package deepseek2

// uses deepseek 2 architecture but written based on deepseek 3 model

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 Options struct {
	isMLA               bool
	numExpertsUsed      int
	numExperts          int
	normTopKProb        bool
	routedScalingFactor float32

	kvLoraRank,
	qkNopeHeadDim,
	qkRopeHeadDim,
	kqNopeHeadDim,
	qkHeadDim int
	qLoraRank int
	vHeadDim  int

	hiddenSize,
	numHeads,
	numKVHeads,
	originalContextLength int

	eps,
	ropeBase,
	ropeScale float32
	kqScale float64
}

func (o Options) RoPEOptions() []func(*rope.Options) {
	attnFactor := float32(1.0 / (1.0 + 0.1*math.Log(float64(o.ropeScale))))
	return []func(*rope.Options){
		rope.WithOriginalContextLength(o.originalContextLength),
		rope.WithExtrapolationFactor(1.),
		rope.WithAttentionFactor(attnFactor),
	}
}

type Attention struct {
	Q *nn.Linear `gguf:"attn_q"`

	QA     *nn.Linear  `gguf:"attn_q_a"`
	QANorm *nn.RMSNorm `gguf:"attn_q_a_norm"`
	QB     *nn.Linear  `gguf:"attn_q_b"`

	KVA     *nn.Linear  `gguf:"attn_kv_a_mqa"`
	KVANorm *nn.RMSNorm `gguf:"attn_kv_a_norm"`
	KVB     *nn.Linear  `gguf:"attn_kv_b"`

	KB *nn.Linear `gguf:"attn_k_b"`
	VB *nn.Linear `gguf:"attn_v_b"`

	Output *nn.Linear `gguf:"attn_out,alt:attn_output"`
}

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

	var query ml.Tensor
	if opts.qLoraRank == 0 {
		query = attn.Q.Forward(ctx, hiddenStates)
	} else {
		query = attn.QA.Forward(ctx, hiddenStates)
		query = attn.QANorm.Forward(ctx, query, opts.eps)
		query = attn.QB.Forward(ctx, query)
	}

	query = query.Reshape(ctx, query.Dim(0)/opts.numHeads, opts.numHeads, seqLength)
	queryChunks := query.ChunkSections(ctx, 0, opts.qkNopeHeadDim, opts.qkRopeHeadDim)

	compressedKV := attn.KVA.Forward(ctx, hiddenStates)
	kPass := compressedKV.Slice(ctx, 0, 0, opts.kvLoraRank, 1)
	kRot := compressedKV.View(ctx,
		opts.kvLoraRank*compressedKV.Stride(0), opts.qkRopeHeadDim,
		compressedKV.Stride(1), 1,
		compressedKV.Stride(1), compressedKV.Dim(1),
	)

	qRot := fast.RoPE(ctx, queryChunks[1], positions, opts.qkRopeHeadDim, opts.ropeBase, 1./opts.ropeScale, opts.RoPEOptions()...)
	kRot = fast.RoPE(ctx, kRot, positions, opts.qkRopeHeadDim, opts.ropeBase, 1./opts.ropeScale, opts.RoPEOptions()...)
	kPass = attn.KVANorm.Forward(ctx, kPass, opts.eps)

	var attention ml.Tensor

	if !opts.isMLA { // v3
		kPass = attn.KVB.Forward(ctx, kPass)

		kv := kPass.Reshape(ctx, kPass.Dim(0)/opts.numKVHeads, opts.numKVHeads, seqLength)
		kvChunks := kv.ChunkSections(ctx, 0, opts.kqNopeHeadDim, opts.vHeadDim)

		kRot = kRot.Repeat(ctx, 1, queryChunks[0].Dim(1))
		query = qRot.Concat(ctx, queryChunks[0], 0)
		key := kRot.Concat(ctx, kvChunks[0], 0)
		attention = nn.Attention(ctx, query, key, kvChunks[1], opts.kqScale, cache)
	} else { // v3.1
		qPass := queryChunks[0].Permute(ctx, 0, 2, 1, 3)
		qPassAbsorb := attn.KB.Forward(ctx, qPass)
		qPassAbsorb = qPassAbsorb.Permute(ctx, 0, 2, 1, 3)

		query = qRot.Concat(ctx, qPassAbsorb, 0)
		kPass = kPass.Reshape(ctx, opts.kvLoraRank, 1, seqLength)
		key := kRot.Concat(ctx, kPass, 0)
		value := kPass

		attention = nn.AttentionWithVMLA(ctx, query, key, value, nil, attn.VB.Weight, opts.kqScale, cache)
	}

	attention = attention.Reshape(ctx, attention.Dim(0)*attention.Dim(1), seqLength)
	return attn.Output.Forward(ctx, attention)
}

type MLP interface {
	Forward(ml.Context, ml.Tensor, *Options) ml.Tensor
}

type sparse struct {
	Router       *nn.Linear `gguf:"ffn_gate_inp"`
	Gate         *nn.Linear `gguf:"ffn_gate_exps"`
	Up           *nn.Linear `gguf:"ffn_up_exps"`
	Down         *nn.Linear `gguf:"ffn_down_exps"`
	SharedExpert *dense     `gguf:",suf:_shexp"`
	ExpProbsBias ml.Tensor  `gguf:"exp_probs_b.bias,alt:exp_probs_b"`
}

func (moe *sparse) Moe(ctx ml.Context, hiddenStates, topKIndices, topKWeights ml.Tensor, opts *Options) ml.Tensor {
	hiddenStates = hiddenStates.Reshape(ctx, hiddenStates.Dim(0), 1, hiddenStates.Dim(1))

	upStates := moe.Up.Weight.MulmatID(ctx, hiddenStates, topKIndices)
	hiddenStates = moe.Gate.Weight.MulmatID(ctx, hiddenStates, topKIndices)
	hiddenStates = hiddenStates.SILU(ctx, upStates)

	experts := moe.Down.Weight.MulmatID(ctx, hiddenStates, topKIndices)
	experts = experts.Mul(ctx, topKWeights)

	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
}

func (moe *sparse) topKIndices(ctx ml.Context, scores ml.Tensor, opts *Options) ml.Tensor {
	if moe.ExpProbsBias != nil {
		scores = scores.Add(ctx, moe.ExpProbsBias)
	}
	topKIndices := scores.TopK(ctx, opts.numExpertsUsed)
	return topKIndices
}

func (moe *sparse) Forward(ctx ml.Context, hiddenStates ml.Tensor, opts *Options) ml.Tensor {
	residuals := hiddenStates

	routerLogits := moe.Router.Forward(ctx, hiddenStates)
	scores := routerLogits.Sigmoid(ctx)
	topKIndices := moe.topKIndices(ctx, scores, opts)
	topKWeights := scores.Reshape(ctx, 1, opts.numExperts, hiddenStates.Dim(1)).Rows(ctx, topKIndices)

	if opts.normTopKProb {
		topKWeights = topKWeights.Reshape(ctx, opts.numExpertsUsed, hiddenStates.Dim(1))
		topKWeights = topKWeights.Div(ctx, topKWeights.SumRows(ctx))
		topKWeights = topKWeights.Reshape(ctx, 1, opts.numExpertsUsed, hiddenStates.Dim(1))
	}

	topKWeights = topKWeights.Scale(ctx, float64(opts.routedScalingFactor))
	hiddenStates = moe.Moe(ctx, hiddenStates, topKIndices, topKWeights, opts)
	sharedExpertResult := moe.SharedExpert.Forward(ctx, residuals, opts)

	hiddenStates = hiddenStates.Add(ctx, sharedExpertResult)
	return hiddenStates
}

type dense struct {
	Gate *nn.Linear `gguf:"ffn_gate"`
	Up   *nn.Linear `gguf:"ffn_up"`
	Down *nn.Linear `gguf:"ffn_down"`
}

func (mlp *dense) Forward(ctx ml.Context, hiddenStates ml.Tensor, opts *Options) ml.Tensor {
	hiddenStates = mlp.Gate.Forward(ctx, hiddenStates).SILU(ctx, mlp.Up.Forward(ctx, hiddenStates))
	return mlp.Down.Forward(ctx, hiddenStates)
}

type Layer struct {
	AttentionNorm *nn.RMSNorm `gguf:"attn_norm"`
	Attention     *Attention

	MLPNorm *nn.RMSNorm `gguf:"ffn_norm"`
	MLP     MLP
}

func (t *Layer) Forward(ctx ml.Context, hiddenStates, positions, outputs ml.Tensor, cache kvcache.Cache, opts *Options) ml.Tensor {
	residual := hiddenStates
	hiddenStates = t.AttentionNorm.Forward(ctx, hiddenStates, opts.eps)
	hiddenStates = t.Attention.Forward(ctx, hiddenStates, positions, cache, opts)

	if outputs != nil {
		hiddenStates = hiddenStates.Rows(ctx, outputs)
		residual = residual.Rows(ctx, outputs)
	}

	hiddenStates = hiddenStates.Add(ctx, residual)
	residual = hiddenStates

	hiddenStates = t.MLPNorm.Forward(ctx, hiddenStates, opts.eps)
	hiddenStates = t.MLP.Forward(ctx, hiddenStates, opts)
	hiddenStates = hiddenStates.Add(ctx, residual)
	return hiddenStates
}

type Model struct {
	model.Base
	model.BytePairEncoding

	TokenEmbedding *nn.Embedding `gguf:"token_embd"`
	Layers         []Layer       `gguf:"blk"`

	OutputNorm *nn.RMSNorm `gguf:"output_norm"`
	Output     *nn.Linear  `gguf:"output,alt:token_embd"`

	*Options
}

func New(c fs.Config) (model.Model, error) {
	if c.Uint("attention.key_length_mla") == 0 {
		// non-MLA models aren't yet supported
		return nil, model.ErrUnsupportedModel
	}

	layers := make([]Layer, c.Uint("block_count"))

	firstDenseLayerIndex := int(c.Uint("leading_dense_block_count"))
	for i := range layers {
		if i < firstDenseLayerIndex {
			layers[i].MLP = &dense{}
		} else {
			layers[i].MLP = &sparse{}
		}
	}

	mScale := float32(1.0 + float64(c.Float("rope.scaling.yarn_log_multiplier"))*math.Log(float64(c.Float("rope.scaling.factor"))))
	kqScale := float64(mScale) * float64(mScale) / math.Sqrt(float64(c.Uint("attention.key_length")))

	isMLA := c.Uint("attention.key_length_mla") != 0 && c.Uint("attention.value_length_mla") != 0
	keyLength := int(cmp.Or(c.Uint("attention.key_length_mla"), c.Uint("attention.key_length")))
	valueLength := int(cmp.Or(c.Uint("attention.value_length_mla"), c.Uint("attention.value_length")))

	m := Model{
		BytePairEncoding: model.NewBytePairEncoding(
			&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", true),
				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")...,
				),
			},
			// Split regex into multiple parts (according to DeepSeek3's regex)
			"\\p{N}{1,3}",
			`[一-龥぀-ゟ゠-ヿ]+`,
			"[!\"#$%&'()*+,\\-./:;<=>?@\\[\\\\\\]^_`{|}~][A-Za-z]+|[^\r\n\\p{L}\\p{P}\\p{S}]?[\\p{L}\\p{M}]+| ?[\\p{P}\\p{S}]+[\r\n]*|\\s*[\r\n]+|\\s+(?!\\S)|\\s+",
		),
		Layers: layers,
		Options: &Options{
			isMLA:          isMLA,
			hiddenSize:     int(c.Uint("embedding_length")),
			numHeads:       int(c.Uint("attention.head_count")),
			numKVHeads:     int(c.Uint("attention.head_count_kv")),
			eps:            c.Float("attention.layer_norm_rms_epsilon"),
			ropeBase:       c.Float("rope.freq_base"),
			ropeScale:      c.Float("rope.scaling.factor", 1),
			numExperts:     int(c.Uint("expert_count")),
			numExpertsUsed: int(c.Uint("expert_used_count")),
			normTopKProb:   c.Bool("expert_weights_norm", true),

			qLoraRank:     int(c.Uint("attention.q_lora_rank")),
			kvLoraRank:    int(c.Uint("attention.kv_lora_rank")),
			qkHeadDim:     keyLength,
			vHeadDim:      valueLength,
			qkRopeHeadDim: int(c.Uint("rope.dimension_count")),
			qkNopeHeadDim: keyLength - int(c.Uint("rope.dimension_count")),
			kqNopeHeadDim: keyLength - int(c.Uint("rope.dimension_count")),

			routedScalingFactor:   c.Float("expert_weights_scale"),
			originalContextLength: int(c.Uint("rope.scaling.original_context_length")),

			kqScale: kqScale,
		},
	}

	m.Cache = kvcache.NewCausalCache(m.Shift)
	return &m, nil
}

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

func (m *Model) Forward(ctx ml.Context, batch input.Batch) (ml.Tensor, error) {
	positions := ctx.Input().FromInts(batch.Positions, len(batch.Positions))

	hiddenStates := m.TokenEmbedding.Forward(ctx, batch.Inputs)

	for i, layer := range m.Layers {
		m.Cache.SetLayer(i)

		var outputs ml.Tensor
		if i == len(m.Layers)-1 {
			outputs = batch.Outputs
		}

		hiddenStates = layer.Forward(ctx, hiddenStates, positions, outputs, m.Cache, m.Options)
	}

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

func init() {
	model.Register("deepseek2", New)
}
