# -*- mode: org -*-
# vim: syntax=c
#+TITLE: Context

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This file is written in C because it is more natural to express the context in
C than in Fortran.

3 files are produced:
- a header file : =qmckl_context.h=
- a source file : =qmckl_context.c=
- a test   file : =test_qmckl_context.c=

*** Header                                                         :noexport:
    #+BEGIN_SRC C :comments link :tangle qmckl_context.h
#ifndef QMCKL_CONTEXT_H
#define QMCKL_CONTEXT_H
#include "qmckl.h"
    #+END_SRC

*** Source                                                         :noexport:
    #+BEGIN_SRC C :comments link :tangle qmckl_context.c
#include "qmckl.h"
    #+END_SRC

*** Test                                                           :noexport:
    #+BEGIN_SRC C :comments link :tangle test_qmckl_context.c
#include "qmckl.h"
#include "munit.h"
MunitResult test_qmckl_context() {
    #+END_SRC

* Context

  The context variable is a handle for the state of the library, and
  is stored in the following data structure, which can't be seen
  outside of the library. To simplify compatibility with other
  languages, the pointer to the internal data structure is converted
  into a 64-bit signed integer, defined in the =qmckl_context= type.
  A value of 0 for the context is equivalent to a =NULL= pointer.

*** Source
    #+BEGIN_SRC C :comments link :tangle qmckl_context.c
typedef struct qmckl_context_struct {
  struct qmckl_context_struct * prev;
  uint32_t tag;
  int32_t precision;
  int32_t range;
} qmckl_context_struct;

#define VALID_TAG   0xBEEFFACE
#define INVALID_TAG 0xDEADBEEF
    #+END_SRC

  The tag is used internally to check if the memory domain pointed by
  a pointer is a valid context.

*** Test                                                           :noexport:
    We declare here the variables used in the tests.
    #+BEGIN_SRC C :comments link :tangle test_qmckl_context.c
  qmckl_context  context;
  qmckl_context  new_context;
    #+END_SRC


** =qmckl_context_check=

   Checks if the domain pointed by the pointer is a valid context.
   Returns the input =qmckl_context= if the context is valid, 0 otherwise.

*** Header
    #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_context qmckl_context_check(const qmckl_context context) ;
    #+END_SRC

*** Source
    #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_context qmckl_context_check(const qmckl_context context) {
  qmckl_context_struct * ctx;

  if (context == (qmckl_context) 0) return (qmckl_context) 0;

  ctx = (qmckl_context_struct*) context;
  if (ctx->tag != VALID_TAG) return (qmckl_context) 0;

  return context;
}
    #+END_SRC

** =qmckl_context_create=

   To create a new context, use =qmckl_context_create()=.
   - On success, returns a pointer to a context using the =qmckl_context= type
   - Returns 0 upon failure to allocate the internal data structure

*** Header
    #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_context qmckl_context_create();
    #+END_SRC

*** Source
    #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_context qmckl_context_create() {

  qmckl_context_struct*  context;

  context = (qmckl_context_struct*) qmckl_malloc ((qmckl_context) 0, sizeof(qmckl_context_struct));
  if (context == NULL) {
    return (qmckl_context) 0;
  }

  context->prev      = NULL;
  context->precision = QMCKL_DEFAULT_PRECISION;
  context->range     = QMCKL_DEFAULT_RANGE;
  context->tag       = VALID_TAG;

  return (qmckl_context) context;
}
    #+END_SRC

*** Test                                                           :noexport:
    #+BEGIN_SRC C :comments link :tangle test_qmckl_context.c
  context = qmckl_context_create();
  munit_assert_int64( context, !=, (qmckl_context) 0);
  munit_assert_int64( qmckl_context_check(context), ==,  context);
    #+END_SRC

** =qmckl_context_copy=

   This function makes a shallow copy of the current context.
   - Copying the 0-valued context returns 0
   - On success, returns a pointer to the new context using the =qmckl_context= type
   - Returns 0 upon failure to allocate the internal data structure
     for the new context

*** Header
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_context qmckl_context_copy(const qmckl_context context);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_context qmckl_context_copy(const qmckl_context context) {

  qmckl_context_struct* old_context;
  qmckl_context_struct* new_context;
  qmckl_context checked_context;

  checked_context = qmckl_context_check(context);

  if (checked_context == (qmckl_context) 0) {
    return (qmckl_context) 0;
  }

  new_context = (qmckl_context_struct*) qmckl_malloc (context, sizeof(qmckl_context_struct));
  if (new_context == NULL) {
    return (qmckl_context) 0;
  }

  old_context = (qmckl_context_struct*) checked_context;

  new_context->prev      = old_context;
  new_context->precision = old_context->precision;
  new_context->range     = old_context->range;
  new_context->tag       = VALID_TAG;

  return (qmckl_context) new_context;
}

   #+END_SRC

*** Test                                                           :noexport:
    #+BEGIN_SRC C :comments link :tangle test_qmckl_context.c
  new_context = qmckl_context_copy(context);
  munit_assert_int64(new_context, !=, (qmckl_context) 0);
  munit_assert_int64(new_context, !=, context);
  munit_assert_int64(qmckl_context_check(new_context), ==, new_context);
    #+END_SRC

** =qmckl_context_previous=

   Returns the previous context
   - On success, returns the ancestor of the current context
   - Returns 0 for the initial context
   - Returns 0 for the 0-valued context

*** Header
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_context qmckl_context_previous(const qmckl_context context);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_context qmckl_context_previous(const qmckl_context context) {

  qmckl_context checked_context;
  qmckl_context_struct* ctx;

  checked_context = qmckl_context_check(context);
  if (checked_context == (qmckl_context) 0) {
    return (qmckl_context) 0;
  }

  ctx = (qmckl_context_struct*) checked_context;
  return qmckl_context_check((qmckl_context) ctx->prev);
}
   #+END_SRC

*** Test                                                           :noexport:
    #+BEGIN_SRC C :comments link :tangle test_qmckl_context.c
  munit_assert_int64(qmckl_context_previous(new_context), !=, (qmckl_context) 0);
  munit_assert_int64(qmckl_context_previous(new_context), ==, context);
  munit_assert_int64(qmckl_context_previous(context), ==, (qmckl_context) 0);
  munit_assert_int64(qmckl_context_previous((qmckl_context) 0), ==, (qmckl_context) 0);
    #+END_SRC

** =qmckl_context_destroy=

   Destroys the current context, leaving the ancestors untouched.
   - Succeeds if the current context is properly destroyed
   - Fails otherwise
   - Fails if the 0-valued context is given in argument
   - Fails if the the pointer is not a valid context

*** Header
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_exit_code qmckl_context_destroy(qmckl_context context);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_exit_code qmckl_context_destroy(qmckl_context context) {

  qmckl_context_struct* ctx;
  qmckl_context checked_context;

  checked_context = qmckl_context_check(context);
  if (checked_context == (qmckl_context) 0) return QMCKL_FAILURE;

  ctx = (qmckl_context_struct*) context;
  if (ctx == NULL) return QMCKL_FAILURE;

  ctx->tag = INVALID_TAG;
  qmckl_free(ctx);
  return QMCKL_SUCCESS;
}
   #+END_SRC

*** Test                                                           :noexport:
    #+BEGIN_SRC C :comments link :tangle test_qmckl_context.c
  munit_assert_int64(qmckl_context_check(new_context), ==, new_context);
  munit_assert_int64(new_context, !=, (qmckl_context) 0);
  munit_assert_int32(qmckl_context_destroy(new_context), ==, QMCKL_SUCCESS);
  munit_assert_int64(qmckl_context_check(new_context), !=, new_context);
  munit_assert_int64(qmckl_context_check(new_context), ==, (qmckl_context) 0);
  munit_assert_int64(qmckl_context_destroy((qmckl_context) 0), ==, QMCKL_FAILURE);
    #+END_SRC


* Precision

  The following functions set and get the expected required precision
  and range. =precision= should be an integer between 2 and 53, and
  =range= should be an integer between 2 and 11.

  The setter functions functions return a new context as a 64-bit integer.
  The getter functions return the value, as a 32-bit integer.
  The update functions return =QMCKL_SUCCESS= or =QMCKL_FAILURE=.

** =qmckl_context_update_precision=
*** Header 
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_exit_code qmckl_context_update_precision(const qmckl_context context, const int precision);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_exit_code qmckl_context_update_precision(const qmckl_context context, const int precision) {
  qmckl_context_struct* ctx;

  if (precision <  2) return QMCKL_FAILURE;
  if (precision > 53) return QMCKL_FAILURE;

  ctx = (qmckl_context_struct*) context;
  if (ctx == NULL) return QMCKL_FAILURE;

  ctx->precision = precision;
  return QMCKL_SUCCESS;
}
   #+END_SRC

*** TODO Tests                                                     :noexport:
** =qmckl_context_update_range=
*** Header 
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_exit_code qmckl_context_update_range(const qmckl_context context, const int range);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_exit_code qmckl_context_update_range(const qmckl_context context, const int range) {
  qmckl_context_struct* ctx;

  if (range <  2) return QMCKL_FAILURE;
  if (range > 11) return QMCKL_FAILURE;

  ctx = (qmckl_context_struct*) context;
  if (ctx == NULL) return QMCKL_FAILURE;

  ctx->range = range;
  return QMCKL_SUCCESS;
}
   #+END_SRC

*** TODO Tests                                                     :noexport:
** =qmckl_context_set_precision=
*** Header 
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_context qmckl_context_set_precision(const qmckl_context context, const int precision);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_context qmckl_context_set_precision(const qmckl_context context, const int precision) {
  qmckl_context new_context;

  new_context = qmckl_context_copy(context);
  if (new_context == 0) return 0;

  if (qmckl_context_update_precision(context, precision) == QMCKL_FAILURE) return 0;

  return new_context;
}
   #+END_SRC

*** TODO Tests                                                     :noexport:
** =qmckl_context_set_range=
*** Header 
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
qmckl_context qmckl_context_set_range(const qmckl_context context, const int range);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
qmckl_context qmckl_context_set_range(const qmckl_context context, const int range) {
  qmckl_context new_context;

  new_context = qmckl_context_copy(context);
  if (new_context == 0) return 0;

  if (qmckl_context_update_range(context, range) == QMCKL_FAILURE) return 0;

  return new_context;
}
   #+END_SRC

*** TODO Tests                                                     :noexport:

** =qmckl_context_get_precision=
*** Header 
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
int qmckl_context_get_precision(const qmckl_context context);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
int qmckl_context_get_precision(const qmckl_context context) {
  qmckl_context_struct* ctx;
  ctx = (qmckl_context_struct*) context;
  return ctx->precision;
}
   #+END_SRC

*** TODO Tests                                                     :noexport:
** =qmckl_context_get_range=
*** Header 
   #+BEGIN_SRC C :comments link :tangle qmckl_context.h
int qmckl_context_get_range(const qmckl_context context);
   #+END_SRC

*** Source
   #+BEGIN_SRC C :comments link :tangle qmckl_context.c
int qmckl_context_get_range(const qmckl_context context) {
  qmckl_context_struct* ctx;
  ctx = (qmckl_context_struct*) context;
  return ctx->range;
}
   #+END_SRC

*** TODO Tests                                                     :noexport:

    
* Info about the molecular system
  
** TODO =qmckl_context_set_nucl_coord=
** TODO =qmckl_context_set_nucl_charge=
** TODO =qmckl_context_set_elec_num=

* End of files                                                     :noexport:

*** Header
  #+BEGIN_SRC C :comments link :tangle qmckl_context.h
#endif
  #+END_SRC

*** Test
  #+BEGIN_SRC C :comments link :tangle test_qmckl_context.c
  return MUNIT_OK;
}
  #+END_SRC