Implementation of Filters

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/filter/CapCertificateFilter.kt

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+// SPDX-FileCopyrightText: 2023 Heiko Schaefer <heiko@schaefer@name>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.wot.dijkstra.filter
+
+import org.pgpainless.wot.dijkstra.sq.Certification
+import org.pgpainless.wot.dijkstra.sq.Fingerprint
+
+class CapCertificateFilter() : CertificationFilter {
+
+    // A certificate's trust amount will be limited to this amount.
+    private val caps: HashMap<Fingerprint, Int> = hashMapOf()
+
+    override fun cost(c: Certification, values: FilterValues, ignoreRegexps: Boolean): Boolean {
+        caps[c.issuer.fingerprint]?.let {
+            if (it < values.amount) {
+                values.amount = it
+            }
+        }
+
+        return true
+    }
+
+    /**
+     * Add rules for the certificate.
+     *
+     * Any certifications issued by the certificate have their trust
+     * amount limited to `cap`.  If a certificate is capped multiple
+     * times, then the minimum cap is used.
+     */
+    fun cap(cert: Fingerprint, cap: Int) {
+        val current = caps[cert]
+
+        if ((current == null) || (current > cap)) {
+            caps[cert] = cap
+        }
+    }
+}

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/filter/CertificationFilter.kt

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+// SPDX-FileCopyrightText: 2023 Heiko Schaefer <heiko@schaefer@name>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.wot.dijkstra.filter
+
+import org.pgpainless.wot.dijkstra.sq.Certification
+import org.pgpainless.wot.dijkstra.sq.Depth
+import org.pgpainless.wot.dijkstra.sq.RegexSet
+
+/**
+ * Current effective values for `depth`, `amount` and `regexps`.
+ *
+ * `regexps` is optional:
+ * Rewriting the regular expressions may be expensive. By setting regexps to
+ * `null`, the caller can signal that it doesn't care about the regular expressions.
+ */
+data class FilterValues(var depth: Depth, var amount: Int, var regexps: RegexSet?)
+
+/**
+ * A mechanism to filter certifications.
+ *
+ * This function should change the content of `values` in place.
+ * This enables chaining of multiple filters.
+ *
+ * This is particularly useful when evaluating a residual network,
+ * i.e., a network minus the capacity used by a particular path.
+ */
+interface CertificationFilter {
+
+    /**
+     * Filter the certification's parameters.
+     *
+     * If the function returns `false`, the certification should be skipped.
+     */
+    fun cost(c: Certification, values: FilterValues, ignoreRegexps: Boolean): Boolean {
+        return true
+    }
+
+}

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/filter/ChainFilter.kt

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+// SPDX-FileCopyrightText: 2023 Heiko Schaefer <heiko@schaefer@name>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.wot.dijkstra.filter
+
+import org.pgpainless.wot.dijkstra.sq.Certification
+
+/**
+ * A filter that chains multiple filters together.
+ *
+ * The filters are called in the order that they are added. If a
+ * filter returns `false`, then this filter immediately returns
+ * false.
+ */
+class ChainFilter(val filters: MutableList<CertificationFilter>) : CertificationFilter {
+
+    override fun cost(c: Certification, values: FilterValues, ignoreRegexps: Boolean): Boolean {
+
+        // If any inner filter returns `false`, immediately return false
+        return !this.filters.any { !it.cost(c, values, ignoreRegexps) }
+    }
+}

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/filter/IdempotentCertificationFilter.kt

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+// SPDX-FileCopyrightText: 2023 Heiko Schaefer <heiko@schaefer@name>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.wot.dijkstra.filter
+
+/**
+ * A no-op filter.
+ *
+ * This filter passes certifications through as is.
+ */
+class IdempotentCertificationFilter : CertificationFilter

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/filter/SuppressCertificationFilter.kt

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+// SPDX-FileCopyrightText: 2023 Heiko Schaefer <heiko@schaefer@name>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.wot.dijkstra.filter
+
+import org.pgpainless.wot.dijkstra.sq.Certification
+import org.pgpainless.wot.dijkstra.sq.Fingerprint
+import org.pgpainless.wot.dijkstra.sq.Path
+
+class SuppressCertificationFilter() : CertificationFilter {
+    // A certification's trust amount will be suppressed by this amount.
+    private val amount: HashMap<Pair<Fingerprint, Fingerprint>, Int> = hashMapOf()
+
+    override fun cost(c: Certification, values: FilterValues, ignoreRegexps: Boolean): Boolean {
+        amount[Pair(c.issuer.fingerprint, c.issuer.fingerprint)]?.let { suppress ->
+            values.amount = if (values.amount > suppress) {
+                values.amount - suppress
+            } else {
+                0
+            }
+        }
+
+        return true
+    }
+
+    /**
+     * Add suppression rules for all certifications along the specified path.
+     *
+     * Each edge is suppressed by `amountToSuppress`.
+     */
+    fun suppressPath(path: Path, amountToSuppress: Int) {
+        if (amountToSuppress == 0) {
+            return
+        }
+        assert(amountToSuppress <= 120)
+
+        for (c in path.certifications) {
+            val a = amount[Pair(c.issuer.fingerprint, c.issuer.fingerprint)]
+            if (a != null) {
+                val newAmount = a + amountToSuppress
+                assert(newAmount <= 120)
+                amount[Pair(c.issuer.fingerprint, c.issuer.fingerprint)] = newAmount
+            } else {
+                amount[Pair(c.issuer.fingerprint, c.issuer.fingerprint)] = amountToSuppress
+            }
+        }
+    }
+}

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/filter/SuppressIssuerFilter.kt

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+// SPDX-FileCopyrightText: 2023 Heiko Schaefer <heiko@schaefer@name>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.wot.dijkstra.filter
+
+import org.pgpainless.wot.dijkstra.sq.Certification
+import org.pgpainless.wot.dijkstra.sq.Fingerprint
+
+/**
+ * A filter that suppresses some capacity of an issuer.
+ */
+class SuppressIssuerFilter() : CertificationFilter {
+    // A certification's trust amount will be suppressed by this amount.
+    private val amount: HashMap<Fingerprint, Int> = hashMapOf()
+
+    override fun cost(c: Certification, values: FilterValues, ignoreRegexps: Boolean): Boolean {
+        amount[c.issuer.fingerprint]?.let { suppress ->
+            values.amount = if (values.amount > suppress) {
+                values.amount - suppress
+            } else {
+                0
+            }
+        }
+
+        return true
+    }
+
+    /**
+     * Add suppression rules for the issuer.
+     *
+     * Any certifications that the certificate makes are suppressed
+     * (decreased) by that amount.
+     */
+    fun suppressIssuer(issuer: Fingerprint, amountToSuppress: Int) {
+        if (amountToSuppress == 0) {
+            return
+        }
+        assert(amountToSuppress <= 120)
+
+        val a = amount[issuer]
+        if (a != null) {
+            val am = a + amountToSuppress
+            assert(am <= 120)
+            amount[issuer] = am
+        } else {
+            amount[issuer] = amountToSuppress
+        }
+    }
+}

wot-dijkstra/src/main/kotlin/org/pgpainless/wot/dijkstra/filter/TrustedIntroducerFilter.kt

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+// SPDX-FileCopyrightText: 2023 Heiko Schaefer <heiko@schaefer@name>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.wot.dijkstra.filter
+
+import org.pgpainless.wot.dijkstra.sq.Certification
+import org.pgpainless.wot.dijkstra.sq.Depth
+
+/**
+ * A filter that treats every certification as a trust signature with unconstrained depth,
+ * and no regular expressions.
+ *
+ * Note: this filter doesn't change the trust amount.
+ *
+ * This filter can be used to view a network as a 'certification network'.
+ */
+class TrustedIntroducerFilter : CertificationFilter {
+    override fun cost(c: Certification, values: FilterValues, ignoreRegexps: Boolean): Boolean {
+        values.depth = Depth.unconstrained()
+        if (!ignoreRegexps) {
+            values.regexps = null
+        }
+
+        return true
+    }
+}