From e75c0cc8b5cf01c1f628ddc5fd295a6d7f423c7c Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@juliahub.com>
Date: Fri, 16 Feb 2024 12:35:01 +0530
Subject: [PATCH] feat: add `default_values` to interface

---
 docs/src/complete_sii.md         | 5 +++++
 src/SymbolicIndexingInterface.jl | 2 +-
 src/interface.jl                 | 8 ++++++++
 src/symbol_cache.jl              | 1 +
 test/symbol_cache_test.jl        | 3 +++
 5 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/docs/src/complete_sii.md b/docs/src/complete_sii.md
index e5d592a..0b795df 100644
--- a/docs/src/complete_sii.md
+++ b/docs/src/complete_sii.md
@@ -8,6 +8,7 @@ struct ExampleSystem
   state_index::Dict{Symbol,Int}
   parameter_index::Dict{Symbol,Int}
   independent_variable::Union{Symbol,Nothing}
+  defaults::Dict{Symbol, Float64}
   # mapping from observed variable to Expr to calculate its value
   observed::Dict{Symbol,Expr}
 end
@@ -77,6 +78,10 @@ function SymbolicIndexingInterface.all_symbols(sys::ExampleSystem)
     sys.independent_variable === nothing ? Symbol[] : sys.independent_variable
   )
 end
+
+function SymbolicIndexingInterface.default_values(sys::ExampleSystem)
+  return sys.defaults
+end
 ```
 
 ### Observed Equation Handling
diff --git a/src/SymbolicIndexingInterface.jl b/src/SymbolicIndexingInterface.jl
index 4edcb21..235cd85 100644
--- a/src/SymbolicIndexingInterface.jl
+++ b/src/SymbolicIndexingInterface.jl
@@ -8,7 +8,7 @@ export is_variable, variable_index, variable_symbols, is_parameter, parameter_in
        is_observed,
        observed, is_time_dependent, constant_structure, symbolic_container,
        all_variable_symbols,
-       all_symbols, solvedvariables, allvariables
+       all_symbols, solvedvariables, allvariables, default_values
 include("interface.jl")
 
 export SymbolCache
diff --git a/src/interface.jl b/src/interface.jl
index 36dac86..e7605cd 100644
--- a/src/interface.jl
+++ b/src/interface.jl
@@ -134,6 +134,14 @@ variables.
 """
 all_symbols(sys) = all_symbols(symbolic_container(sys))
 
+"""
+    default_values(sys)
+
+Return a dictionary mapping symbols in the system to their default value, if any. This includes
+parameter symbols.
+"""
+default_values(sys) = default_values(symbolic_container(sys))
+
 struct SolvedVariables end
 
 """
diff --git a/src/symbol_cache.jl b/src/symbol_cache.jl
index 5a2a81c..b923e1a 100644
--- a/src/symbol_cache.jl
+++ b/src/symbol_cache.jl
@@ -75,6 +75,7 @@ all_variable_symbols(sc::SymbolCache) = variable_symbols(sc)
 function all_symbols(sc::SymbolCache)
     vcat(variable_symbols(sc), parameter_symbols(sc), independent_variable_symbols(sc))
 end
+default_values(::SymbolCache) = Dict()
 
 function Base.copy(sc::SymbolCache)
     return SymbolCache(sc.variables === nothing ? nothing : copy(sc.variables),
diff --git a/test/symbol_cache_test.jl b/test/symbol_cache_test.jl
index 5fb1b03..5f57b12 100644
--- a/test/symbol_cache_test.jl
+++ b/test/symbol_cache_test.jl
@@ -19,6 +19,7 @@ sc = SymbolCache([:x, :y, :z], [:a, :b], [:t])
 @test independent_variable_symbols(sc) == [:t]
 @test all_variable_symbols(sc) == [:x, :y, :z]
 @test sort(all_symbols(sc)) == [:a, :b, :t, :x, :y, :z]
+@test isempty(default_values(sc))
 
 sc = SymbolCache([:x, :y], [:a, :b])
 @test !is_time_dependent(sc)
@@ -38,6 +39,7 @@ sc = SymbolCache()
 @test !is_time_dependent(sc)
 @test all_variable_symbols(sc) == []
 @test all_symbols(sc) == []
+@test isempty(default_values(sc))
 
 sc = SymbolCache(nothing, nothing, :t)
 @test all(.!is_independent_variable.((sc,), [:x, :y, :a, :b]))
@@ -46,6 +48,7 @@ sc = SymbolCache(nothing, nothing, :t)
 @test is_time_dependent(sc)
 @test all_variable_symbols(sc) == []
 @test all_symbols(sc) == [:t]
+@test isempty(default_values(sc))
 
 sc2 = copy(sc)
 @test sc.variables == sc2.variables