.dupe(u8, value[1 .. value.len - 1]),
            };
        } else if (std.fmt.parseFloat(f64, value) catch null) |flt| {
            mapValue.value = .{ .number = flt };
        } else {
            return error.UnableToParse;
        }

        try self.mapValues.put(allocator, k, mapValue);
    }

    pub fn deinit(self: *@This()) void {
        self.arena.deinit();
    }
};

// A Very nonstandard and very dumb ini parser
pub const Parser = struct {
    backingAllocator: std.mem.Allocator,
    arena: std.heap.ArenaAllocator,
    allocator: std.mem.Allocator = undefined,

    fileName: []const u8 = "unknown file",
    lineNumber: usize = 0,
    lineEnd: usize = 0,
    lineStart: usize = 0,
    bytes: []const u8 = undefined,
    outputMap: ?ConfigMap = null,

    configSection: ?[]const u8 = null,

    pub fn create(allocator: std.mem.Allocator) !*@This() {
        const self = try allocator.create(@This());

        self.* = .{
            .backingAllocator = allocator,
            .arena = std.heap.ArenaAllocator.init(allocator),
        };
        self.allocator = self.arena.allocator();

        return self;
    }

    pub fn nextLine(self: *@This()) ?[]const u8 {
        while (std.ascii.isWhitespace(self.bytes[self.lineEnd])) : (self.lineEnd += 1) {
            if (self.lineEnd + 1 >= self.bytes.len) {
                return null;
            }
        }

        self.lineStart = self.lineEnd;

        while (self.bytes[self.lineEnd] != '\r' and self.bytes[self.lineEnd] != '\n') : (self.lineEnd += 1) {
            if (self.lineEnd + 1 >= self.bytes.len) {
                break;
            }
        }

        self.lineNumber += 1;

        if (self.bytes[self.lineStart] == 0) {
            return null;
        }

        return self.bytes[self.lineStart..self.lineEnd];
    }

    fn stripWhiteSpace(l: []const u8) []const u8 {
        if (l.len == 0) {
            return l;
        }

        var s: usize = 0;
        var e: usize = l.len;

        while (std.ascii.isWhitespace(l[s]) and s < l.len) : (s += 1) {}

        while (std.ascii.isWhitespace(l[e - 1]) and e - 1 > 0) : (e -= 1) {}

        return l[s..e];
    }

    fn printError(self: *@This(), comptime fmt: []const u8, args: anytype) !void {
        if (core.getLogger()) |logger| {
            try logger.print(core.colors.Color.Red, fmt, args);
            try logger.print(core.colors.Color.Red, "[Config ]: Config File Parse Error> {s}:{d} \n", .{ self.fileName, self.lineNumber });
        }
    }

    pub fn parseLabel(self: *@This(), l: []const u8) !?[]const u8 {
        if (l[l.len - 1] != ']') {
            core.engine_err("\n expected closing brace ] in label..\n fatal error\n{d}: {s} \n{s}:{d}", .{ self.lineNumber, l, self.fileName, self.lineNumber });
            try self.printError("expected closing brace ] in label statement. fatal.", .{});
            return error.UnableToParse;
        }

        var line = l[1 .. l.len - 1];
        line = stripWhiteSpace(line);
        // core.engine_log("label        : '{s}'", .{line});

        return line;
    }

    pub fn parseStatement(self: *@This(), line: []const u8) !?struct { left: []const u8, right: []const u8 } {
        var s: usize = 0;

        while (s < line.len and line[s] != '=') : (s += 1) {}

        if (s == line.len) {
            try self.printError("missing right hand side of assignment after '=' {s} skipping..", .{line});
            return null;
        }

        const left = stripWhiteSpace(line[0..s]);
        const right = stripWhiteSpace(line[s + 1 .. line.len]);

        // core.engine_log("statement    : left '{s}' '{s}'", .{ left, right });

        return .{ .left = left, .right = right };
    }

    // line should already be whitespace stripped
    pub fn parseLine(self: *@This(), l: []const u8) !void {
        var i: usize = 0;
        var line = l;

        // strip comments
        while (i < line.len) : (i += 1) {
            if (line[i] == '#') {
                line = line[0..i];
                break;
            }
        }

        i = 0;

        while (i < line.len) : (i += 1) {
            if (line[i] == '[') {
                const section = try self.parseLabel(line[i..line.len]);
                if (section) |sect| {
                    self.configSection = sect;
                }
                break;
            }
            if (line[i] == '=') {
                if (try self.parseStatement(line)) |statement| {
                    var fullVarName = statement.left;
                    defer self.allocator.free(fullVarName);
                    if (self.configSection) |section| {
                        // use temporary allocator
                        fullVarName = try std.fmt.allocPrint(self.allocator, "{s}.{s}", .{ section, fullVarName });
                    }

                    // takes ownership of both strings;
                    try self.outputMap.?.pushMapValue(fullVarName, statement.right);
                }
                break;
            }
        }
    }

    pub fn parseBytes(self: *@This(), allocator: std.mem.Allocator, bytes: []const u8) !ConfigMap {
        self.outputMap = try ConfigMap.init(allocator);

        self.bytes = bytes;
        if (self.bytes.len == 0) {
            return self.outputMap.?;
        }

        self.lineStart = 0;
        self.lineEnd = 0;

        while (self.nextLine()) |line| {
            // core.engine_log("ConfigParser > {s}", .{line});
            self.parseLine(line) catch break;
        }

        return self.outputMap.?;
    }

    pub fn destroy(self: *@This()) void {
        self.arena.deinit();
        self.backingAllocator.destroy(self);
    }
};

pub fn setupConfigs(configFilePath: []const u8) !void {
    _ = try core.createObject(ConfigRegistry, .{});
    core.engine_log("loading configs {s}", .{configFilePath});
    try getConfigRegistry().loadConfigFile(configFilePath);
}

pub fn ConfigEntry(comptime T: type) type {
    return struct {
        value: ?T = null,
        default: T,
        configName: []const u8,

        pub fn make(name: []const u8, default: T) void {
            return .{ .default = default, .name = name };
        }
    };
}

const core = @import("core.zig");
const std = @import("std");