const std = @import("std");
const reg = @import("registry.zig");
const util = @import("render/util.zig");
const mem = std.mem;
const Allocator = mem.Allocator;

const preamble =
    \\const std = @import("std");
    \\
    ;

const BuiltinType = struct {
    c_name: []const u8,
    zig_name: []const u8
};

const builtin_types = [_]BuiltinType{
    .{.c_name = "void", .zig_name = @typeName(void)},
    .{.c_name = "char", .zig_name = @typeName(u8)},
    .{.c_name = "float", .zig_name = @typeName(f32)},
    .{.c_name = "double", .zig_name = @typeName(f64)},
    .{.c_name = "uint8_t", .zig_name = @typeName(u8)},
    .{.c_name = "uint16_t", .zig_name = @typeName(u16)},
    .{.c_name = "uint32_t", .zig_name = @typeName(u32)},
    .{.c_name = "uint64_t", .zig_name = @typeName(u64)},
    .{.c_name = "int32_t", .zig_name = @typeName(i32)},
    .{.c_name = "int64_t", .zig_name = @typeName(i64)},
    .{.c_name = "size_t", .zig_name = @typeName(usize)},
    .{.c_name = "int", .zig_name = @typeName(c_int)},
};

fn eqlIgnoreCase(lhs: []const u8, rhs: []const u8) bool {
    if (lhs.len != rhs.len) {
        return false;
    }

    for (lhs) |c, i| {
        if (std.ascii.toLower(c) != std.ascii.toLower(rhs[i])) {
            return false;
        }
    }

    return true;
}

fn Renderer(comptime WriterType: type) type {
    return struct {
        const Self = @This();
        const WriteError = WriterType.Error;
        const RenderTypeInfoError = WriteError || error {
            OutOfMemory,
        };

        writer: WriterType,
        allocator: *Allocator,
        registry: *const reg.Registry,
        id_renderer: util.IdRenderer,

        fn init(writer: WriterType, allocator: *Allocator, registry: *const reg.Registry) Self {
            return .{
                .writer = writer,
                .allocator = allocator,
                .registry = registry,
                .id_renderer = util.IdRenderer.init(allocator, registry.tags),
            };
        }

        fn deinit(self: Self) void {
            self.id_renderer.deinit();
        }

        fn writeIdentifier(self: Self, id: []const u8) !void {
            try util.writeIdentifier(self.writer, id);
        }

        fn writeIdentifierWithCase(self: *Self, case: util.CaseStyle, id: []const u8) !void {
            try self.id_renderer.render(self.writer, case, id);
        }

        fn extractEnumFieldName(self: Self, enum_name: []const u8, field_name: []const u8) ![]const u8 {
            const tag = util.getAuthorTag(enum_name, self.registry.tags);
            const adjusted_enum_name = if (tag) |name|
                    enum_name[0 .. enum_name.len - name.len]
                else
                    enum_name;

            var enum_it = util.SegmentIterator.init(adjusted_enum_name);
            var field_it = util.SegmentIterator.init(field_name);

            while (true) {
                const rest = field_it.rest();
                const enum_segment = enum_it.next() orelse return rest;
                const field_segment = field_it.next() orelse return error.FieldNameEqualsEnumName;

                if (!eqlIgnoreCase(enum_segment, field_segment)) {
                    return rest;
                }
            }
        }

        fn render(self: *Self) !void {
            try self.writer.writeAll(preamble);

            for (self.registry.decls) |decl| {
               try self.renderDecl(decl);
            }
        }

        fn renderTypeInfo(self: *Self, type_info: reg.TypeInfo) RenderTypeInfoError!void {
            switch (type_info) {
                .name => |name| try self.renderTypeName(name),
                .command_ptr => |command_ptr| try self.renderCommandPtr(command_ptr),
                .pointer => |pointer| try self.renderPointer(pointer),
                .array => |array| try self.renderArray(array),
            }
        }

        fn renderTypeName(self: *Self, name: []const u8) !void {
            for (builtin_types) |builtin_type| {
                if (mem.eql(u8, name, builtin_type.c_name)) {
                    try self.writer.writeAll(builtin_type.zig_name);
                    return;
                }
            }

            // TODO: Handle foreign types

            if (mem.startsWith(u8, name, "vk")) {
                // Function type, always render with the exact same text for linking purposes.
                try self.writeIdentifier(name);
                return;
            } else if (mem.startsWith(u8, name, "Vk")) {
                // Type, strip namespace and write, as they are alreay in title case.
                try self.writeIdentifier(name[2..]);
                return;
            } else if (mem.startsWith(u8, name, "PFN_vk")) {
                // Function pointer type, render using same name for now
                try self.writeIdentifier(name);
                return;
            }

            try self.writeIdentifier(name);
        }

        fn renderCommandPtr(self: *Self, command_ptr: reg.Command) !void {
            try self.writer.writeAll("?fn(");
            for (command_ptr.params) |param| {
                try self.writeIdentifierWithCase(.snake, param.name);
                try self.writer.writeAll(": ");
                try self.renderTypeInfo(param.param_type);
                try self.writer.writeAll(", ");
            }
            try self.writer.writeAll(") ");
            try self.renderTypeInfo(command_ptr.return_type.*);
        }

        fn renderPointer(self: *Self, pointer: reg.Pointer) !void {
            if (pointer.is_optional) {
                try self.writer.writeByte('?');
            }

            switch (pointer.size) {
                .one => try self.writer.writeByte('*'),
                .many => try self.writer.writeAll("[*]"),
                .zero_terminated => try self.writer.writeAll("[*:0]"),
            }

            if (pointer.is_const) {
                try self.writer.writeAll("const ");
            }

            // Special case: void pointers
            if (pointer.child.* == .name and mem.eql(u8, pointer.child.name, "void")) {
                try self.writer.writeAll("c_void");
            } else {
                try self.renderTypeInfo(pointer.child.*);
            }
        }

        fn renderArray(self: *Self, array: reg.Array) !void {
            try self.writer.writeByte('[');
            switch (array.size) {
                .int => |size| try self.writer.print("{}", .{size}),
                .alias => |alias| try self.writeIdentifier(alias[3..]), //TODO: Check proper VK_ prefix
            }
            try self.writer.writeByte(']');
            try self.renderTypeInfo(array.child.*);
        }

        fn renderDecl(self: *Self, decl: reg.Declaration) !void {
            switch (decl.decl_type) {
                .container => |container| try self.renderContainer(decl.name, container),
                .enumeration => |enumeration| try self.renderEnumeration(decl.name, enumeration),
                .alias => |alias| try self.renderAlias(decl.name, alias),
                .opaque => try self.renderOpaque(decl.name),
                .typedef => |type_info| try self.renderTypedef(decl.name, type_info),
                else => {}, // unhandled for now
            }
        }

        fn renderContainer(self: *Self, name: []const u8, container: reg.Container) !void {
            try self.writer.writeAll("const ");
            try self.renderTypeName(name);
            try self.writer.writeAll(" = ");

            for (container.fields) |field| {
                if (field.bits != null) {
                    try self.writer.writeAll("packed ");
                    break;
                }
            } else {
                try self.writer.writeAll("extern ");
            }

            if (container.is_union) {
                try self.writer.writeAll("union {");
            } else {
                try self.writer.writeAll("struct {");
            }

            for (container.fields) |field| {
                try self.writeIdentifierWithCase(.snake, field.name);
                try self.writer.writeAll(": ");
                try self.renderTypeInfo(field.field_type);
                // TODO: Generate struct defaults
                // TODO: Deal with packed structs
                try self.writer.writeAll(", ");
            }

            try self.writer.writeAll("};\n");
        }

        fn renderEnumeration(self: *Self, name: []const u8, enumeration: reg.Enum) !void {
            // TODO: Handle bitmasks
            try self.writer.writeAll("const ");
            try self.renderTypeName(name);
            try self.writer.writeAll(" = extern enum {");

            for (enumeration.fields) |field| {
                if (field.value == .alias) {
                    continue;
                }

                try self.writeIdentifierWithCase(.snake, try self.extractEnumFieldName(name, field.name));

                switch (field.value) {
                    .int => |int| try self.writer.print("= {}, ", .{int}),
                    .bitpos => |pos| try self.writer.print(" = 1 << {}, ", .{pos}),
                    .bit_vector => |value| try self.writer.print(" = 0x{X}, ", .{value}),
                    .alias => unreachable,
                }
            }

            for (enumeration.fields) |field| {
                if (field.value != .alias or field.value.alias.is_compat_alias) {
                    continue;
                }

                try self.writer.writeAll("pub const ");
                try self.writeIdentifierWithCase(.snake, try self.extractEnumFieldName(name, field.name));
                try self.writer.writeAll(" = ");
                try self.writeIdentifierWithCase(.snake, try self.extractEnumFieldName(name, field.value.alias.name));
                try self.writer.writeAll(";");
            }

            try self.writer.writeAll("};\n");
        }

        fn renderAlias(self: *Self, name: []const u8, alias: reg.Alias) !void {
            try self.writer.writeAll("const ");
            try self.renderTypeName(name);
            try self.writer.writeAll(" = ");
            try self.renderTypeName(alias.name);
            try self.writer.writeAll(";\n");
        }

        fn renderOpaque(self: *Self, name: []const u8) !void {
            try self.writer.writeAll("const ");
            try self.renderTypeName(name);
            try self.writer.writeAll(" = @Type(.Opaque);\n");
        }

        fn renderTypedef(self: *Self, name: []const u8, type_info: reg.TypeInfo) !void {
            try self.writer.writeAll("const ");
            try self.renderTypeName(name);
            try self.writer.writeAll(" = ");
            try self.renderTypeInfo(type_info);
            try self.writer.writeAll(";\n");
        }
    };
}

pub fn render(writer: var, allocator: *Allocator, registry: *const reg.Registry) !void {
    var renderer = Renderer(@TypeOf(writer)).init(writer, allocator, registry);
    defer renderer.deinit();

    try renderer.render();
}