system({
    title: "Generates concise file diffs.",
    lineNumbers: true,
})

export default function (ctx: ChatGenerationContext) {
    const { $ } = ctx

    $`## DIFF file format

The DIFF format should be used to generate diff changes on large files with small number of changes: 

- existing lines must start with their original line number: [<line number>] <line>
- deleted lines MUST start with - followed by the line number: - [<line number>] <deleted line>
- added lines MUST start with +, no line number: + <added line>
- deleted lines MUST exist in the original file (do not invent deleted lines)
- added lines MUST not exist in the original file

### Guidance:

- each line in the source starts with a line number: [line] <line>
- preserve indentation
- use relative file path name
- emit original line numbers from existing lines and deleted lines
- only generate diff for files that have changes
- only emit a couple unmodified lines before and after the changes
- keep the diffs AS SMALL AS POSSIBLE
- when reading files, ask for line numbers
- minimize the number of unmodified lines. DO NOT EMIT MORE THEN 2 UNMODIFIED LINES BEFORE AND AFTER THE CHANGES. Otherwise use the FILE file format.

- do NOT generate diff for files that have no changes
- do NOT emit diff if lines are the same
- do NOT emit the whole file content
- do NOT emit line numbers for added lines
- do NOT use <, > or --- in the diff syntax

- Use one DIFF section per change.

### Examples:

FOLLOW THE SYNTAX PRECISLY. THIS IS IMPORTANT.
DIFF ./file.ts:
\`\`\`diff
[original line number]  line before changes
- [original line number] <deleted line>
+ <added line>
[original line number]  line after changes
\`\`\`

DIFF ./file2.ts:
\`\`\`diff
[original line number]  line before changes
- [original line number] <deleted line>
- [original line number] <delete line 2>
+ <added line>
+ <added line 2>
[original line number]  line after changes
\`\`\`

DIFF ./file3.ts:
\`\`\`diff
[original line number]  line before changes
+ <added line>
[original line number]  line after changes
\`\`\`

DIFF ./file4.ts:
\`\`\`diff
[original line number]  line before changes
- [original line number] <deleted line>
[original line number]  line after changes
\`\`\`

## Choosing what file format to use

- If the file content is large (> 50 lines) and the changes are small, use the DIFF format.
- In all other cases, use the FILE file format.
`
}