//! Some words on the build script here:
//! We cannot use a test runner here as we're building for freestanding.
//! This means we need to use addExecutable() instead of using

const std = @import("std");
const LibExeObjStep = std.build.LibExeObjStep;
const Module = std.build.Module;
const FileSource = std.build.FileSource;
const Builder = std.Build;

// alias for packages
pub const LinkerScriptStep = @import("src/modules/LinkerScriptStep.zig");
pub const cpus = @import("src/modules/cpus.zig");
pub const Board = @import("src/modules/Board.zig");
pub const Chip = @import("src/modules/Chip.zig");
pub const Cpu = @import("src/modules/Cpu.zig");
pub const MemoryRegion = @import("src/modules/MemoryRegion.zig");

pub const Backing = union(enum) {
    board: Board,
    chip: Chip,

    pub fn get_target(self: @This()) std.zig.CrossTarget {
        return switch (self) {
            .board => |brd| brd.chip.cpu.target,
            .chip => |chip| chip.cpu.target,
        };
    }
};

pub const EmbeddedExecutable = struct {
    inner: *LibExeObjStep,

    pub const AppDependencyOptions = struct {
        depend_on_microzig: bool = false,
    };

    pub fn addAppDependency(exe: *EmbeddedExecutable, name: []const u8, module: *Module, options: AppDependencyOptions) void {
        if (options.depend_on_microzig) {
            const microzig_module = exe.inner.modules.get("microzig").?;
            module.dependencies.put("microzig", microzig_module) catch @panic("OOM");
        }

        const app_module = exe.inner.modules.get("app").?;
        app_module.dependencies.put(name, module) catch @panic("OOM");
    }

    pub fn installArtifact(exe: *EmbeddedExecutable, b: *Builder) void {
        b.installArtifact(exe.inner);
    }

    pub fn addIncludePath(exe: *EmbeddedExecutable, path: []const u8) void {
        exe.inner.addIncludePath(path);
    }

    pub fn addSystemIncludePath(exe: *EmbeddedExecutable, path: []const u8) void {
        return exe.inner.addSystemIncludePath(path);
    }

    pub fn addCSourceFile(exe: *EmbeddedExecutable, file: []const u8, flags: []const []const u8) void {
        exe.inner.addCSourceFile(file, flags);
    }

    pub fn addOptions(exe: *EmbeddedExecutable, module_name: []const u8, options: *std.build.OptionsStep) void {
        exe.inner.addOptions(module_name, options);
        const app_module = exe.inner.modules.get("app").?;
        const opt_module = exe.inner.modules.get(module_name).?;
        app_module.dependencies.put(module_name, opt_module) catch @panic("OOM");
    }

    pub fn addObjectFile(exe: *EmbeddedExecutable, source_file: []const u8) void {
        exe.inner.addObjectFile(source_file);
    }
};

fn root_dir() []const u8 {
    return std.fs.path.dirname(@src().file) orelse unreachable;
}

pub const EmbeddedExecutableOptions = struct {
    name: []const u8,
    source_file: std.build.FileSource,
    backing: Backing,
    optimize: std.builtin.OptimizeMode = .Debug,
    linkerscript_source_file: ?FileSource = null,
};

pub fn addEmbeddedExecutable(
    builder: *std.build.Builder,
    opts: EmbeddedExecutableOptions,
) *EmbeddedExecutable {
    const has_board = (opts.backing == .board);
    const chip = switch (opts.backing) {
        .chip => |c| c,
        .board => |b| b.chip,
    };

    const has_hal = chip.hal != null;
    const config_file_name = blk: {
        const hash = hash_blk: {
            var hasher = std.hash.SipHash128(1, 2).init("abcdefhijklmnopq");

            hasher.update(chip.name);
            // TODO: this will likely crash for generated sources, need to
            // properly hook this up to the build cache api
            hasher.update(chip.source.getPath(builder));
            hasher.update(chip.cpu.name);
            hasher.update(chip.cpu.source.getPath(builder));

            if (opts.backing == .board) {
                hasher.update(opts.backing.board.name);
                // TODO: see above
                hasher.update(opts.backing.board.source.getPath(builder));
            }

            var mac: [16]u8 = undefined;
            hasher.final(&mac);
            break :hash_blk mac;
        };

        const file_prefix = "zig-cache/microzig/config-";
        const file_suffix = ".zig";

        var ld_file_name: [file_prefix.len + 2 * hash.len + file_suffix.len]u8 = undefined;
        const filename = std.fmt.bufPrint(&ld_file_name, "{s}{}{s}", .{
            file_prefix,
            std.fmt.fmtSliceHexLower(&hash),
            file_suffix,
        }) catch unreachable;

        break :blk builder.dupe(filename);
    };

    {
        // TODO: let the user override which ram section to use the stack on,
        // for now just using the first ram section in the memory region list
        const first_ram = blk: {
            for (chip.memory_regions) |region| {
                if (region.kind == .ram)
                    break :blk region;
            } else @panic("no ram memory region found for setting the end-of-stack address");
        };

        std.fs.cwd().makeDir(std.fs.path.dirname(config_file_name).?) catch {};
        var config_file = std.fs.cwd().createFile(config_file_name, .{}) catch unreachable;
        defer config_file.close();

        var writer = config_file.writer();

        writer.print("pub const has_hal = {};\n", .{has_hal}) catch unreachable;
        writer.print("pub const has_board = {};\n", .{has_board}) catch unreachable;
        if (has_board)
            writer.print("pub const board_name = \"{}\";\n", .{std.fmt.fmtSliceEscapeUpper(opts.backing.board.name)}) catch unreachable;

        writer.print("pub const chip_name = \"{}\";\n", .{std.fmt.fmtSliceEscapeUpper(chip.name)}) catch unreachable;
        writer.print("pub const cpu_name = \"{}\";\n", .{std.fmt.fmtSliceEscapeUpper(chip.cpu.name)}) catch unreachable;
        writer.print("pub const end_of_stack = 0x{X:0>8};\n\n", .{first_ram.offset + first_ram.length}) catch unreachable;
    }

    const microzig_module = builder.createModule(.{
        .source_file = .{ .path = comptime std.fmt.comptimePrint("{s}/src/microzig.zig", .{root_dir()}) },
    });

    microzig_module.dependencies.put("config", builder.createModule(.{
        .source_file = .{ .path = config_file_name },
    })) catch unreachable;

    microzig_module.dependencies.put("chip", builder.createModule(.{
        .source_file = chip.source,
        .dependencies = &.{
            .{ .name = "microzig", .module = microzig_module },
        },
    })) catch unreachable;

    microzig_module.dependencies.put("cpu", builder.createModule(.{
        .source_file = chip.cpu.source,
        .dependencies = &.{
            .{ .name = "microzig", .module = microzig_module },
        },
    })) catch unreachable;

    if (chip.hal) |hal_module_source| {
        microzig_module.dependencies.put("hal", builder.createModule(.{
            .source_file = hal_module_source,
            .dependencies = &.{
                .{ .name = "microzig", .module = microzig_module },
            },
        })) catch unreachable;
    }

    switch (opts.backing) {
        .board => |board| {
            microzig_module.dependencies.put("board", builder.createModule(.{
                .source_file = board.source,
                .dependencies = &.{
                    .{ .name = "microzig", .module = microzig_module },
                },
            })) catch unreachable;
        },
        else => {},
    }

    const app_module = builder.createModule(.{
        .source_file = opts.source_file,
        .dependencies = &.{
            .{ .name = "microzig", .module = microzig_module },
        },
    });

    const exe = builder.allocator.create(EmbeddedExecutable) catch unreachable;
    exe.* = EmbeddedExecutable{
        .inner = builder.addExecutable(.{
            .name = opts.name,
            .root_source_file = .{ .path = comptime std.fmt.comptimePrint("{s}/src/start.zig", .{root_dir()}) },
            .target = chip.cpu.target,
            .optimize = opts.optimize,
        }),
    };
    exe.inner.addModule("app", app_module);
    exe.inner.addModule("microzig", microzig_module);

    exe.inner.strip = false; // we always want debug symbols, stripping brings us no benefit on embedded

    // might not be true for all machines (Pi Pico), but
    // for the HAL it's true (it doesn't know the concept of threading)
    exe.inner.single_threaded = true;

    if (opts.linkerscript_source_file) |linkerscript_source_file| {
        exe.inner.setLinkerScriptPath(linkerscript_source_file);
    } else {
        const linkerscript = LinkerScriptStep.create(builder, chip) catch unreachable;
        exe.inner.setLinkerScriptPath(.{ .generated = &linkerscript.generated_file });
    }

    // TODO:
    // - Generate the linker scripts from the "chip" or "board" module instead of using hardcoded ones.
    //   - This requires building another tool that runs on the host that compiles those files and emits the linker script.
    //    - src/tools/linkerscript-gen.zig is the source file for this
    exe.inner.bundle_compiler_rt = (exe.inner.target.getCpuArch() != .avr); // don't bundle compiler_rt for AVR as it doesn't compile right now

    return exe;
}

/// This build script validates usage patterns we expect from MicroZig
pub fn build(b: *std.build.Builder) !void {
    const backings = @import("test/backings.zig");
    const optimize = b.standardOptimizeOption(.{});

    const minimal = addEmbeddedExecutable(b, .{
        .name = "minimal",
        .source_file = .{
            .path = comptime root_dir() ++ "/test/programs/minimal.zig",
        },
        .backing = backings.minimal,
        .optimize = optimize,
    });

    const has_hal = addEmbeddedExecutable(b, .{
        .name = "has_hal",
        .source_file = .{
            .path = comptime root_dir() ++ "/test/programs/has_hal.zig",
        },
        .backing = backings.has_hal,
        .optimize = optimize,
    });

    const has_board = addEmbeddedExecutable(b, .{
        .name = "has_board",
        .source_file = .{
            .path = comptime root_dir() ++ "/test/programs/has_board.zig",
        },
        .backing = backings.has_board,
        .optimize = optimize,
    });

    const core_tests = b.addTest(.{
        .root_source_file = .{
            .path = comptime root_dir() ++ "/src/core.zig",
        },
        .optimize = optimize,
    });

    const test_step = b.step("test", "build test programs");
    test_step.dependOn(&minimal.inner.step);
    test_step.dependOn(&has_hal.inner.step);
    test_step.dependOn(&has_board.inner.step);
    test_step.dependOn(&b.addRunArtifact(core_tests).step);
}