package acp

import (
	"encoding/json"
	"strings"
	"unicode/utf8"

	"albedo/cli/internal/daemon"
)

const toolDisplayLimit = 256 * 1024
const toolTruncationMarker = "[albedo: tool output truncated to fit 256 KiB]"

// toolDisplay is shared by durable live events and hydrated history rows.
func toolDisplay(event daemon.StreamEvent) map[string]any {
	title := event.ToolTitle
	if title == "" {
		title = event.ToolName
	}
	update := map[string]any{"sessionUpdate": "tool_call_update", "toolCallId": event.ProgressCallID, "status": event.ToolStatus, "title": title, "kind": "other", "rawInput": event.ToolArgs, "rawOutput": map[string]string{"result": event.ToolResult}}
	content := []any{textContent(event.ToolResult)}
	locations := []map[string]string{}
	seen := map[string]bool{}
	addLocation := func(path string) {
		if path != "" && !seen[path] {
			locations = append(locations, map[string]string{"path": path})
			seen[path] = true
		}
	}
	evidence := map[string]bool{}
	if trace := event.ToolTrace; trace != nil {
		for _, activity := range trace.Activities {
			evidence[activity.Kind] = true
			if activity.Kind == "read" {
				addLocation(activity.Target)
			}
		}
		for _, change := range trace.Changes {
			evidence["edit"] = true
			addLocation(change.Path)
			if change.Kind == "diff" && change.NewText != nil {
				content = append(content, map[string]any{"type": "diff", "path": change.Path, "oldText": change.OldText, "newText": *change.NewText})
			} else {
				reason := change.Reason
				if reason == "" {
					reason = "file snapshots unavailable"
				}
				text := change.Path + ": " + reason
				if change.Diff != "" {
					text += "\nUnified diff:\n" + change.Diff
				}
				content = append(content, textContent(text))
			}
		}
	}
	if len(evidence) == 1 {
		for kind := range evidence {
			if mapped, ok := map[string]string{"edit": "edit", "read": "read", "search": "search", "run": "execute", "web": "fetch"}[kind]; ok {
				update["kind"] = mapped
			}
		}
	}
	update["content"] = content
	update["locations"] = locations
	encoded, _ := json.Marshal(update)
	if len(encoded) <= toolDisplayLimit {
		return update
	}
	// Drop indivisible snapshots and oversized input before shortening result text.
	// The marker makes every loss visible, including JSON escaping expansion.
	input, _ := json.Marshal(event.ToolArgs)
	if len(input) > toolDisplayLimit/4 {
		delete(update, "rawInput")
	}
	encodedLocations, _ := json.Marshal(locations)
	if len(encodedLocations) > toolDisplayLimit/4 {
		delete(update, "locations")
	}
	update["title"] = boundedText(title, 4096)
	text := event.ToolResult
	for {
		update["content"] = []any{textContent(text + "\n" + toolTruncationMarker)}
		update["rawOutput"] = map[string]string{"result": text}
		encoded, _ = json.Marshal(update)
		if len(encoded) <= toolDisplayLimit {
			return update
		}
		text = boundedText(text, len(text)/2)
	}
}

func textContent(text string) map[string]any {
	return map[string]any{"type": "content", "content": map[string]string{"type": "text", "text": text}}
}

func boundedText(text string, limit int) string {
	if len(text) <= limit {
		return text
	}
	text = text[:limit]
	for !utf8.ValidString(text) {
		text = strings.TrimSuffix(text, text[len(text)-1:])
	}
	return text
}