// session_parse — after gemini exits, scan its chat JSONL for tool
// calls and matching function responses. Same shape across native
// gemini tools and MCP tools — id is gemini's full canonical id
// (e.g. "mcp_<server>_<tool>__<server>_<tool>_<ts>_<n>"), name is
// the namespaced tool name, args is a JSON map.

package runner

import (
	"bufio"
	"encoding/json"
	"errors"
	"os"

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

// GeminiToolCall pairs a toolCalls entry with the matching
// functionResponse from a later user line.
type GeminiToolCall struct {
	ID     string
	Name   string
	Args   string // JSON
	Output string // functionResponse.response.output
}

// ParseGeminiToolCalls walks the chat JSONL file once and returns
// every (id, name, args, output) tuple in input order. Pairs without
// a matching functionResponse still appear with Output == "".
func ParseGeminiToolCalls(path string) ([]GeminiToolCall, error) {
	f, err := os.Open(path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil, nil
		}
		return nil, err
	}
	defer f.Close()

	calls := map[string]*GeminiToolCall{}
	var order []string

	sc := bufio.NewScanner(f)
	sc.Buffer(make([]byte, 64*1024), 16*1024*1024)
	for sc.Scan() {
		line := sc.Bytes()
		if len(line) == 0 {
			continue
		}
		var rec map[string]any
		if err := json.Unmarshal(line, &rec); err != nil {
			continue
		}
		// Type "gemini" lines carry toolCalls; type "user" lines may
		// carry functionResponse objects inside content[].
		switch rec["type"] {
		case "gemini":
			for _, tcAny := range asSlice(rec["toolCalls"]) {
				tc, ok := tcAny.(map[string]any)
				if !ok {
					continue
				}
				id, _ := tc["id"].(string)
				if id == "" {
					continue
				}
				c, ok := calls[id]
				if !ok {
					c = &GeminiToolCall{ID: id}
					calls[id] = c
					order = append(order, id)
				}
				c.Name, _ = tc["name"].(string)
				if args, ok := tc["args"]; ok {
					if b, err := json.Marshal(args); err == nil {
						c.Args = string(b)
					}
				}
			}
		case "user":
			for _, ctAny := range asSlice(rec["content"]) {
				ct, ok := ctAny.(map[string]any)
				if !ok {
					continue
				}
				fr, ok := ct["functionResponse"].(map[string]any)
				if !ok {
					continue
				}
				id, _ := fr["id"].(string)
				if id == "" {
					continue
				}
				c, ok := calls[id]
				if !ok {
					c = &GeminiToolCall{ID: id}
					calls[id] = c
					order = append(order, id)
				}
				if fr["name"] != nil {
					c.Name, _ = fr["name"].(string)
				}
				resp, _ := fr["response"].(map[string]any)
				if resp != nil {
					if out, ok := resp["output"].(string); ok {
						c.Output = out
					} else if out, ok := resp["output"]; ok {
						if b, err := json.Marshal(out); err == nil {
							c.Output = string(b)
						}
					}
				}
			}
		}
	}
	if err := sc.Err(); err != nil {
		return nil, err
	}
	out := make([]GeminiToolCall, 0, len(order))
	for _, id := range order {
		out = append(out, *calls[id])
	}
	return out, nil
}

func asSlice(v any) []any {
	if s, ok := v.([]any); ok {
		return s
	}
	return nil
}

// EmitGeminiToolCalls translates the parsed slice into TurnEvents.
func EmitGeminiToolCalls(calls []GeminiToolCall, emit func(canonical.TurnEvent)) {
	for _, c := range calls {
		args := c.Args
		if args == "" {
			args = "{}"
		}
		emit(canonical.TurnEvent{
			Type:        canonical.EventToolCallStart,
			ToolCallID:  c.ID,
			ToolName:    c.Name,
			PartialJSON: args,
		})
		emit(canonical.TurnEvent{
			Type:       canonical.EventToolCallEnd,
			ToolCallID: c.ID,
		})
		emit(canonical.TurnEvent{
			Type: canonical.EventToolResult,
			ToolResult: &canonical.ToolResultBlock{
				Type:      canonical.BlockTypeToolResult,
				ToolUseID: c.ID,
				Content: []canonical.Block{
					canonical.NewTextBlock(c.Output),
				},
			},
		})
	}
}