package claude

import (
	"fmt"
	"net/http"
	"strings"
	"time"

	"ds2api/internal/sse"
	streamengine "ds2api/internal/stream"
)

type claudeStreamRuntime struct {
	w        http.ResponseWriter
	rc       *http.ResponseController
	canFlush bool

	model     string
	toolNames []string
	messages  []any

	thinkingEnabled       bool
	searchEnabled         bool
	bufferToolContent     bool
	stripReferenceMarkers bool

	messageID string
	thinking  strings.Builder
	text      strings.Builder

	nextBlockIndex     int
	thinkingBlockOpen  bool
	thinkingBlockIndex int
	textBlockOpen      bool
	textBlockIndex     int
	ended              bool
	upstreamErr        string
}

func newClaudeStreamRuntime(
	w http.ResponseWriter,
	rc *http.ResponseController,
	canFlush bool,
	model string,
	messages []any,
	thinkingEnabled bool,
	searchEnabled bool,
	stripReferenceMarkers bool,
	toolNames []string,
) *claudeStreamRuntime {
	return &claudeStreamRuntime{
		w:                     w,
		rc:                    rc,
		canFlush:              canFlush,
		model:                 model,
		messages:              messages,
		thinkingEnabled:       thinkingEnabled,
		searchEnabled:         searchEnabled,
		bufferToolContent:     len(toolNames) > 0,
		stripReferenceMarkers: stripReferenceMarkers,
		toolNames:             toolNames,
		messageID:             fmt.Sprintf("msg_%d", time.Now().UnixNano()),
		thinkingBlockIndex:    -1,
		textBlockIndex:        -1,
	}
}

func (s *claudeStreamRuntime) onParsed(parsed sse.LineResult) streamengine.ParsedDecision {
	if !parsed.Parsed {
		return streamengine.ParsedDecision{}
	}
	if parsed.ErrorMessage != "" {
		s.upstreamErr = parsed.ErrorMessage
		return streamengine.ParsedDecision{Stop: true, StopReason: streamengine.StopReason("upstream_error")}
	}
	if parsed.Stop {
		return streamengine.ParsedDecision{Stop: true}
	}

	contentSeen := false
	for _, p := range parsed.Parts {
		cleanedText := cleanVisibleOutput(p.Text, s.stripReferenceMarkers)
		if cleanedText == "" {
			continue
		}
		if p.Type != "thinking" && s.searchEnabled && sse.IsCitation(cleanedText) {
			continue
		}
		contentSeen = true

		if p.Type == "thinking" {
			if !s.thinkingEnabled {
				continue
			}
			trimmed := sse.TrimContinuationOverlap(s.thinking.String(), cleanedText)
			if trimmed == "" {
				continue
			}
			s.thinking.WriteString(trimmed)
			s.closeTextBlock()
			if !s.thinkingBlockOpen {
				s.thinkingBlockIndex = s.nextBlockIndex
				s.nextBlockIndex++
				s.send("content_block_start", map[string]any{
					"type":  "content_block_start",
					"index": s.thinkingBlockIndex,
					"content_block": map[string]any{
						"type":     "thinking",
						"thinking": "",
					},
				})
				s.thinkingBlockOpen = true
			}
			s.send("content_block_delta", map[string]any{
				"type":  "content_block_delta",
				"index": s.thinkingBlockIndex,
				"delta": map[string]any{
					"type":     "thinking_delta",
					"thinking": trimmed,
				},
			})
			continue
		}

		trimmed := sse.TrimContinuationOverlap(s.text.String(), cleanedText)
		if trimmed == "" {
			continue
		}
		s.text.WriteString(trimmed)
		if s.bufferToolContent {
			if hasUnclosedCodeFence(s.text.String()) {
				continue
			}
			continue
		}
		s.closeThinkingBlock()
		if !s.textBlockOpen {
			s.textBlockIndex = s.nextBlockIndex
			s.nextBlockIndex++
			s.send("content_block_start", map[string]any{
				"type":  "content_block_start",
				"index": s.textBlockIndex,
				"content_block": map[string]any{
					"type": "text",
					"text": "",
				},
			})
			s.textBlockOpen = true
		}
		s.send("content_block_delta", map[string]any{
			"type":  "content_block_delta",
			"index": s.textBlockIndex,
			"delta": map[string]any{
				"type": "text_delta",
				"text": trimmed,
			},
		})
	}

	return streamengine.ParsedDecision{ContentSeen: contentSeen}
}

func hasUnclosedCodeFence(text string) bool {
	return strings.Count(text, "```")%2 == 1
}