Add vendor assessment agent

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/agent/tools/search/diff_documents.go

@@ -0,0 +1,156 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package search
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"go.probo.inc/probo/pkg/agent"
+)
+
+type (
+	diffParams struct {
+		TextA  string `json:"text_a" jsonschema:"The first document text to compare"`
+		TextB  string `json:"text_b" jsonschema:"The second document text to compare"`
+		LabelA string `json:"label_a" jsonschema:"Label for the first document (e.g. 'current version')"`
+		LabelB string `json:"label_b" jsonschema:"Label for the second document (e.g. 'archived version')"`
+	}
+
+	diffResult struct {
+		HasDifferences bool   `json:"has_differences"`
+		UnifiedDiff    string `json:"unified_diff,omitempty"`
+		AddedLines     int    `json:"added_lines"`
+		RemovedLines   int    `json:"removed_lines"`
+		ErrorDetail    string `json:"error_detail,omitempty"`
+	}
+)
+
+const (
+	maxDiffOutput = 16000
+)
+
+func DiffDocumentsTool() agent.Tool {
+	return agent.FunctionTool(
+		"diff_documents",
+		"Compare two document texts and return a unified diff showing the differences. Useful for comparing current vs. archived versions of privacy policies, terms of service, or other legal documents.",
+		func(ctx context.Context, p diffParams) (agent.ToolResult, error) {
+			labelA := p.LabelA
+			if labelA == "" {
+				labelA = "document_a"
+			}
+			labelB := p.LabelB
+			if labelB == "" {
+				labelB = "document_b"
+			}
+
+			linesA := strings.Split(p.TextA, "\n")
+			linesB := strings.Split(p.TextB, "\n")
+
+			diff := computeDiff(linesA, linesB, labelA, labelB)
+
+			if diff.tooLarge {
+				return agent.ResultJSON(diffResult{
+					HasDifferences: true,
+					ErrorDetail:    diff.output,
+				}), nil
+			}
+
+			result := diffResult{
+				HasDifferences: diff.added > 0 || diff.removed > 0,
+				AddedLines:     diff.added,
+				RemovedLines:   diff.removed,
+			}
+
+			if result.HasDifferences {
+				output := diff.output
+				if len(output) > maxDiffOutput {
+					output = output[:maxDiffOutput] + "\n[... diff truncated]"
+				}
+				result.UnifiedDiff = output
+			}
+
+			return agent.ResultJSON(result), nil
+		},
+	)
+}
+
+type (
+	diffOutput struct {
+		output   string
+		added    int
+		removed  int
+		tooLarge bool
+	}
+)
+
+func computeDiff(linesA, linesB []string, labelA, labelB string) diffOutput {
+	// Simple line-by-line LCS-based diff.
+	m, n := len(linesA), len(linesB)
+
+	// Build LCS table (bounded to prevent excessive memory for very large docs).
+	if m > 5000 || n > 5000 {
+		return diffOutput{
+			output:   "documents too large for detailed diff (limit 5000 lines per side)",
+			tooLarge: true,
+		}
+	}
+
+	// LCS length table.
+	dp := make([][]int, m+1)
+	for i := range dp {
+		dp[i] = make([]int, n+1)
+	}
+	for i := m - 1; i >= 0; i-- {
+		for j := n - 1; j >= 0; j-- {
+			if linesA[i] == linesB[j] {
+				dp[i][j] = dp[i+1][j+1] + 1
+			} else if dp[i+1][j] >= dp[i][j+1] {
+				dp[i][j] = dp[i+1][j]
+			} else {
+				dp[i][j] = dp[i][j+1]
+			}
+		}
+	}
+
+	// Walk the LCS table to produce diff hunks.
+	var sb strings.Builder
+	fmt.Fprintf(&sb, "--- %s\n+++ %s\n", labelA, labelB)
+
+	var added, removed int
+	i, j := 0, 0
+	for i < m || j < n {
+		if i < m && j < n && linesA[i] == linesB[j] {
+			// Context line — only emit near changes.
+			i++
+			j++
+		} else if j < n && (i >= m || dp[i][j+1] >= dp[i+1][j]) {
+			sb.WriteString("+ " + linesB[j] + "\n")
+			added++
+			j++
+		} else if i < m {
+			sb.WriteString("- " + linesA[i] + "\n")
+			removed++
+			i++
+		}
+	}
+
+	return diffOutput{
+		output:  sb.String(),
+		added:   added,
+		removed: removed,
+	}
+}