import { DiffStrategy, DiffResult } from "../types"
import { addLineNumbers, everyLineHasLineNumbers, stripLineNumbers } from "../../../integrations/misc/extract-text"

const BUFFER_LINES = 20; // Number of extra context lines to show before and after matches

function levenshteinDistance(a: string, b: string): number {
    const matrix: number[][] = [];

    // Initialize matrix
    for (let i = 0; i <= a.length; i++) {
        matrix[i] = [i];
    }
    for (let j = 0; j <= b.length; j++) {
        matrix[0][j] = j;
    }

    // Fill matrix
    for (let i = 1; i <= a.length; i++) {
        for (let j = 1; j <= b.length; j++) {
            if (a[i-1] === b[j-1]) {
                matrix[i][j] = matrix[i-1][j-1];
            } else {
                matrix[i][j] = Math.min(
                    matrix[i-1][j-1] + 1, // substitution
                    matrix[i][j-1] + 1,   // insertion
                    matrix[i-1][j] + 1    // deletion
                );
            }
        }
    }

    return matrix[a.length][b.length];
}

function getSimilarity(original: string, search: string): number {
    if (search === '') {
        return 1;
    }

    // Normalize strings by removing extra whitespace but preserve case
    const normalizeStr = (str: string) => str.replace(/\s+/g, ' ').trim();
    
    const normalizedOriginal = normalizeStr(original);
    const normalizedSearch = normalizeStr(search);
    
    if (normalizedOriginal === normalizedSearch) { return 1; }
    
    // Calculate Levenshtein distance
    const distance = levenshteinDistance(normalizedOriginal, normalizedSearch);
    
    // Calculate similarity ratio (0 to 1, where 1 is exact match)
    const maxLength = Math.max(normalizedOriginal.length, normalizedSearch.length);
    return 1 - (distance / maxLength);
}

export class SearchReplaceDiffStrategy implements DiffStrategy {
    private fuzzyThreshold: number;
    private bufferLines: number;

    constructor(fuzzyThreshold?: number, bufferLines?: number) {
        // Use provided threshold or default to exact matching (1.0)
        // Note: fuzzyThreshold is inverted in UI (0% = 1.0, 10% = 0.9)
        // so we use it directly here
        this.fuzzyThreshold = fuzzyThreshold ?? 1.0;
        this.bufferLines = bufferLines ?? BUFFER_LINES;
    }

    getToolDescription(args: { cwd: string; toolOptions?: { [key: string]: string } }): string {
        return `## apply_diff
Description: Request to replace existing code using a search and replace block.
This tool allows for precise, surgical replaces to files by specifying exactly what content to search for and what to replace it with.
The tool will maintain proper indentation and formatting while making changes.
Only a single operation is allowed per tool use.
The SEARCH section must exactly match existing content including whitespace and indentation.
If you're not confident in the exact content to search for, use the read_file tool first to get the exact content.
When applying the diffs, be extra careful to remember to change any closing brackets or other syntax that may be affected by the diff farther down in the file.

Parameters:
- path: (required) The path of the file to modify (relative to the current working directory ${args.cwd})
- diff: (required) The search/replace block defining the changes.
- start_line: (required) The line number where the search block starts.
- end_line: (required) The line number where the search block ends.

Diff format:
\`\`\`
<<<<<<< SEARCH
[exact content to find including whitespace]
=======
[new content to replace with]
>>>>>>> REPLACE
\`\`\`

Example:

Original file:
\`\`\`
1 | def calculate_total(items):
2 |     total = 0
3 |     for item in items:
4 |         total += item
5 |     return total
\`\`\`

Search/Replace content:
\`\`\`
<<<<<<< SEARCH
def calculate_total(items):
    total = 0
    for item in items:
        total += item
    return total
=======
def calculate_total(items):
    """Calculate total with 10% markup"""
    return sum(item * 1.1 for item in items)
>>>>>>> REPLACE
\`\`\`

Usage:
<apply_diff>
<path>File path here</path>
<diff>
Your search/replace content here
</diff>
<start_line>1</start_line>
<end_line>5</end_line>
</apply_diff>`
    }

    async applyDiff(originalContent: string, diffContent: string, startLine?: number, endLine?: number): Promise<DiffResult> {
        // Extract the search and replace blocks
        const match = diffContent.match(/<<<<<<< SEARCH\n([\s\S]*?)\n?=======\n([\s\S]*?)\n?>>>>>>> REPLACE/);
        if (!match) {
            return {
                success: false,
                error: `Invalid diff format - missing required SEARCH/REPLACE sections\n\nDebug Info:\n- Expected Format: <<<<<<< SEARCH\\n[search content]\\n=======\\n[replace content]\\n>>>>>>> REPLACE\n- Tip: Make sure to include both SEARCH and REPLACE sections with correct markers`
            };
        }

        let [_, searchContent, replaceContent] = match;

        // Detect line ending from original content
        const lineEnding = originalContent.includes('\r\n') ? '\r\n' : '\n';

        // Strip line numbers from search and replace content if every line starts with a line number
        if (everyLineHasLineNumbers(searchContent) && everyLineHasLineNumbers(replaceContent)) {
            searchContent = stripLineNumbers(searchContent);
            replaceContent = stripLineNumbers(replaceContent);
        }
        
        // Split content into lines, handling both \n and \r\n
        const searchLines = searchContent === '' ? [] : searchContent.split(/\r?\n/);
        const replaceLines = replaceContent === '' ? [] : replaceContent.split(/\r?\n/);
        const originalLines = originalContent.split(/\r?\n/);

        // Validate that empty search requires start line
        if (searchLines.length === 0 && !startLine) {
            return {
                success: false,
                error: `Empty search content requires start_line to be specified\n\nDebug Info:\n- Empty search content is only valid for insertions at a specific line\n- For insertions, specify the line number where content should be inserted`
            };
        }

        // Validate that empty search requires same start and end line
        if (searchLines.length === 0 && startLine && endLine && startLine !== endLine) {
            return {
                success: false,
                error: `Empty search content requires start_line and end_line to be the same (got ${startLine}-${endLine})\n\nDebug Info:\n- Empty search content is only valid for insertions at a specific line\n- For insertions, use the same line number for both start_line and end_line`
            };
        }
        
        // Initialize search variables
        let matchIndex = -1;
        let bestMatchScore = 0;
        let bestMatchContent = "";
        const searchChunk = searchLines.join('\n');

        // Determine search bounds
        let searchStartIndex = 0;
        let searchEndIndex = originalLines.length;

        // Validate and handle line range if provided
        if (startLine && endLine) {
            // Convert to 0-based index
            const exactStartIndex = startLine - 1;
            const exactEndIndex = endLine - 1;

            if (exactStartIndex < 0 || exactEndIndex > originalLines.length || exactStartIndex > exactEndIndex) {
                return {
                    success: false,
                    error: `Line range ${startLine}-${endLine} is invalid (file has ${originalLines.length} lines)\n\nDebug Info:\n- Requested Range: lines ${startLine}-${endLine}\n- File Bounds: lines 1-${originalLines.length}`,
                };
            }

            // Try exact match first
            const originalChunk = originalLines.slice(exactStartIndex, exactEndIndex + 1).join('\n');
            const similarity = getSimilarity(originalChunk, searchChunk);
            if (similarity >= this.fuzzyThreshold) {
                matchIndex = exactStartIndex;
                bestMatchScore = similarity;
                bestMatchContent = originalChunk;
            } else {
                // Set bounds for buffered search
                searchStartIndex = Math.max(0, startLine - (this.bufferLines + 1));
                searchEndIndex = Math.min(originalLines.length, endLine + this.bufferLines);
            }
        }

        // If no match found yet, try middle-out search within bounds
        if (matchIndex === -1) {
            const midPoint = Math.floor((searchStartIndex + searchEndIndex) / 2);
            let leftIndex = midPoint;
            let rightIndex = midPoint + 1;

            // Search outward from the middle within bounds
            while (leftIndex >= searchStartIndex || rightIndex <= searchEndIndex - searchLines.length) {
                // Check left side if still in range
                if (leftIndex >= searchStartIndex) {
                    const originalChunk = originalLines.slice(leftIndex, leftIndex + searchLines.length).join('\n');
                    const similarity = getSimilarity(originalChunk, searchChunk);
                    if (similarity > bestMatchScore) {
                        bestMatchScore = similarity;
                        matchIndex = leftIndex;
                        bestMatchContent = originalChunk;
                    }
                    leftIndex--;
                }

                // Check right side if still in range
                if (rightIndex <= searchEndIndex - searchLines.length) {
                    const originalChunk = originalLines.slice(rightIndex, rightIndex + searchLines.length).join('\n');
                    const similarity = getSimilarity(originalChunk, searchChunk);
                    if (similarity > bestMatchScore) {
                        bestMatchScore = similarity;
                        matchIndex = rightIndex;
                        bestMatchContent = originalChunk;
                    }
                    rightIndex++;
                }
            }
        }

        // Require similarity to meet threshold
        if (matchIndex === -1 || bestMatchScore < this.fuzzyThreshold) {
            const searchChunk = searchLines.join('\n');
            const originalContentSection = startLine !== undefined && endLine !== undefined
                ? `\n\nOriginal Content:\n${addLineNumbers(
                    originalLines.slice(
                        Math.max(0, startLine - 1 - this.bufferLines),
                        Math.min(originalLines.length, endLine + this.bufferLines)
                    ).join('\n'),
                    Math.max(1, startLine - this.bufferLines)
                )}`
                : `\n\nOriginal Content:\n${addLineNumbers(originalLines.join('\n'))}`;

            const bestMatchSection = bestMatchContent
                ? `\n\nBest Match Found:\n${addLineNumbers(bestMatchContent, matchIndex + 1)}`
                : `\n\nBest Match Found:\n(no match)`;

            const lineRange = startLine || endLine ?
                ` at ${startLine ? `start: ${startLine}` : 'start'} to ${endLine ? `end: ${endLine}` : 'end'}` : '';
            return {
                success: false,
                error: `No sufficiently similar match found${lineRange} (${Math.floor(bestMatchScore * 100)}% similar, needs ${Math.floor(this.fuzzyThreshold * 100)}%)\n\nDebug Info:\n- Similarity Score: ${Math.floor(bestMatchScore * 100)}%\n- Required Threshold: ${Math.floor(this.fuzzyThreshold * 100)}%\n- Search Range: ${startLine && endLine ? `lines ${startLine}-${endLine}` : 'start to end'}\n\nSearch Content:\n${searchChunk}${bestMatchSection}${originalContentSection}`
            };
        }

        // Get the matched lines from the original content
        const matchedLines = originalLines.slice(matchIndex, matchIndex + searchLines.length);
        
        // Get the exact indentation (preserving tabs/spaces) of each line
        const originalIndents = matchedLines.map(line => {
            const match = line.match(/^[\t ]*/);
            return match ? match[0] : '';
        });

        // Get the exact indentation of each line in the search block
        const searchIndents = searchLines.map(line => {
            const match = line.match(/^[\t ]*/);
            return match ? match[0] : '';
        });

        // Apply the replacement while preserving exact indentation
        const indentedReplaceLines = replaceLines.map((line, i) => {
            // Get the matched line's exact indentation
            const matchedIndent = originalIndents[0] || '';
            
            // Get the current line's indentation relative to the search content
            const currentIndentMatch = line.match(/^[\t ]*/);
            const currentIndent = currentIndentMatch ? currentIndentMatch[0] : '';
            const searchBaseIndent = searchIndents[0] || '';
            
            // Calculate the relative indentation level
            const searchBaseLevel = searchBaseIndent.length;
            const currentLevel = currentIndent.length;
            const relativeLevel = currentLevel - searchBaseLevel;
            
            // If relative level is negative, remove indentation from matched indent
            // If positive, add to matched indent
            const finalIndent = relativeLevel < 0
                ? matchedIndent.slice(0, Math.max(0, matchedIndent.length + relativeLevel))
                : matchedIndent + currentIndent.slice(searchBaseLevel);
            
            return finalIndent + line.trim();
        });

        // Construct the final content
        const beforeMatch = originalLines.slice(0, matchIndex);
        const afterMatch = originalLines.slice(matchIndex + searchLines.length);
        
        const finalContent = [...beforeMatch, ...indentedReplaceLines, ...afterMatch].join(lineEnding);
        return {
            success: true,
            content: finalContent
        };
    }
}