package gptoss

import (
	"cmp"
	"math"

	"github.com/ollama/ollama/fs"
	"github.com/ollama/ollama/kvcache"
	"github.com/ollama/ollama/ml"
	"github.com/ollama/ollama/ml/nn"
	"github.com/ollama/ollama/ml/nn/fast"
	"github.com/ollama/ollama/ml/nn/rope"
	"github.com/ollama/ollama/model"
	"github.com/ollama/ollama/model/input"
)

type Transformer struct {
	model.Base
	model.BytePairEncoding

	TokenEmbedding    *nn.Embedding      `gguf:"token_embd"`
	TransformerBlocks []TransformerBlock `gguf:"blk"`
	OutputNorm        *nn.RMSNorm        `gguf:"output_norm"`
	Output            *nn.Linear         `gguf:"output,alt:token_embd"`

	Options
}

// Forward implements model.Model.
func (m *Transformer) Forward(ctx ml.Context, batch input.Batch) (ml.Tensor, error) {
	hiddenStates := m.TokenEmbedding.Forward(ctx, batch.Inputs)
	positions := ctx.Input().FromIntSlice(batch.Positions, len(batch.Positions))

	one := ctx.Input().FromFloatSlice([]float32{1}, 1)
	for i, block := range m.TransformerBlocks {
		m.Cache.SetLayer(i)
		if c, ok := m.Cache.(*kvcache.WrapperCache); ok {
			// Even layers are sliding window attention.
			c.SetLayerType(i % 2)
		}

		var outputs ml.Tensor
		if len(batch.Outputs) > 0 && i == len(m.TransformerBlocks)-1 {
			outputs = ctx.Input().FromIntSlice(batch.Outputs, len(batch.Outputs))
		}

		hiddenStates = block.Forward(ctx, hiddenStates, positions, outputs, one, m.Cache, &m.Options)
	}

	hiddenStates = m.OutputNorm.Forward(ctx, hiddenStates, m.eps)
	return m.Output.Forward(ctx, hiddenStates), nil
}

func (m *Transformer) Shift(ctx ml.Context, layer int, key, shift ml.Tensor) (ml.Tensor, error) {
	return fast.RoPE(ctx, key, shift, m.headDim(), m.ropeBase, 1./m.ropeScale, m.RoPEOptions()...), nil
}

type Options struct {
	hiddenSize,
	numHeads,
	numKVHeads,
	keyLength,
	valueLength,
	numExperts,
	numExpertsUsed,
	originalContextLength int

	eps,
	ropeBase,
	ropeScale float32
}

func (o Options) RoPEOptions() []func(*rope.Options) {
	return []func(*rope.Options){
		rope.WithTypeNeoX(),
		rope.WithOriginalContextLength(o.originalContextLength),
		rope.WithExtrapolationFactor(1.),
		// NOTE: ggml sets this implicitly so there's no need to set it here
		// rope.WithAttentionFactor(0.1*float32(math.Log(float64(o.ropeScale))) + 1.0),
	}
}

func (o Options) headDim() int {
	return cmp.Or(o.keyLength, o.valueLength, o.hiddenSize/o.numHeads)
}

type TransformerBlock struct {
	Attention *AttentionBlock
	MLP       *MLPBlock
}

func (d *TransformerBlock) Forward(ctx ml.Context, hiddenStates, positions, outputs, one ml.Tensor, cache kvcache.Cache, opts *Options) ml.Tensor {
	hiddenStates = d.Attention.Forward(ctx, hiddenStates, positions, cache, opts)
	if outputs != nil {
		hiddenStates = hiddenStates.Rows(ctx, outputs)
	}

	hiddenStates = d.MLP.Forward(ctx, hiddenStates, one, opts)
	return hiddenStates
}

type AttentionBlock struct {
	Norm   *nn.RMSNorm `gguf:"attn_norm"`
	QKV    *nn.Linear  `gguf:"attn_qkv"`
	Output *nn.Linear  `gguf:"attn_out"`
	Sinks  ml.Tensor   `gguf:"attn_sinks"`
}

func (attn *AttentionBlock) Forward(ctx ml.Context, hiddenStates, positions ml.Tensor, cache kvcache.Cache, opts *Options) ml.Tensor {
	batchSize := hiddenStates.Dim(1)

	residual := hiddenStates
	hiddenStates = attn.Norm.Forward(ctx, hiddenStates, opts.eps)

	qkv := attn.QKV.Forward(ctx, hiddenStates)

	// query = qkv[..., : num_attention_heads * head_dim].reshape(batch_size, num_attention_heads, head_dim)
	query := qkv.View(ctx,
		0,
		opts.headDim(), qkv.Stride(0)*opts.headDim(),
		opts.numHeads, qkv.Stride(1),
		batchSize,
	)
	query = fast.RoPE(ctx, query, positions, opts.headDim(), opts.ropeBase, 1./opts.ropeScale, opts.RoPEOptions()...)

	// key = qkv[..., num_attention_heads * head_dim:(num_attention_heads + num_key_value_heads) * head_dim].reshape(batch_size, num_key_value_heads, head_dim)
	key := qkv.View(ctx,
		qkv.Stride(0)*opts.headDim()*opts.numHeads,
		opts.headDim(), qkv.Stride(0)*opts.headDim(),
		opts.numKVHeads, qkv.Stride(1),
		batchSize,
	)
	key = fast.RoPE(ctx, key, positions, opts.headDim(), opts.ropeBase, 1./opts.ropeScale, opts.RoPEOptions()...)

	// value = qkv[..., (num_attention_heads  + num_key_value_heads) * head_dim:].reshape(batch_size, num_key_value_heads, head_dim)
	value := qkv.View(ctx,
		qkv.Stride(0)*opts.headDim()*(opts.numHeads+opts.numKVHeads),
		opts.headDim(), qkv.Stride(0)*opts.headDim(),
		opts.numKVHeads, qkv.Stride(1),
		batchSize,
	)

	cache.Put(ctx, key, value)
	key, value, mask := cache.Get(ctx)

	query = query.Permute(ctx, 0, 2, 1, 3)
	key = key.Permute(ctx, 0, 2, 1, 3)
	value = value.Permute(ctx, 1, 2, 0, 3).Contiguous(ctx)

	scores := key.MulmatFullPrec(ctx, query)
	scores = scores.Scale(ctx, 1./math.Sqrt(float64(opts.headDim())))
	scores = scores.Add(ctx, mask)

	scores = scores.Concat(ctx, attn.Sinks.Reshape(ctx, 1, 1, opts.numHeads, 1).Repeat(ctx, 1, batchSize), 0)
	scores = scores.Softmax(ctx)
	scores = scores.Pad(ctx, -1, 0, 0, 0)

	attention := value.Mulmat(ctx, scores)
	attention = attention.Permute(ctx, 0, 2, 1, 3).Contiguous(ctx)
	attention = attention.Reshape(ctx, attention.Dim(0)*attention.Dim(1), batchSize)

	return attn.Output.Forward(ctx, attention).Add(ctx, residual)
}

type MLPBlock struct {
	Norm   *nn.RMSNorm     `gguf:"ffn_norm"`
	Router *nn.Linear      `gguf:"ffn_gate_inp"`
	GateUp *nn.LinearBatch `gguf:"ffn_gate_up_exps"`
	Down   *nn.LinearBatch `gguf:"ffn_down_exps"`
}

func (mlp *MLPBlock) Forward(ctx ml.Context, hiddenStates, one ml.Tensor, opts *Options) ml.Tensor {
	hiddenDim, sequenceLength, batchSize := hiddenStates.Dim(0), hiddenStates.Dim(1), hiddenStates.Dim(2)

	residual := hiddenStates
	hiddenStates = mlp.Norm.Forward(ctx, hiddenStates, opts.eps)

	hiddenStates = hiddenStates.Reshape(ctx, hiddenDim, sequenceLength*batchSize)
	routingWeights := mlp.Router.Forward(ctx, hiddenStates)

	selectedExperts := routingWeights.TopK(ctx, opts.numExpertsUsed)
	routingWeights = routingWeights.Reshape(ctx, 1, opts.numExperts, sequenceLength*batchSize).Rows(ctx, selectedExperts)
	routingWeights = routingWeights.Reshape(ctx, opts.numExpertsUsed, sequenceLength*batchSize).Softmax(ctx)
	routingWeights = routingWeights.Reshape(ctx, 1, opts.numExpertsUsed, sequenceLength*batchSize)

	hiddenStates = hiddenStates.Reshape(ctx, hiddenStates.Dim(0), 1, hiddenStates.Dim(1))

	hiddenStates = mlp.GateUp.Forward(ctx, hiddenStates, selectedExperts)
	hiddenStates = hiddenStates.Reshape(ctx, 2, hiddenStates.Dim(0)/2, hiddenStates.Dim(1), hiddenStates.Dim(2))

	dimStride := []int{hiddenStates.Dim(0) / 2, hiddenStates.Stride(1), hiddenStates.Dim(1), hiddenStates.Stride(2), hiddenStates.Dim(2), hiddenStates.Stride(3), hiddenStates.Dim(3)}
	hiddenStates = hiddenStates.View(ctx, 0, dimStride...).
		Contiguous(ctx).
		QuickGELU(ctx).
		Mul(ctx, hiddenStates.View(ctx, hiddenStates.Stride(0), dimStride...).Add(ctx, one))

	hiddenStates = hiddenStates.Reshape(ctx, hiddenStates.Dim(0)*hiddenStates.Dim(1), hiddenStates.Dim(2), hiddenStates.Dim(3))

	experts := mlp.Down.Forward(ctx, hiddenStates, selectedExperts)
	experts = experts.Mul(ctx, routingWeights)

	nextStates := experts.View(ctx, 0, experts.Dim(0), experts.Stride(2), experts.Dim(2))
	for i := 1; i < opts.numExpertsUsed; i++ {
		nextStates = nextStates.Add(ctx, experts.View(ctx, i*experts.Stride(1), experts.Dim(0), experts.Stride(2), experts.Dim(2)))
	}

	return nextStates.Add(ctx, residual)
}

func New(c fs.Config) (model.Model, error) {
	m := Transformer{
		TransformerBlocks: make([]TransformerBlock, c.Uint("block_count")),
		BytePairEncoding: model.NewBytePairEncoding(
			c.String("tokenizer.ggml.pretokenizer", `(?i:'s|'t|'re|'ve|'m|'ll|'d)|[^\r\n\p{L}\p{N}]?\p{L}+|\p{N}{1,3}| ?[^\s\p{L}\p{N}]+[\r\n]*|\s*[\r\n]+|\s+(?!\S)|\s+`),
			&model.Vocabulary{
				Values: c.Strings("tokenizer.ggml.tokens"),
				Types:  c.Ints("tokenizer.ggml.token_type"),
				Merges: c.Strings("tokenizer.ggml.merges"),
				AddBOS: c.Bool("tokenizer.ggml.add_bos_token", false),
				BOS:    []int32{int32(c.Uint("tokenizer.ggml.bos_token_id"))},
				AddEOS: c.Bool("tokenizer.ggml.add_eos_token", false),
				EOS: append(
					[]int32{int32(c.Uint("tokenizer.ggml.eos_token_id"))},
					c.Ints("tokenizer.ggml.eos_token_ids")...,
				),
			},
		),
		Options: Options{
			hiddenSize:            int(c.Uint("embedding_length")),
			numHeads:              int(c.Uint("attention.head_count")),
			numKVHeads:            int(c.Uint("attention.head_count_kv")),
			keyLength:             int(c.Uint("attention.key_length")),
			valueLength:           int(c.Uint("attention.value_length")),
			numExperts:            int(c.Uint("expert_count")),
			numExpertsUsed:        int(c.Uint("expert_used_count")),
			eps:                   c.Float("attention.layer_norm_rms_epsilon"),
			ropeBase:              c.Float("rope.freq_base"),
			ropeScale:             c.Float("rope.scaling.factor", 1.),
			originalContextLength: int(c.Uint("rope.scaling.original_context_length")),
		},
	}

	m.Cache = kvcache.NewWrapperCache(
		kvcache.NewSWACache(int32(c.Uint("attention.sliding_window")), m.Shift),
		kvcache.NewCausalCache(m.Shift),
	)
	m.Cache.SetConfig(ml.CacheConfig{})
	return &m, nil
}

func init() {
	model.Register("gptoss", New)
}
