package processor

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"

	lua "github.com/yuin/gopher-lua"

	"modify/logger"
	"modify/utils"
)

type CaptureGroup struct {
	Name    string
	Value   string
	Updated string
	Range   [2]int
}

// ProcessContent applies regex replacement with Lua processing
// The filename here exists ONLY so we can pass it to the lua environment
// It's not used for anything else
func ProcessRegex(content string, command utils.ModifyCommand, filename string) ([]utils.ReplaceCommand, error) {
	var commands []utils.ReplaceCommand
	logger.Trace("Processing regex: %q", command.Regex)

	// Start timing the regex processing
	startTime := time.Now()

	// We don't HAVE to do this multiple times for a pattern
	// But it's quick enough for us to not care
	pattern := resolveRegexPlaceholders(command.Regex)
	logger.Debug("Compiling regex pattern: %s", pattern)

	patternCompileStart := time.Now()
	compiledPattern, err := regexp.Compile(pattern)
	if err != nil {
		logger.Error("Error compiling pattern: %v", err)
		return commands, fmt.Errorf("error compiling pattern: %v", err)
	}
	logger.Debug("Compiled pattern successfully in %v: %s", time.Since(patternCompileStart), pattern)

	// Same here, it's just string concatenation, it won't kill us
	// More important is that we don't fuck up the command
	// But we shouldn't be able to since it's passed by value
	previous := command.Lua
	luaExpr := BuildLuaScript(command.Lua)
	logger.Debug("Transformed Lua expression: %q → %q", previous, luaExpr)

	// Process all regex matches
	matchFindStart := time.Now()
	indices := compiledPattern.FindAllStringSubmatchIndex(content, -1)
	matchFindDuration := time.Since(matchFindStart)

	logger.Debug("Found %d matches in content of length %d (search took %v)",
		len(indices), len(content), matchFindDuration)

	// Log pattern complexity metrics
	patternComplexity := estimatePatternComplexity(pattern)
	logger.Debug("Pattern complexity estimate: %d", patternComplexity)

	if len(indices) == 0 {
		logger.Warning("No matches found for regex: %q", pattern)
		logger.Debug("Total regex processing time: %v", time.Since(startTime))
		return commands, nil
	}

	// We walk backwards because we're replacing something with something else that might be longer
	// And in the case it is longer than the original all indicces past that change will be fucked up
	// By going backwards we fuck up all the indices to the end of the file that we don't care about
	// Because there either aren't any (last match) or they're already modified (subsequent matches)
	for i, matchIndices := range indices {
		logger.Debug("Processing match %d of %d", i+1, len(indices))
		logger.Trace("Match indices: %v (match position %d-%d)", matchIndices, matchIndices[0], matchIndices[1])

		L, err := NewLuaState()
		if err != nil {
			logger.Error("Error creating Lua state: %v", err)
			return commands, fmt.Errorf("error creating Lua state: %v", err)
		}
		L.SetGlobal("file", lua.LString(filename))
		// Hmm... Maybe we don't want to defer this..
		// Maybe we want to close them every iteration
		// We'll leave it as is for now
		defer L.Close()
		logger.Trace("Lua state created successfully for match %d", i+1)

		// Why we're doing this whole song and dance of indices is to properly handle empty matches
		// Plus it's a little cleaner to surgically replace our matches
		// If we were to use string.replace and encountered an empty match there'd be nothing to replace
		// But using indices an empty match would have its starting and ending indices be the same
		// So when we're cutting open the array we say 0:7 + modified + 7:end
		// As if concatenating in the middle of the array
		// Plus it supports lookarounds
		match := content[matchIndices[0]:matchIndices[1]]
		matchPreview := match
		if len(match) > 50 {
			matchPreview = match[:47] + "..."
		}
		logger.Trace("Matched content: %q (length: %d)", matchPreview, len(match))

		groups := matchIndices[2:]
		if len(groups) <= 0 {
			logger.Warning("No capture groups found for match %q and regex %q", matchPreview, pattern)
			continue
		}
		if len(groups)%2 == 1 {
			logger.Warning("Invalid number of group indices (%d), should be even: %v", len(groups), groups)
			continue
		}

		// Count how many valid groups we have
		validGroups := 0
		for j := 0; j < len(groups); j += 2 {
			if groups[j] != -1 && groups[j+1] != -1 {
				validGroups++
			}
		}
		logger.Debug("Found %d valid capture groups in match", validGroups)

		for _, index := range groups {
			if index == -1 {
				logger.Warning("Negative index encountered in match indices %v. This may indicate an issue with the regex pattern or an empty/optional capture group.", matchIndices)
				continue
			}
		}

		// We have to use array to preserve order
		// Very important for the reconstruction step
		// Because we must overwrite the values in reverse order
		// See comments a few dozen lines above for more details
		captureGroups := make([]*CaptureGroup, 0, len(groups)/2)
		groupNames := compiledPattern.SubexpNames()[1:]
		for i, name := range groupNames {
			start := groups[i*2]
			end := groups[i*2+1]
			if start == -1 || end == -1 {
				continue
			}

			value := content[start:end]
			captureGroups = append(captureGroups, &CaptureGroup{
				Name:  name,
				Value: value,
				Range: [2]int{start, end},
			})

			// Include name info in log if available
			if name != "" {
				logger.Trace("Capture group '%s': %q (pos %d-%d)", name, value, start, end)
			} else {
				logger.Trace("Capture group #%d: %q (pos %d-%d)", i+1, value, start, end)
			}
		}

		// Use the DeduplicateGroups flag to control whether to deduplicate capture groups
		if !command.NoDedup {
			logger.Debug("Deduplicating capture groups as specified in command settings")
			captureGroups = deduplicateGroups(captureGroups)
		}

		if err := toLua(L, captureGroups); err != nil {
			logger.Error("Failed to set Lua variables: %v", err)
			continue
		}
		logger.Trace("Set %d capture groups as Lua variables", len(captureGroups))

		if err := L.DoString(luaExpr); err != nil {
			logger.Error("Lua script execution failed: %v\nScript: %s\nCapture Groups: %+v",
				err, luaExpr, captureGroups)
			continue
		}
		logger.Trace("Lua script executed successfully")

		// Get modifications from Lua
		captureGroups, err = fromLua(L, captureGroups)
		if err != nil {
			logger.Error("Failed to retrieve modifications from Lua: %v", err)
			continue
		}
		logger.Trace("Retrieved updated values from Lua")

		replacement := ""
		replacementVar := L.GetGlobal("replacement")
		if replacementVar.Type() != lua.LTNil {
			replacement = replacementVar.String()
			logger.Debug("Using global replacement: %q", replacement)
		}

		// Check if modification flag is set
		modifiedVal := L.GetGlobal("modified")
		if modifiedVal.Type() != lua.LTBool || !lua.LVAsBool(modifiedVal) {
			logger.Debug("Skipping match - no modifications made by Lua script")
			continue
		}

		if replacement == "" {
			// Apply the modifications to the original match
			replacement = match

			// Count groups that were actually modified
			modifiedGroups := 0
			for _, capture := range captureGroups {
				if capture.Value != capture.Updated {
					modifiedGroups++
				}
			}
			logger.Info("%d of %d capture groups identified for modification", modifiedGroups, len(captureGroups))

			for _, capture := range captureGroups {
				if capture.Value == capture.Updated {
					logger.Info("Capture group unchanged: %s", LimitString(capture.Value, 50))
					continue
				}

				// Log what changed with context
				logger.Debug("Capture group %s scheduled for modification: %q → %q",
					capture.Name, capture.Value, capture.Updated)

				// Indices of the group are relative to content
				// To relate them to match we have to subtract the match start index
				// replacement = replacement[:groupStart] + newVal + replacement[groupEnd:]
				commands = append(commands, utils.ReplaceCommand{
					From: capture.Range[0],
					To:   capture.Range[1],
					With: capture.Updated,
				})
			}
		} else {
			commands = append(commands, utils.ReplaceCommand{
				From: matchIndices[0],
				To:   matchIndices[1],
				With: replacement,
			})
		}
	}

	logger.Debug("Total regex processing time: %v", time.Since(startTime))
	return commands, nil
}

func deduplicateGroups(captureGroups []*CaptureGroup) []*CaptureGroup {
	deduplicatedGroups := make([]*CaptureGroup, 0)
	for _, group := range captureGroups {
		overlaps := false
		logger.Debug("Checking capture group: %s with range %v", group.Name, group.Range)
		for _, existingGroup := range deduplicatedGroups {
			logger.Debug("Comparing with existing group: %s with range %v", existingGroup.Name, existingGroup.Range)
			if group.Range[0] < existingGroup.Range[1] && group.Range[1] > existingGroup.Range[0] {
				overlaps = true
				logger.Warning("Detected overlap between capture group '%s' and existing group '%s' in range %v-%v and %v-%v", group.Name, existingGroup.Name, group.Range[0], group.Range[1], existingGroup.Range[0], existingGroup.Range[1])
				break
			}
		}
		if overlaps {
			// We CAN just continue despite this fuckup
			logger.Warning("Overlapping capture group: %s", group.Name)
			continue
		}
		logger.Debug("No overlap detected for capture group: %s. Adding to deduplicated groups.", group.Name)
		deduplicatedGroups = append(deduplicatedGroups, group)
	}
	return deduplicatedGroups
}

// The order of these replaces is important
// This one handles !num-s inside of named capture groups
// If it were not here our !num in a named capture group would
// Expand to another capture group in the capture group
// We really only want one (our named) capture group
func resolveRegexPlaceholders(pattern string) string {
	// Handle special pattern modifications
	if !strings.HasPrefix(pattern, "(?s)") {
		pattern = "(?s)" + pattern
	}

	namedGroupNum := regexp.MustCompile(`(?:(\?<[^>]+>)(!num))`)
	pattern = namedGroupNum.ReplaceAllStringFunc(pattern, func(match string) string {
		parts := namedGroupNum.FindStringSubmatch(match)
		if len(parts) != 3 {
			return match
		}
		replacement := `-?\d*\.?\d+`
		return parts[1] + replacement
	})
	pattern = strings.ReplaceAll(pattern, "!num", `(-?\d*\.?\d+)`)
	pattern = strings.ReplaceAll(pattern, "!any", `.*?`)
	repPattern := regexp.MustCompile(`!rep\(([^,]+),\s*(\d+)\)`)
	// !rep(pattern, count) repeats the pattern n times
	// Inserting !any between each repetition
	pattern = repPattern.ReplaceAllStringFunc(pattern, func(match string) string {
		parts := repPattern.FindStringSubmatch(match)
		if len(parts) != 3 {
			return match
		}
		repeatedPattern := parts[1]
		count := parts[2]
		repetitions, _ := strconv.Atoi(count)
		return strings.Repeat(repeatedPattern+".*?", repetitions-1) + repeatedPattern
	})
	return pattern
}

// ToLua sets capture groups as Lua variables (v1, v2, etc. for numeric values and s1, s2, etc. for strings)
func toLua(L *lua.LState, data interface{}) error {
	captureGroups, ok := data.([]*CaptureGroup)
	if !ok {
		return fmt.Errorf("expected []*CaptureGroup for captures, got %T", data)
	}

	groupindex := 0
	for _, capture := range captureGroups {
		if capture.Name == "" {
			// We don't want to change the name of the capture group
			// Even if it's empty
			tempName := fmt.Sprintf("%d", groupindex+1)
			groupindex++

			L.SetGlobal("s"+tempName, lua.LString(capture.Value))

			val, err := strconv.ParseFloat(capture.Value, 64)
			if err == nil {
				L.SetGlobal("v"+tempName, lua.LNumber(val))
			}
		} else {
			val, err := strconv.ParseFloat(capture.Value, 64)
			if err == nil {
				L.SetGlobal(capture.Name, lua.LNumber(val))
			} else {
				L.SetGlobal(capture.Name, lua.LString(capture.Value))
			}
		}
	}

	return nil
}

// FromLua implements the Processor interface for RegexProcessor
func fromLua(L *lua.LState, captureGroups []*CaptureGroup) ([]*CaptureGroup, error) {
	captureIndex := 0
	for _, capture := range captureGroups {
		if capture.Name == "" {
			capture.Name = fmt.Sprintf("%d", captureIndex+1)

			vVarName := fmt.Sprintf("v%s", capture.Name)
			sVarName := fmt.Sprintf("s%s", capture.Name)
			captureIndex++

			vLuaVal := L.GetGlobal(vVarName)
			sLuaVal := L.GetGlobal(sVarName)

			if sLuaVal.Type() == lua.LTString {
				capture.Updated = sLuaVal.String()
			}
			// Numbers have priority
			if vLuaVal.Type() == lua.LTNumber {
				capture.Updated = vLuaVal.String()
			}
		} else {
			// Easy shit
			capture.Updated = L.GetGlobal(capture.Name).String()
		}
	}

	return captureGroups, nil
}

// estimatePatternComplexity gives a rough estimate of regex pattern complexity
// This can help identify potentially problematic patterns
func estimatePatternComplexity(pattern string) int {
	complexity := len(pattern)

	// Add complexity for potentially expensive operations
	complexity += strings.Count(pattern, ".*") * 10 // Greedy wildcard
	complexity += strings.Count(pattern, ".*?") * 5 // Non-greedy wildcard
	complexity += strings.Count(pattern, "[^") * 3  // Negated character class
	complexity += strings.Count(pattern, "\\b") * 2 // Word boundary
	complexity += strings.Count(pattern, "(") * 2   // Capture groups
	complexity += strings.Count(pattern, "(?:") * 1 // Non-capture groups
	complexity += strings.Count(pattern, "\\1") * 3 // Backreferences
	complexity += strings.Count(pattern, "{") * 2   // Counted repetition

	return complexity
}