package main

import (
	"context"
	"fmt"
	"log/slog"
	"regexp"
	"strings"
	"watch-tool/models"
	"watch-tool/parser"
	"watch-tool/patterns"

	"codeberg.org/pata1704/drain3"
	"github.com/hpcloud/tail"
)

type FileMonitor struct {
	config   ToolConfig
	parser   parser.Parser
	hostname string
}

func NewFileMonitor(config ToolConfig, hostname string, drainCfg *drain3.Config, stateDir string) *FileMonitor {
	var logParser parser.Parser

	pCfg := parser.ParserConfig{
		ServiceName: config.Name,
		LogType:     "custom",
		Hostname:    hostname,
		DrainConfig: drainCfg,
		StateDir:    stateDir,
	}

	if config.Format.Pattern != "" {
		compiledRegex, err := regexp.Compile(config.Format.Pattern)
		if err != nil {
			slog.Error("Invalid regex pattern in tool config", "tool", config.Name, "error", err)
			logParser = parser.NewGenericParser(config.Name, hostname, pCfg.DrainConfig, pCfg.StateDir)

		} else {
			gp := parser.NewGenericParser(config.Name, hostname, pCfg.DrainConfig, pCfg.StateDir)

			customExtractor := patterns.CompiledExtractor{
				Name:    "config_custom_pattern",
				Pattern: compiledRegex,
				Fields:  config.Format.Fields,
			}

			gp.Extractors = append(gp.Extractors, customExtractor)
			logParser = gp
		}
	} else {
		var err error
		logParser, err = parser.New(pCfg)
		if err != nil {
			slog.Error("Cannot get tool specific parser from factory", "error", err)
			logParser = parser.NewGenericParser(config.Name, hostname, pCfg.DrainConfig, pCfg.StateDir)
		}
	}

	return &FileMonitor{
		config:   config,
		parser:   logParser,
		hostname: hostname,
	}
}

func (fm *FileMonitor) Start(ctx context.Context, out chan<- models.LogMessage) error {
	defer fm.parser.Close()
	t, err := tail.TailFile(fm.config.LogFile, tail.Config{
		Follow:    true,
		ReOpen:    true,
		MustExist: false,
		Poll:      true,
		Location:  &tail.SeekInfo{Offset: 0, Whence: 2},
	})
	if err != nil {
		return fmt.Errorf("tail.TailFile: %w", err)
	}
	defer t.Stop()

	slog.Debug("Started tailing file", "file", fm.config.LogFile, "tool", fm.config.Name)

	for {
		select {
		case <-ctx.Done():
			slog.Debug("File monitor stopped", "tool", fm.config.Name)
			return nil
		case line, ok := <-t.Lines:
			if !ok {
				return nil
			}

			if line.Err != nil {
				slog.Error("Error reading log file", "tool", fm.config.Name, "error", line.Err)
				continue
			}

			if strings.TrimSpace(line.Text) == "" {
				continue
			}

			entry, err := fm.parser.Parse(line.Text)
			if err != nil {
				slog.Error("Error parsing log line", "tool", fm.config.Name, "error", err)
			} else {
				if entry.Tool == "" {
					entry.Tool = fm.config.Name
				}
			}

			select {
			case out <- entry:
			case <-ctx.Done():
				return nil
			default:
				slog.Warn("Log-Channel is full, entry dropped", "tool", fm.config.Name)
			}
		}
	}
}