---@meta

--- Optional parameters:
--- @class vim.diff.Opts
--- @inlinedoc
---
--- Invoked for each hunk in the diff. Return a negative number
--- to cancel the callback for any remaining hunks.
--- Arguments:
---   - `start_a` (`integer`): Start line of hunk in {a}.
---   - `count_a` (`integer`): Hunk size in {a}.
---   - `start_b` (`integer`): Start line of hunk in {b}.
---   - `count_b` (`integer`): Hunk size in {b}.
--- @field on_hunk fun(start_a: integer, count_a: integer, start_b: integer, count_b: integer): integer
---
--- Form of the returned diff:
---   - `unified`: String in unified format.
---   - `indices`: Array of hunk locations.
--- Note: This option is ignored if `on_hunk` is used.
--- (default: `'unified'`)
--- @field result_type 'unified'|'indices'
---
--- Run linematch on the resulting hunks from xdiff. When integer, only hunks
--- upto this size in lines are run through linematch.
--- Requires `result_type = indices`, ignored otherwise.
--- @field linematch boolean|integer
---
--- Diff algorithm to use. Values:
---   - `myers`: the default algorithm
---   - `minimal`: spend extra time to generate the smallest possible diff
---   - `patience`: patience diff algorithm
---   - `histogram`: histogram diff algorithm
--- (default: `'myers'`)
--- @field algorithm 'myers'|'minimal'|'patience'|'histogram'
--- @field ctxlen integer Context length
--- @field interhunkctxlen integer Inter hunk context length
--- @field ignore_whitespace boolean Ignore whitespace
--- @field ignore_whitespace_change boolean Ignore whitespace change
--- @field ignore_whitespace_change_at_eol boolean Ignore whitespace change at end-of-line.
--- @field ignore_cr_at_eol boolean Ignore carriage return at end-of-line
--- @field ignore_blank_lines boolean Ignore blank lines
--- @field indent_heuristic boolean Use the indent heuristic for the internal diff library.

-- luacheck: no unused args

--- Run diff on strings {a} and {b}. Any indices returned by this function,
--- either directly or via callback arguments, are 1-based.
---
--- Examples:
---
--- ```lua
--- vim.diff('a\n', 'b\nc\n')
--- -- =>
--- -- @@ -1 +1,2 @@
--- -- -a
--- -- +b
--- -- +c
---
--- vim.diff('a\n', 'b\nc\n', {result_type = 'indices'})
--- -- =>
--- -- {
--- --   {1, 1, 1, 2}
--- -- }
--- ```
---
---@param a string First string to compare
---@param b string Second string to compare
---@param opts vim.diff.Opts
---@return string|integer[][]?
---     See {opts.result_type}. `nil` if {opts.on_hunk} is given.
function vim.diff(a, b, opts) end