package api

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"time"

	"github.com/thepeterstone/claudomator/internal/storage"
	"github.com/thepeterstone/claudomator/internal/task"
)

// logStore is the minimal storage interface needed by handleStreamLogs.
type logStore interface {
	GetExecution(id string) (*storage.Execution, error)
}

// taskLogStore is the minimal storage interface needed by handleStreamTaskLogs.
type taskLogStore interface {
	GetExecution(id string) (*storage.Execution, error)
	GetLatestExecution(taskID string) (*storage.Execution, error)
}

const maxTailDuration = 30 * time.Minute

var terminalStates = map[string]bool{
	string(task.StateCompleted):      true,
	string(task.StateFailed):         true,
	string(task.StateTimedOut):       true,
	string(task.StateCancelled):      true,
	string(task.StateBudgetExceeded): true,
}

type logStreamMsg struct {
	Type    string        `json:"type"`
	Message *logAssistMsg `json:"message,omitempty"`
	CostUSD float64       `json:"cost_usd,omitempty"`
}

type logAssistMsg struct {
	Content []logContentBlock `json:"content"`
}

type logContentBlock struct {
	Type  string          `json:"type"`
	Text  string          `json:"text,omitempty"`
	Name  string          `json:"name,omitempty"`
	Input json.RawMessage `json:"input,omitempty"`
}

// handleStreamTaskLogs streams the latest execution log for a task via SSE.
// GET /api/tasks/{id}/logs/stream
func (s *Server) handleStreamTaskLogs(w http.ResponseWriter, r *http.Request) {
	taskID := r.PathValue("id")
	exec, err := s.taskLogStore.GetLatestExecution(taskID)
	if err != nil {
		http.Error(w, "task not found", http.StatusNotFound)
		return
	}

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("X-Accel-Buffering", "no")

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming not supported", http.StatusInternalServerError)
		return
	}

	ctx := r.Context()

	if terminalStates[exec.Status] {
		if exec.StdoutPath != "" {
			if f, err := os.Open(exec.StdoutPath); err == nil {
				defer f.Close()
				var offset int64
				for _, line := range readNewLines(f, &offset) {
					select {
					case <-ctx.Done():
						return
					default:
					}
					emitLogLine(w, flusher, line)
				}
			}
		}
	} else if exec.Status == string(task.StateRunning) {
		tailRunningExecution(ctx, w, flusher, s.taskLogStore, exec)
		return
	}

	fmt.Fprintf(w, "event: done\ndata: {}\n\n")
	flusher.Flush()
}

// handleStreamLogs streams parsed execution log content via SSE.
// GET /api/executions/{id}/logs/stream
func (s *Server) handleStreamLogs(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	exec, err := s.logStore.GetExecution(id)
	if err != nil {
		http.Error(w, "execution not found", http.StatusNotFound)
		return
	}

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("X-Accel-Buffering", "no")

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming not supported", http.StatusInternalServerError)
		return
	}

	ctx := r.Context()

	if terminalStates[exec.Status] {
		if exec.StdoutPath != "" {
			if f, err := os.Open(exec.StdoutPath); err == nil {
				defer f.Close()
				var offset int64
				for _, line := range readNewLines(f, &offset) {
					select {
					case <-ctx.Done():
						return
					default:
					}
					emitLogLine(w, flusher, line)
				}
			}
		}
	} else if exec.Status == string(task.StateRunning) {
		tailRunningExecution(ctx, w, flusher, s.logStore, exec)
		return // tailRunningExecution sends the done event
	}

	fmt.Fprintf(w, "event: done\ndata: {}\n\n")
	flusher.Flush()
}

// tailRunningExecution live-tails the stdout log for a RUNNING execution, polling every 250ms.
// It returns when the execution transitions to a terminal state, the context is cancelled,
// or after maxTailDuration (safety guard against goroutine leaks).
func tailRunningExecution(ctx context.Context, w http.ResponseWriter, flusher http.Flusher, store logStore, exec *storage.Execution) {
	var (
		f      *os.File
		offset int64
	)

	// Emit any content already written to the log file.
	if exec.StdoutPath != "" {
		var err error
		f, err = os.Open(exec.StdoutPath)
		if err == nil {
			defer f.Close()
			for _, line := range readNewLines(f, &offset) {
				select {
				case <-ctx.Done():
					return
				default:
				}
				emitLogLine(w, flusher, line)
			}
		}
	}

	ticker := time.NewTicker(250 * time.Millisecond)
	defer ticker.Stop()
	deadline := time.NewTimer(maxTailDuration)
	defer deadline.Stop()

	for {
		select {
		case <-ctx.Done():
			return
		case <-deadline.C:
			fmt.Fprintf(w, "event: done\ndata: {}\n\n")
			flusher.Flush()
			return
		case <-ticker.C:
			// If the log file wasn't open yet, try now (may have been created since).
			if f == nil && exec.StdoutPath != "" {
				var err error
				f, err = os.Open(exec.StdoutPath)
				if err != nil {
					f = nil
				} else {
					defer f.Close()
				}
			}

			// Emit any new complete lines.
			if f != nil {
				for _, line := range readNewLines(f, &offset) {
					emitLogLine(w, flusher, line)
				}
			}

			// Re-fetch execution status from DB.
			updated, err := store.GetExecution(exec.ID)
			if err != nil {
				fmt.Fprintf(w, "event: done\ndata: {}\n\n")
				flusher.Flush()
				return
			}
			if terminalStates[updated.Status] {
				// Flush any remaining content written between the last read and now.
				if f != nil {
					for _, line := range readNewLines(f, &offset) {
						emitLogLine(w, flusher, line)
					}
				}
				fmt.Fprintf(w, "event: done\ndata: {}\n\n")
				flusher.Flush()
				return
			}
		}
	}
}

// readNewLines reads all complete lines from f starting at *offset.
// It advances *offset past the last newline so partial trailing lines
// are deferred to the next call (safe for live-tailing growing files).
func readNewLines(f *os.File, offset *int64) [][]byte {
	if _, err := f.Seek(*offset, io.SeekStart); err != nil {
		return nil
	}
	data, err := io.ReadAll(f)
	if err != nil || len(data) == 0 {
		return nil
	}
	lastNL := bytes.LastIndexByte(data, '\n')
	if lastNL < 0 {
		return nil // no complete line yet
	}
	*offset += int64(lastNL + 1)
	return bytes.Split(data[:lastNL], []byte("\n"))
}

// emitLogLine parses a single stream-json line and emits corresponding SSE events.
func emitLogLine(w http.ResponseWriter, flusher http.Flusher, line []byte) {
	if len(line) == 0 {
		return
	}
	var msg logStreamMsg
	if err := json.Unmarshal(line, &msg); err != nil {
		return
	}
	switch msg.Type {
	case "assistant":
		if msg.Message == nil {
			return
		}
		for _, block := range msg.Message.Content {
			var event map[string]string
			switch block.Type {
			case "text":
				event = map[string]string{"type": "text", "content": block.Text}
			case "tool_use":
				summary := string(block.Input)
				if len(summary) > 80 {
					summary = summary[:80]
				}
				event = map[string]string{"type": "tool_use", "content": fmt.Sprintf("%s(%s)", block.Name, summary)}
			default:
				continue
			}
			data, _ := json.Marshal(event)
			fmt.Fprintf(w, "data: %s\n\n", data)
			flusher.Flush()
		}
	case "result":
		event := map[string]string{
			"type":    "cost",
			"content": fmt.Sprintf("%g", msg.CostUSD),
		}
		data, _ := json.Marshal(event)
		fmt.Fprintf(w, "data: %s\n\n", data)
		flusher.Flush()
	}
}