const std = @import("std");
const lv2 = @import("lv2_helpers.zig");
const c = lv2.c;
const bmp = @import("bmp_valid.zig");

const log = std.log.scoped(.scritcher_image);
const plugins = @import("plugin.zig");

/// Buffer size for main image copying.
pub const BufferSize: usize = 300000;

pub const ImageError = error{
    OpenFail,
    InvalidPlugin,
    UnknownPlugin,
    InvalidSymbol,
    InstantiateFail,
    WriteFail,
    PluginLoadFail,
};

/// Low level integration function with libsndfile.
pub fn sopen(
    allocator: std.mem.Allocator,
    path: []const u8,
    mode: i32,
    fmt: *c.SF_INFO,
) !*c.SNDFILE {
    var cstr_path = try std.cstr.addNullByte(allocator, path);
    defer allocator.free(cstr_path);

    var file = c.sf_open(cstr_path.ptr, mode, fmt);
    const st: i32 = c.sf_error(file);

    if (st != 0) {
        log.debug("Failed to open {s} ({s})", .{
            path,
            c.sf_error_number(st),
        });

        return ImageError.OpenFail;
    }

    const frames_on_end = c.sf_seek(file, 0, c.SEEK_END);
    _ = c.sf_seek(file, 0, c.SEEK_SET);
    try std.testing.expectEqual(fmt.frames, frames_on_end);

    const frames_on_end_by_end = c.sf_seek(file, frames_on_end, c.SEEK_SET);
    try std.testing.expectEqual(frames_on_end, frames_on_end_by_end);

    log.debug("frames on end: {}, frame on end (2): {}", .{ frames_on_end, frames_on_end_by_end });

    return file.?;
}

pub fn swrite(file: *c.SNDFILE, buf: [*]f32, frames: i64) !void {
    const count = c.sf_writef_float(file, buf, frames);

    if (count != frames) {
        log.debug("Wanted to write {}, got {}", .{ frames, count });
        return ImageError.WriteFail;
    }
}

pub fn sseek(file: *c.SNDFILE, offset: usize) void {
    const offset_i64 = @intCast(i64, offset);
    const frames = c.sf_seek(file, offset_i64, c.SEEK_SET);
    const frames_current = c.sf_seek(file, 0, c.SEEK_CUR);
    std.debug.assert(frames == frames_current);

    if (frames != offset_i64) {
        log.debug("failed to seek to {} (seeked {} frames, offset_i64={})", .{ offset, frames, offset_i64 });
    }
}

/// Caller owns the returned memory.
pub fn temporaryName(allocator: std.mem.Allocator) ![]u8 {
    const template_start = "/temp/temp_";
    const template = "/tmp/temp_XXXXXXXXXXXXXXXXXXXXX";
    var nam = try allocator.alloc(u8, template.len);
    std.mem.copy(u8, nam, template);

    const seed = @truncate(u64, @bitCast(u128, std.time.nanoTimestamp()));
    var r = std.rand.DefaultPrng.init(seed);

    var fill = nam[template_start.len..nam.len];

    var i: usize = 0;
    while (i < 100) : (i += 1) {
        // generate a random uppercase letter, that is, 65 + random number.
        for (fill) |_, f_idx| {
            var idx = @intCast(u8, r.random().uintLessThan(u5, 24));
            var letter = @as(u8, 65) + idx;
            fill[f_idx] = letter;
        }

        // if we fail to access it, we assume it doesn't exist and return it.
        var tmp_file: std.fs.File = std.fs.cwd().openFile(
            nam,
            .{ .mode = .read_only },
        ) catch |err| {
            if (err == error.FileNotFound) return nam else continue;
        };

        // if we actually found someone, close the handle so that we don't
        // get EMFILE later on.
        tmp_file.close();
    }

    return error.TempGenFail;
}

pub fn mkSfInfo() c.SF_INFO {
    return c.SF_INFO{
        .frames = @as(c_int, 0),
        .samplerate = @as(c_int, 44100),
        .channels = @as(c_int, 1),
        .format = c.SF_FORMAT_ULAW | c.SF_FORMAT_RAW | c.SF_ENDIAN_BIG,
        .sections = @as(c_int, 0),
        .seekable = @as(c_int, 0),
    };
}

pub const Image = struct {
    allocator: std.mem.Allocator,

    /// Pointer to the underlying libsndfile's SNDFILE struct.
    sndfile: *c.SNDFILE,

    /// Current sound file's framecount.
    frames: usize,

    /// The original image file path.
    path: []const u8,

    /// Represents the current path being worked on.
    curpath: []const u8,

    /// Open a BMP image for later.
    pub fn open(allocator: std.mem.Allocator, path: []const u8) !*Image {
        var in_fmt = mkSfInfo();
        var sndfile = try sopen(allocator, path, c.SFM_READ, &in_fmt);

        var image = try allocator.create(Image);

        std.debug.assert(in_fmt.frames > @as(i64, 0));
        std.debug.assert(in_fmt.seekable == @as(i32, 1));

        image.* = Image{
            .allocator = allocator,
            .sndfile = sndfile,
            .path = path,
            .curpath = path,
            .frames = @intCast(usize, in_fmt.frames),
        };

        return image;
    }

    pub fn clone(self: *Image) !*Image {
        var in_fmt = mkSfInfo();
        // clone sndfile
        var sndfile = try sopen(self.allocator, self.curpath, c.SFM_READ, &in_fmt);
        std.debug.assert(self.frames == @intCast(usize, in_fmt.frames));

        var image = try self.allocator.create(Image);

        std.debug.assert(in_fmt.frames > @as(i64, 0));
        std.debug.assert(in_fmt.seekable == @as(i32, 1));

        image.* = Image{
            .allocator = self.allocator,
            .sndfile = sndfile,
            .path = self.path,
            .curpath = self.curpath,
            .frames = @intCast(usize, in_fmt.frames),
        };

        return image;
    }

    pub fn close(self: *Image) void {
        var st: i32 = c.sf_close(self.sndfile);
        if (st != 0) {
            log.debug("Failed to close {s} ({s})", .{
                self.path,
                c.sf_error_number(st),
            });
        }

        self.allocator.free(self.path);
        self.allocator.free(self.curpath);

        var allocator = self.allocator;
        self.* = undefined;
        allocator.destroy(self);
    }

    pub fn read(self: *Image, file_chans: c_int, buf: []f32) bool {
        const n_read: c.sf_count_t = c.sf_readf_float(self.sndfile, buf.ptr, 1);
        const buf_chans = @intCast(c_int, buf.len);

        var i = file_chans - 1;
        while (i < buf_chans) : (i += 1) {
            //buf[@intCast(usize, i)] = buf[i % file_chans];
            buf[@intCast(usize, i)] = buf[@intCast(usize, @mod(i, file_chans))];
        }

        return n_read == 1;
    }

    /// Copy bytes from the current file to out_file.
    fn copyBytes(
        self: *Image,
        out_file: *c.SNDFILE,
        start: usize,
        end: usize,
    ) !void {
        var buf = try self.allocator.alloc(f32, BufferSize);
        defer self.allocator.free(buf);

        var i: usize = start;

        // we do sf_seek() calls to make sure we are actually on the start
        // and actually end at the end position for the file.
        sseek(self.sndfile, start);
        sseek(out_file, start);

        while (i <= end) : (i += buf.len) {
            log.debug("\t\ti={d}, buf.len={d}, end={d}", .{ i, buf.len, end });
            sseek(self.sndfile, i);
            sseek(out_file, i);

            const bytes_until_end = end - i;

            var read_bytes: i64 = undefined;
            var view: []f32 = buf[0..buf.len];

            if (bytes_until_end < buf.len) {
                read_bytes = c.sf_readf_float(self.sndfile, buf.ptr, @intCast(i64, bytes_until_end));
                view = buf[0..bytes_until_end];
            } else {
                read_bytes = c.sf_readf_float(self.sndfile, buf.ptr, @intCast(i64, buf.len));
            }

            try swrite(out_file, view.ptr, @intCast(i64, view.len));
        }

        sseek(self.sndfile, end);
        sseek(out_file, end);
    }

    fn getSeekPos(self: *Image, position: plugins.Position) plugins.SeekPos {
        const file_end = self.frames;
        var seek_pos = position.seekPos(file_end);
        log.debug("\tstart {d} end {d}", .{ seek_pos.start, seek_pos.end });
        return seek_pos;
    }

    pub fn reopen(self: *Image, path: []const u8) !void {
        var in_fmt = mkSfInfo();

        self.sndfile = try sopen(self.allocator, path, c.SFM_READ, &in_fmt);
        // std.testing.expectEqual(self.frames, @intCast(usize, in_fmt.frames));

        self.curpath = path;
        self.frames = @intCast(usize, in_fmt.frames);

        log.debug("\timage: reopened on '{s}' (frames={d}, fmt.frames={d})", .{
            self.curpath,
            self.frames,
            in_fmt.frames,
        });
    }

    pub fn checkValid(self: *Image) !void {
        var file = try std.fs.cwd().openFile(self.path, .{ .mode = .read_only });
        defer file.close();

        // main bmp header:
        //  2 bytes for magic header
        //  4 bytes for size in bytes
        //  2 bytes ?
        //  2 bytes ?
        //  4 bytes for pixel array offset
        var magic = [2]u8{ 0, 0 };
        _ = try file.read(&magic);

        if (std.mem.endsWith(u8, self.path, ".bmp"))
            try bmp.magicValid(&magic);
    }

    /// Run a plugin over the image.
    /// This setups a new lilv world/plugin among other things.
    /// The internal SNDFILE pointer is modified to point to the output of the
    /// plugin run.
    pub fn runPlugin(
        self: *Image,
        plugin_uri: []const u8,
        position: plugins.Position,
        params: plugins.ParamList,
    ) !void {
        var timer = try std.time.Timer.start();

        var ctx = try plugins.makeContext(self.allocator, plugin_uri);
        defer ctx.deinit();

        var ports = try lv2.setupPorts(&ctx);
        defer ctx.allocator.free(ports);

        if (ctx.n_audio_in > 2) {
            log.debug("plugin <{s}> has more than two inputs.", .{plugin_uri});
            return ImageError.InvalidPlugin;
        }

        if (ctx.n_audio_out > 2) {
            log.debug("plugin <{s}> has more than two outputs.", .{plugin_uri});
            return ImageError.InvalidPlugin;
        }

        // now, for each param for the plugin, we find its port, and set
        // the value for the port there.
        for (params.items) |param| {
            var sym_cstr = try std.cstr.addNullByte(self.allocator, param.sym);
            defer self.allocator.free(sym_cstr);

            var sym = c.lilv_new_string(ctx.world, sym_cstr.ptr);
            const port = c.lilv_plugin_get_port_by_symbol(ctx.plugin, sym) orelse {
                log.debug("assert fail: symbol {s} not found on port", .{param.sym});
                return ImageError.InvalidSymbol;
            };

            c.lilv_node_free(sym);

            var idx = c.lilv_port_get_index(ctx.plugin, port);
            log.debug("\tset sym={s}, idx={d} to val={}", .{
                param.sym,
                idx,
                param.value,
            });
            (&ports[idx]).value = param.value;
        }

        // now we need to generate a temporary file and put the output of
        // running the plugin on that file
        var tmpnam = try temporaryName(self.allocator);
        log.debug("\trunning plugin from '{s}' to '{s}'", .{ self.curpath, tmpnam });

        var out_fmt = mkSfInfo();
        var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);

        var rctx = try plugins.RunContext.init(self.allocator, ctx.plugin);
        defer rctx.deinit();

        rctx.connectPorts(ports);
        lv2.lilv_instance_activate(rctx.instance);

        // now that we have everything setup, we need to make the part where we
        // just copy the original image and the part where we run the plugin
        // over the image.

        const seek_pos = self.getSeekPos(position);

        // there are four main stages:
        // - the bmp header copy
        // - pre-plugin
        // - plugin
        // - post-plugin

        // pre-plugin copy, merged with bmp header copy
        try self.copyBytes(
            out_file,
            @as(usize, 0),
            seek_pos.start,
        );

        sseek(self.sndfile, seek_pos.start);

        var i: usize = seek_pos.start;
        log.debug("\tseek pos start: {d} end: {d}", .{ seek_pos.start, seek_pos.end });

        var inbuf = &rctx.buffers.in;
        var outbuf = &rctx.buffers.out;

        while (i <= seek_pos.end) : (i += 1) {
            inbuf[0] = 0;
            inbuf[1] = 0;

            const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
            if (read_bytes == 0) {
                log.debug("WARN! reached EOF at idx={d}", .{i});
                break;
            }

            // trick plugins into having correct stereo signal from
            // my mono input
            inbuf[1] = inbuf[0];

            lv2.lilv_instance_run(rctx.instance, 1);
            try swrite(out_file, outbuf, 1);
        }

        sseek(self.sndfile, seek_pos.end);

        // post-plugin copy
        try self.copyBytes(
            out_file,
            seek_pos.end + 1,
            self.frames,
        );

        c.sf_write_sync(out_file);
        _ = c.sf_close(out_file);
        _ = c.sf_close(self.sndfile);

        try self.reopen(tmpnam);
        try self.checkValid();

        var time_taken = timer.read();
        log.debug("\ttook {d:.2}ms running plugin", .{time_taken / std.time.us_per_ms});
    }

    pub fn saveTo(self: *Image, out_path: []const u8) !void {
        log.debug("\timg: copy from '{s}' to '{s}'", .{ self.curpath, out_path });
        try std.fs.copyFileAbsolute(self.curpath, out_path, .{});
    }

    pub fn runCustomPlugin(
        self: *Image,
        comptime Plugin: type,
        position: plugins.Position,
        extra: anytype,
    ) !void {
        var plugin_opt: ?Plugin = Plugin.init(self.allocator, extra);
        if (plugin_opt == null) {
            return ImageError.PluginLoadFail;
        }

        var plugin = plugin_opt.?;
        defer plugin.deinit();

        const decls = comptime std.meta.declarations(Plugin);
        inline for (decls) |decl| {
            if (comptime std.mem.eql(u8, decl.name, "setup")) {
                try plugin.setup();
            }
        }

        // the code here is a copypaste of runPlugin() without the specific
        // lilv things.
        var tmpnam = try temporaryName(self.allocator);
        log.debug("\trunning CUSTOM plugin from '{s}' to '{s}'", .{ self.curpath, tmpnam });

        var out_fmt = mkSfInfo();
        var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);

        var bufs = plugins.RunBuffers{};
        const seek_pos = self.getSeekPos(position);

        // make sure we start from 0
        sseek(self.sndfile, 0);

        // there are four main stages:
        // - the bmp header copy
        // - pre-plugin
        // - CUSTOM plugin
        // - post-plugin

        // pre-plugin copy, merged with bmp header copy
        try self.copyBytes(
            out_file,
            @as(usize, 0),
            seek_pos.start,
        );

        sseek(self.sndfile, seek_pos.start);

        var i: usize = seek_pos.start;
        log.debug("\tseek pos start: {d} end: {d}", .{ seek_pos.start, seek_pos.end });

        var inbuf = &bufs.in;
        var outbuf = &bufs.out;

        while (i <= seek_pos.end) : (i += 1) {
            const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
            if (read_bytes == 0) {
                log.debug("WARN! reached EOF at idx={d}", .{i});
                break;
            }

            plugin.run(&bufs);
            try swrite(out_file, outbuf, 1);
        }

        sseek(self.sndfile, seek_pos.end);

        // post-plugin copy
        try self.copyBytes(
            out_file,
            seek_pos.end + 1,
            self.frames,
        );

        c.sf_write_sync(out_file);
        _ = c.sf_close(out_file);
        _ = c.sf_close(self.sndfile);

        // reopen the file as SFM_READ so we can run plugin chains etc
        try self.reopen(tmpnam);
        try self.checkValid();
    }
};