// Package translate converts between Plexum's canonical.TurnRequest /
// canonical.TurnEvent shapes and the Anthropic Messages API shapes the
// internal/anthropic client emits.
//
// Round-trip-able for text + thinking blocks; tool_use / tool_result
// passes through structurally. Block-level signatures (the opaque
// thinking signature Anthropic issues) are preserved when present.
package translate

import (
	"encoding/json"
	"fmt"

	"git.hangman-lab.top/hzhang/Plexum-sdk-go/canonical"

	"git.hangman-lab.top/hzhang/Plexum-anthropic-compat-client/anthropic"
)

// CanonicalToAnthropic converts a Plexum TurnRequest into an Anthropic
// MessagesRequest. modelID overrides the canonical req.Model so callers
// can map (e.g. "minimax/MiniMax-M2.7" → "MiniMax-M2.7") for the wire.
func CanonicalToAnthropic(req canonical.TurnRequest, modelID string, defaultMaxTokens int) (anthropic.MessagesRequest, error) {
	out := anthropic.MessagesRequest{
		Model:     modelID,
		MaxTokens: req.MaxTokens,
	}
	if out.MaxTokens <= 0 {
		out.MaxTokens = defaultMaxTokens
	}
	if req.Temperature != 0 {
		t := req.Temperature
		out.Temperature = &t
	}
	if len(req.StopSequences) > 0 {
		out.StopSequences = append([]string{}, req.StopSequences...)
	}
	// System: Plexum stores System as []Block; Anthropic accepts string
	// or []ContentBlock. We always use the []block form when we have any
	// non-trivial blocks so cache_control etc. pass through losslessly.
	if len(req.System) > 0 {
		sysBlocks := make([]anthropic.ContentBlock, 0, len(req.System))
		for _, b := range req.System {
			sysBlocks = append(sysBlocks, blockToAnthropic(b))
		}
		out.System = sysBlocks
	}
	// Messages.
	for _, m := range req.Messages {
		am := anthropic.Message{Role: roleToAnthropic(m.Role)}
		for _, b := range m.Content {
			am.Content = append(am.Content, blockToAnthropic(b))
		}
		out.Messages = append(out.Messages, am)
	}
	// Tools.
	for _, t := range req.Tools {
		out.Tools = append(out.Tools, anthropic.ToolDef{
			Name: t.Name, Description: t.Description, InputSchema: t.InputSchema,
		})
	}
	if req.ToolChoice != nil {
		out.ToolChoice = &anthropic.ToolChoice{Type: req.ToolChoice.Type, Name: req.ToolChoice.Name}
	}
	if req.Thinking != nil {
		mode := "disabled"
		if req.Thinking.Enabled {
			mode = "enabled"
		}
		out.Thinking = &anthropic.ThinkingConfig{
			Type:         mode,
			BudgetTokens: req.Thinking.Budget,
		}
	}
	return out, nil
}

func roleToAnthropic(r canonical.Role) string {
	switch r {
	case canonical.RoleUser:
		return "user"
	case canonical.RoleAssistant:
		return "assistant"
	default:
		return string(r)
	}
}

// blockToAnthropic converts ONE canonical.Block into the loose
// map-shaped ContentBlock Anthropic expects. Per-type handling:
//
//   - TextBlock         → {"type":"text", "text":..., "cache_control"?}
//   - ToolUseBlock      → {"type":"tool_use", "id":..., "name":..., "input":...}
//   - ToolResultBlock   → {"type":"tool_result", "tool_use_id":..., "content":[...], "is_error"?}
//   - ThinkingBlock     → {"type":"thinking", "thinking":..., "signature":...}
//
// Unknown block types serialize to their JSON form via canonical's
// own marshaller (fallback path).
func blockToAnthropic(b canonical.Block) anthropic.ContentBlock {
	switch v := b.(type) {
	case *canonical.TextBlock:
		out := anthropic.ContentBlock{"type": "text", "text": v.Text}
		if v.CacheControl != nil {
			out["cache_control"] = v.CacheControl
		}
		return out
	case *canonical.ToolUseBlock:
		out := anthropic.ContentBlock{
			"type": "tool_use", "id": v.ID, "name": v.Name,
		}
		if len(v.Input) > 0 {
			out["input"] = json.RawMessage(v.Input)
		} else {
			out["input"] = map[string]any{}
		}
		return out
	case *canonical.ToolResultBlock:
		inner := make([]anthropic.ContentBlock, 0, len(v.Content))
		for _, ib := range v.Content {
			inner = append(inner, blockToAnthropic(ib))
		}
		out := anthropic.ContentBlock{
			"type": "tool_result", "tool_use_id": v.ToolUseID, "content": inner,
		}
		if v.IsError {
			out["is_error"] = true
		}
		return out
	case *canonical.ThinkingBlock:
		return anthropic.ContentBlock{
			"type": "thinking", "thinking": v.Thinking, "signature": v.Signature,
		}
	default:
		// Best-effort generic: marshal then unmarshal into a map.
		raw, err := json.Marshal(b)
		if err != nil {
			return anthropic.ContentBlock{"type": "text", "text": fmt.Sprintf("[unsupported block: %T]", b)}
		}
		var m map[string]any
		if err := json.Unmarshal(raw, &m); err != nil {
			return anthropic.ContentBlock{"type": "text", "text": string(raw)}
		}
		return m
	}
}

// Translator turns a stream of anthropic.Event into a stream of
// canonical.TurnEvent. Tracks per-content-block state (current type +
// id + name) because Anthropic's deltas carry only the block index.
type Translator struct {
	// Per-block tracking — index → metadata.
	blocks   map[int]*blockState
	finalReason canonical.StopReason
	finalUsage  canonical.Usage
}

type blockState struct {
	Kind string // "text" | "thinking" | "tool_use"
	ID   string // tool_use only
	Name string // tool_use only
}

// NewTranslator constructs a fresh per-turn Translator.
func NewTranslator() *Translator {
	return &Translator{blocks: map[int]*blockState{}}
}

// Translate consumes one anthropic.Event and returns 0..N
// canonical.TurnEvents. The translator owns no internal channel —
// caller drives the loop.
func (t *Translator) Translate(ev anthropic.Event) []canonical.TurnEvent {
	switch ev.Type {
	case "message_start":
		out := []canonical.TurnEvent{{Type: canonical.EventMessageStart}}
		if ev.Message != nil && ev.Message.Usage != nil {
			t.finalUsage = toCanonicalUsage(ev.Message.Usage)
		}
		return out

	case "ping":
		return nil // keepalive

	case "content_block_start":
		if ev.ContentBlock == nil {
			return nil
		}
		st := &blockState{Kind: ev.ContentBlock.Type, ID: ev.ContentBlock.ID, Name: ev.ContentBlock.Name}
		t.blocks[ev.Index] = st
		switch st.Kind {
		case "tool_use":
			return []canonical.TurnEvent{{
				Type: canonical.EventToolCallStart, ToolCallID: st.ID, ToolName: st.Name,
			}}
		case "text":
			// Some servers emit content_block_start with non-empty
			// text seed; surface that.
			if ev.ContentBlock.Text != "" {
				return []canonical.TurnEvent{{
					Type: canonical.EventTextDelta, Text: ev.ContentBlock.Text,
				}}
			}
		case "thinking":
			if ev.ContentBlock.Thinking != "" {
				return []canonical.TurnEvent{{
					Type: canonical.EventThinkingDelta, Thinking: ev.ContentBlock.Thinking,
				}}
			}
		}
		return nil

	case "content_block_delta":
		if ev.Delta == nil {
			return nil
		}
		st := t.blocks[ev.Index]
		switch ev.Delta.Type {
		case "text_delta":
			return []canonical.TurnEvent{{Type: canonical.EventTextDelta, Text: ev.Delta.Text}}
		case "thinking_delta":
			return []canonical.TurnEvent{{Type: canonical.EventThinkingDelta, Thinking: ev.Delta.Thinking}}
		case "input_json_delta":
			if st == nil {
				return nil
			}
			return []canonical.TurnEvent{{
				Type: canonical.EventToolCallDelta,
				ToolCallID: st.ID, ToolName: st.Name,
				PartialJSON: ev.Delta.PartialJSON,
			}}
		case "signature_delta":
			// Signature lands on EventThinkingEnd at block_stop time;
			// stash on the block state.
			if st != nil {
				st.Name = ev.Delta.Signature // reuse Name as scratch
			}
			return nil
		}
		return nil

	case "content_block_stop":
		st := t.blocks[ev.Index]
		if st == nil {
			return nil
		}
		delete(t.blocks, ev.Index)
		switch st.Kind {
		case "tool_use":
			return []canonical.TurnEvent{{
				Type: canonical.EventToolCallEnd, ToolCallID: st.ID, ToolName: st.Name,
			}}
		case "thinking":
			// st.Name was repurposed to carry the signature in
			// signature_delta above. Empty when no signature came.
			return []canonical.TurnEvent{{
				Type: canonical.EventThinkingEnd, Signature: st.Name,
			}}
		}
		return nil

	case "message_delta":
		// Carries stop_reason + cumulative usage.
		if ev.Delta != nil && ev.Delta.StopReason != "" {
			t.finalReason = canonicalStopReason(ev.Delta.StopReason)
		}
		if ev.Usage != nil {
			// message_delta usage is INCREMENTAL on Anthropic; the v4 docs
			// describe it as cumulative across the stream. We just take
			// the last reported values verbatim.
			t.finalUsage = toCanonicalUsage(ev.Usage)
		}
		return nil

	case "message_stop":
		usage := t.finalUsage
		return []canonical.TurnEvent{{
			Type: canonical.EventMessageEnd,
			StopReason: t.finalReason,
			Usage: &usage,
		}}

	case "error":
		msg := "unknown"
		etype := "stream_error"
		if ev.Error != nil {
			msg = ev.Error.Message
			etype = ev.Error.Type
		}
		return []canonical.TurnEvent{{
			Type: canonical.EventError,
			Error: &canonical.ErrorInfo{Code: etype, Message: msg},
		}}
	}
	return nil
}

func canonicalStopReason(s string) canonical.StopReason {
	switch s {
	case "end_turn":
		return canonical.StopEndTurn
	case "max_tokens":
		return canonical.StopMaxTokens
	case "tool_use":
		return canonical.StopToolUse
	case "stop_sequence":
		return canonical.StopStopSequence
	default:
		return canonical.StopReason(s)
	}
}

func toCanonicalUsage(u *anthropic.Usage) canonical.Usage {
	return canonical.Usage{
		InputTokens:      u.InputTokens,
		OutputTokens:     u.OutputTokens,
		CacheReadTokens:  u.CacheReadInputTokens,
		CacheWriteTokens: u.CacheCreationInputTokens,
	}
}